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Master Thesis

Sustainability & Economical Evaluation of the

Smart and Energy Efficient Technologies for

the Rammed-earth House in Accra Ghana (Case Study in Accra, Ghana)

Aslan Soltaninazarlou

Tanawut Taechakraichana

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Master of Science Thesis EGI_2016-099 MSC

Sustainability & Economical Evaluation of the Smart and Energy

Efficient Technologies for the Rammed-earth House in Accra Ghana

Aslan Soltaninazarlou

Tanawut Taechakraichana

Approved

Examiner

Jaime Arias Hurtado

Supervisor

Peter Hill

Commissioner

Contact person

Abstract

The energy consumption of buildings contributes 18% of world greenhouse gas emissions (GHG). This fact, along

with the current increase in new African buildings, leads to vast opportunities for building sustainable buildings

in Africa. The research aims to find which smart and sustainable technologies are economical and suitable for

the rammed-earth building project in hot and humid climate for sustainable development, as is the case in Accra

Ghana. Two evaluation steps were conducted - technologies evaluation and scenarios evaluation - by simulating

energy demand reduction compared to the baseline for economic evaluation in IDA Indoor Climate Energy (ICE)

software, together with Microsoft Excel and market research. Ten technologies were initially chosen and applied

to the five scenarios by consideration for economics and suitability. The result shows that four out of five

scenarios were economical. However, only two scenarios were suggested for the project - Realistic with variable

refrigerant flow air-conditioning (Realistic with VRF AC) and Economic Internet of Things (Economic IoT) - when

net present value (NPV), payback period, benefit per cost ratio (B/C), and suitability are taken into account.

Moreover, the sensitivity analysis demonstrates that the occupancy pattern affects the energy consumption to

some extent, and infiltration rate relates to energy consumption. These methods can be applied for possible

future projects, and the results can be used as a reference for projects in hot and humid climates with rammed-

earth construction.

Sammanfattning

Energiförbrukningen i byggnader bidrar 18% av världens utsläpp av växthusgaser (GHG). Detta faktum,

tillsammans med den nuvarande ökningen av nya afrikanska byggnader, leder till stora möjligheter att bygga

hållbara byggnader i Afrika. Forskningen syftar till att ta reda på vilka smart och hållbar teknik är ekonomiskt och

lämpar sig för rammade jorden byggprojekt i varmt och fuktigt klimat för hållbar utveckling, vilket är fallet i Accra

i Ghana. Två steg utvärderingsfördes - teknik utvärdering och scenarier utvärdering - genom att simulera

minskad energiförbrukning efterfrågan jämfört med baslinjen för ekonomisk utvärdering i IDA Indoor Climate

Energy (ICE) programvara, tillsammans med Microsoft Excel och marknadsundersökningar. Tio tekniker initialt

valt och tillämpas på de fem scenarier av hänsyn till ekonomi och lämplighet. Resultatet visar att fyra av fem

scenarier var ekonomiskt. Emellertid var endast två scenarier som föreslås för projektet - realistisk med variabelt

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köldmedium luftkonditionering (realistisk med VRF AC) och ekonomiska sakernas Internet (Economic IoT) - när

nuvärdet (NPV), återbetalningstid , nytta per kostnadskvot (B/C), och lämplighet beaktas. Dessutom

känslighetsanalysen visar att beläggningen mönstret påverkar energiförbrukningen i viss mån, och infiltration

avser energiförbrukning. Dessa metoder kan användas för eventuella framtida projekt, och resultaten kan

användas som en referens för projekt i varma och fuktiga klimat med rammade-jord konstruktion.

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Acknowledgement

First of all, we would like to express our utmost gratitude to Jaime Arias Hurtado - our examiner - and Peter Hill

- our supervisor - for supervising us and giving us exceedingly precious suggestions. Secondly, I would like to

thank the CEO of Asaduru company, Mohamed Bedri and the team that gave us the opportunities to work with

them and provided this interesting project. Also, we would like to give special acknowledgement to the former

architecture of Asaduru, Samer Quintana who provided us with the house design and crucial information.

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Table of Contents

Project description ............................................................................................................................................... 10

Objectives ......................................................................................................................................................... 11

Method and Approach ...................................................................................................................................... 11

Overview ...................................................................................................................................................... 12

Literature review.................................................................................................................................................. 13

Previous work ................................................................................................................................................... 13

Reflective roofs ............................................................................................................................................. 13

Green roofs ................................................................................................................................................... 15

Natural ventilation ........................................................................................................................................ 16

Insulation and windows ................................................................................................................................ 16

Orientation of the house ............................................................................................................................... 18

Indoor climate and thermal comfort ................................................................................................................ 19

PPD and PMV and Comfort Zones ................................................................................................................ 19

Relative Humidity and dew point .................................................................................................................. 21

Ventilation rate and CO2 level ....................................................................................................................... 21

Occupancy factor .......................................................................................................................................... 22

Mechanical Cooling Systems ............................................................................................................................ 22

Split type ductless air to air conditioning systems ........................................................................................ 23

Variable refrigerant flow (VRF) and multi joint cooling systems .................................................................. 24

Fan coil cooling systems ............................................................................................................................... 27

Radiant Cooling Panels ................................................................................................................................. 29

Air Handling Units and Ventilation Systems ..................................................................................................... 30

Exhaust and supply air ventilation with heat recovery (FTX system) ............................................................ 31

Humidity Control of the Fresh Air in Hot and humid Climates ...................................................................... 31

Smart Home Technologies ................................................................................................................................ 34

Lighting Automation & Daylighting utilization ............................................................................................. 35

Smart Thermostat ......................................................................................................................................... 40

Shading Automation ..................................................................................................................................... 42

Door Sensors ................................................................................................................................................. 43

The Effects of Simulation Factors ................................................................................................................. 44

Asaduru Sustainable House Project .................................................................................................................. 46

Rammed-earth construction technology ...................................................................................................... 48

Building design concept and strategies ............................................................................................................ 53

Energy demand in residential building in Ghana .............................................................................................. 53

Energy efficient house design and its characteristics ....................................................................................... 54

Modelling ............................................................................................................................................................. 55

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Indoor Climate Energy (IDA-ICE) ....................................................................................................................... 55

Baseline modelling ............................................................................................................................................ 55

Energy Simulation of Technologies ................................................................................................................... 59

Economic Evaluation of Technologies .............................................................................................................. 63

Energy Simulation and Environmental Impact Reduction of the all Scenarios ................................................. 64

Results .................................................................................................................................................................. 66

Energy Simulation and Economic Evaluation of Technologies ......................................................................... 66

Energy Simulation and Economic Evaluation of Scenarios ............................................................................... 69

The Effects of Different Factors on Energy Consumption ................................................................................ 73

Discussion ............................................................................................................................................................. 76

Conclusion ............................................................................................................................................................ 78

Future works ..................................................................................................................................................... 78

References ............................................................................................................................................................ 79

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List of Figures

Figure 1 shows the flowchart of the experiment processes ................................................................................. 12 Figure 2 shows the surface temperature of different roof material versus albedo or solar reflectance [30]...... 14 Figure 3 demonstrate the spectral characteristics of building materials and also albedo (solar reflectance) and

surface temperature for different roof materials [30] ......................................................................................... 15 Figure 4 shows windows R values versus energy consumption rate in cold climates [40]................................... 17 Figure 5 shows Various windows with different R values versus heating and cooling energy use in cold climates

[40] ....................................................................................................................................................................... 17 Figure 6 shows windows R values versus energy consumption rate in hot and humid areas [40] ...................... 18 Figure 7 shows Various windows with different R values versus heating and cooling energy use in hot and

humid climates [40] .............................................................................................................................................. 18 Figure 8 shows relationship between PPD and PMV [48] .................................................................................... 20 Figure 9 shows Summer and winter comfort zones in ASHRAE standard [48] ..................................................... 21 Figure 10 shows Heat pump/air conditioner sale in Sweden between 1982 to 2014 [56] .................................. 23 Figure 11 shows the main parts and schematic of the air to air conditioner system [55] ................................... 24 Figure 12 shows heat recovery VRF system [58] .................................................................................................. 25 Figure 13 shows standard mini VRF system [58] .................................................................................................. 26 Figure 20 shows multi joint cooling system [61] .................................................................................................. 26 Figure 15 shows two pipe fan coil unit system [62] ............................................................................................. 27 Figure 16 four pipes fan coil unit system [62] ...................................................................................................... 28 Figure 17 shows different indoor fan coil unit configurations [63] ...................................................................... 28 Figure 18 shows radiant ceiling cooling panel and its infrared image [65] .......................................................... 29 Figure 19 shows temperature variation on surface of a standard cooling panel [65] .......................................... 30 Figure 20 shows AHU and PV systems working together in a hot and humid are [68] ........................................ 31 Figure 21 shows relationship between different dew points, temperature and relative humidity at 1 bar

atmospheric pressure [72] .................................................................................................................................... 32 Figure 22 shows an heat/cool recovery air-handling unit system [71] ................................................................ 33 Figure 23 shows the overview of a FTX system [70] ............................................................................................. 33 Figure 24 shows the smart home concept applied to the project ........................................................................ 34 Figure 25 shows the example of connected light bulb [77].................................................................................. 35 Figure 26 shows wall and roof occupancy sensor [78] ......................................................................................... 36 Figure 27 shows the concept of tubular light [90] ................................................................................................ 38 Figure 28 shows the concept of designing light shelve [91] ................................................................................. 39 Figure 29 shows the Nest smart thermostat [94] ................................................................................................. 41 Figure 30 shows the Tado smart air conditioner control [100] ............................................................................ 41 Figure 31 shows an exterior venetian blind [102] ................................................................................................ 42 Figure 32 shows a window awning [102] ............................................................................................................. 42 Figure 33 shows a multi-purpose sensor [109] .................................................................................................... 44 Figure 34 shows the location of the project [18] .................................................................................................. 46 Figure 35 shows the overview of the project [19] ................................................................................................ 47 Figure 36 shows the 3D house model of 3 bedroom plan [19] ............................................................................ 47 Figure 37 shows the plan for the 3 bedrooms model house of Asaduru company [19] ...................................... 48 Figure 38 an example of Rammed earth construction [21] .................................................................................. 49 Figure 39 the process of compressing earth in rammed earth construction method [22] .................................. 49 Figure 40 shows the average temperature and precipitation of Accra Ghana [117] ........................................... 50 Figure 41 shows the seasonal temperature range of Accra Ghana[117] ............................................................. 50 Figure 42 shows the wind speed of Accra Ghana [117] ........................................................................................ 51 Figure 43 shows relative humidity in Accra Ghana [118] ..................................................................................... 51 Figure 44 shows the dew point of Accra Ghana [118] .......................................................................................... 52 Figure 45 shows the solar irradiation on the project [19] .................................................................................... 52 Figure 46 shows the overview of Kyoto Pyramid [23] .......................................................................................... 53

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Figure 47 shows the 3D energy model of 3 bedroom house imported to IDA-ICE [19] ....................................... 55 Figure 48 shows the cooling set point in living room for one day ........................................................................ 60 Figure 49 shows the temperature set points used in the technologies evaluation for fan coil system ............... 62 Figure 50 shows the total energy consumption of the technologies ................................................................... 66 Figure 51 shows the energy reduction of the technologies ................................................................................. 67 Figure 52 shows the incremental investment cost of technologies ..................................................................... 67 Figure 53 shows the net present value of the technologies ................................................................................. 68 Figure 54 shows the payback period of the technologies .................................................................................... 68 Figure 55 shows the benefit to cost ratio of the technologies ............................................................................. 69 Figure 56 shows the energy reduction of the scenarios ....................................................................................... 70 Figure 57 shows the incremental investment cost of the scenarios .................................................................... 70 Figure 58 shows the net present value of the scenarios ...................................................................................... 71 Figure 59 shows the payback period of the scenarios .......................................................................................... 71 Figure 60 shows the benefit per cost ratio of the scenarios ................................................................................ 72 Figure 61 shows the CO2 reduction from the scenarios ....................................................................................... 72 Figure 62 shows the effect of type of occupancy schedule on energy consumption ........................................... 73 Figure 63 shows the effect of variable fixed ACH on the energy consumption in comparison with baseline ..... 74 Figure 64 shows the effect of variable fixed ACH on CO2 level ............................................................................ 74 Figure 65 shows the effect of variable fixed ACH50 on the energy consumption ............................................... 75 Figure 66 shows the effect of variable ACH50 on CO2 level ................................................................................. 75

List of Tables

Table 1 shows the zones geometry ...................................................................................................................... 56 Table 2 shows the rammed-earth properties ....................................................................................................... 56 Table 3 shows U-value and thickness of building envelop ................................................................................... 57 Table 4 shows the glazing properties ................................................................................................................... 57 Table 5 shows the windows size and quantity ..................................................................................................... 57 Table 6 shows the zones area and number of light bulbs .................................................................................... 58 Table 7 shows the cooling capacity in the baseline .............................................................................................. 58 Table 8 shows the properties of exterior Venetian blind ..................................................................................... 61 Table 9 shows the designed cooling power for different zones of the three-bedroom house for fan coil system

.............................................................................................................................................................................. 62 Table 10 shows the maximum designed cooling power (W) and chilled water mass flow rates (kg/s) in the

different zones of three-bedroom house using cooling panels ............................................................................ 63 Table 11 shows the financial parameters ............................................................................................................. 64 Table 12 shows the initial and changing rate of discounted rate and electricity price in Ghana ......................... 64 Table 13 shows the range and median of equipment price ................................................................................. 64 Table 14 shows the technologies applied to scenarios ........................................................................................ 65 Table 15 shows the factors and factors range ...................................................................................................... 73

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Nomenclature

Abbreviation

AC Air Conditioning

ACH Air Change rate

AHU Air Handling Unit

BIM Building Information Modelling

B/C Benefit per Cost Ratio COP Coefficient of Performance

COP2 Cooling Coefficient of Performance

CO2 Carbon Dioxide

FTX Från och Tillluft Värmeväxling-Supply and Exhaust Air Heat Exchanger

GHG Greenhouse Gas

GWP Global Warming Potential

HVAC Heating, Ventilation and Air-conditioning

ICT Information and Communication Technology

ICE Indoor Climate and Energy

IOT Internet of Things

LED Light Emitting Diode

PIR Passive Infrared

PVent Personal Ventilation

PV Photovoltaic

PPD Predicted Percentage of Dissatisfied index

PMV Predicted Mean Vote index

RFID Radio Frequency Identification

SEMS Energy Management Systems

UN United Nation

U value Rate of transfer of heat through a structure divided by the difference in temperature across

that structure VRF Variable Refrigerant Flow

WWR Windows to Wall area

Symbol

Al Area of Utilization [m2]

C Corrected Cooling Consumption [kWh/year]

Cu Coefficient of Utilization

Fc Lighting Cooling Factor [kWh/year]

F Future Value [USD]

I Lighting Output [lux]

i Interest Rate [%]

L Lighting Energy Reduction [kWh/year]

Li Total illumination [lux]

LLF Lighting Loss Factor

n Considered Period [Year]

P Present Value [USD]

Pa Pressure [Pascal]

S Simulated Cooling Consumption [kWh/year]

T Total Cooling Consumption [kWh/year]

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Project description

Awareness of global warming has become increasingly important in this era. Greenhouse gases (GHG) emissions,

a major influence on global warming, are mainly emitted from energy consumption of the residential sector,

which is 18% of the world GHG, 21% in the United States[1] and 23% in Australia [2] . Globally, the urban

population will increase to five billion or 60% of the world population by 2050 [3], and will lead to an increase

of energy consumption in the residential area, especially, in developing countries in Asia and Africa continents.

Because of these reasons, developing countries in the region need to be sustainably planned. The population in

Africa is counted to be around 1.2 billion, which was projected to reach 2.5 and 4.4 billion in 2050 and 2100

respectively [4]. Currently, 60% of the African population does not have access to energy with annual 7 %

increase of urban energy demand. The United Nations (UN) set up the global challenge by guaranteeing that the

world can have access to modern energy by 2030, and will increase energy efficiency and renewable utilization

by double [5]. Moreover, buildings' energy consumption is considered as 56% of the total African energy

consumption which is 75% of the electricity generation [5]. The rapid increase in energy demand causes an

energy deficit in the region. However, the forecast by [5] reveals the potential of improving building energy

consumption since about 75% of the buildings will be newly built according to the forecast. Therefore, the supply

of future energy consumption needs to be thought carefully in the most effective way. These issues can be

tackled by applying current and future technologies such as using heat pumps, sustainable and energy efficient

house design and an integration of information and communication technologies (ICT). However, the main factor

that a house owner and engineers need to consider before implementation is the economic feasibility. However,

there is no clear picture of the overall technologies of smart and sustainable and energy-efficient house both

individually and wholly as a system. End users and engineers find it difficult to decide which technologies are

economical and worthy to invest in, particularly for a future project.

Asaduru is a Swedish company focusing on sustainable development with expertise in rammed earth

construction, which gives more advantages than the traditional way of construction using concrete. Rammed-

earth is an environmental friendly construction method from cradle to grave since it uses mostly local materials

like soil, sand and sometime stabilizer like cement. In addition, it has a good thermal mass capacity with an

average U-value (average heat transfer coefficient like concrete) without insulation layer in between. The

company pursues to develop a project as a model for sustainable houses in Ghana, Africa. The company aims to

develop 20 houses to supply the upper-middle class in Ghana with a sustainable community prototype, and

plans to develop a project for the low-middle class in the future since Africa lacks several million households.

The project will combine sustainable construction, sustainable house and smart home concepts to develop the

most efficient and affordable house model focused on self-sufficient communities and zero/low GHG emission.

The similar energy efficient house projects conducted in hot dry and hot humid climates shows that the interior

temperature in the houses can be reduced by the utilization of various passive techniques like window shading,

natural ventilation, choosing convenient orientation, thermal energy storage systems, evaporative cooling, night

ventilation, night sky radiation cooling and thermal inertia. All of these techniques result in increased comfort

inside the houses [6], [7]. In the same way as, the internet of things is used to control alongside with an efficient

and economical cooling system and ventilation for achieving the lowest energy demand as possible for

implementation in rammed-earth house, which is already well-known for using a sustainable material.

This research will be prepared for Asaduru under Royal Institute of Technology's supervision, which aims to

evaluate the breakeven point of different technologies in the market to combine as scenarios for simulating the

energy reduction of technologies and scenarios compared to the baseline. These studied technologies will be

considered for the project plan before construction.

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Objectives

The main objective of this thesis is to consider the appropriate systems to be applied to the rammed-earth

houses project in Accra, Ghana from a techno-economic point of view. To achieve the objective, some sub-

objectives need to be done as follows.

- Study the main principle of the technologies for applying to the building at Asaduru sustainable house

project.

- Develop different scenarios to evaluate the most appropriate technologies for the sustainable

buildings.

- Evaluate energy performance for different scenarios in order to assess the energy reduction, costs and

environmental impact.

Method and Approach

The literature reviews of Accra's climate condition, smart and sustainable technologies, rammed-earth

construction and market research of the technologies were investigated. The house model was provided by

Asaduru. The energy simulation using IDA-ICE version 4.7 with student license is followed by an economic

evaluation of technologies and scenarios as a system using Microsoft Excel financial functions, along with market

research and basic assumptions. The IDA-ICE makes use of the best and latest building energy model available

along with variable time step instead of "hand code component subroutines" [8]. Furthermore, the software is

capable of adapting the controlled strategy, which enables the users to apply basic control principles. The IDA-

ICE is believed to be a suitable software for both non-existing and existing projects for energy demand simulation

by applying different technologies and controlled strategies. The building information and basis of smart device

principles applied to the simulation were obtained from literature review. The weather data were taken from

Energy Plus website, which conducts real measurement of weather in a number of different countries. The latest

weather file in March 2016 was used in the simulation.

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Overview

FIGURE 1 SHOWS THE FLOWCHART OF THE EXPERIMENT PROCESSES

The processes of the experiment are shown in Figure 1. The process starts with data collection to obtain the

available technologies in the market for applying in the simulation software IDA Indoor Climate and Energy (ICE).

The energy simulation, economical evaluation and suitability were conducted to initially obtain an idea of which

technologies will be put into the different scenarios. After the selection of the technologies in to three scenarios-

Realistic, Highest Energy Reduction and Economic, energy simulation and economical evaluation, again, will be

conducted to be able to decide that which technologies best match to the projects.

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Literature review

The first step of methodology is to review different technologies, which would be applied in the project. Different

passive-energy efficient and smart systems will be discussed and reviewed for their principles, price and the

products available in the market. Not all of them may be implemented in this project, but can be a good guideline

to the future works in this field. Moreover, some previous similar projects will also be evaluated.

Previous work

A research by Torunski et al. [9] discusses the potential of energy saving when smart systems are applied. Four

methods were compared, from which three of them are actual measurements. Only one simulation method,

which is done by University of Karlskrona, was stated in the paper. A research by Hussain et al. [10] displays the

potential of home automation on energy saving by measuring energy consumption in four houses before and

after the installation. It found out that home automation could decrease energy consumption by 18.7%;

however, the site location, weather and house material were not defined. Several years later, the Energy

Management System (SEMS) was purposed by Park et al. [11] who experimented on a system that consists of

sensors, a home management system and three appliances using wireless communication. Some research

examines single smart devices; for example, a lighting schedule using “life log data” was investigated in Yang et

al. [12] for evaluating lighting energy consumption in smart houses. There are many types of simulation software

used for energy consumption simulation. In 2015, there was a research by Shoubi et al. [13] that tried to reduce

energy demand by applying the simulation software. The study aims to find an alternative material for reducing

a building's energy demand using Building Information Modelling (BIM). A double floors house in Johor, Malaysia

was a case study that suggested an alternative design for the project. Another research by Mehdiand et al. [14]

investigated and optimized electricity consumption for appliances, which were differentiated into four types of

appliances, using mathematical models. One interesting and well-known simulation software is IDA Indoor

Climate and Energy (IDA-ICE). The software is appropriate for incorporating HVAC and lighting systems with a

controlled strategy of the technologies. One research by Hilliaho et al. [15] investigated the appropriateness for

IDA-ICE to simulate energy consumption of glazed space compared to the actual measurements. Recently, a

research applied IDA-ICE to investigate the effects of the traditional assumption on the returned temperature

of the heating system [16]. The result shows a good approximation. Moreover, research by Taylor et al. [17]

shows the energy consumption of rammed-earth offices compared to concrete offices. It said that there is a high

possibility for the energy consumption reduction to be well designed and that the control strategy could be

changed. However, none of the research were conducted for a future project with rammed earth construction,

adapted not only for controlled strategy, but also for cooling demand in a hot and humid climate with the best

thermal comfort, and considered all the technologies as a system in regards to economical point of view.

Therefore, the objective of this thesis is in the following section.

Reflective roofs

Unlike the regions located in the northern hemisphere, which normally are in need of both cooling and heating,

most of the tropical or subtropical areas such as the location of our project in Accra, mostly are in need of

cooling. This is the main concern in construction of the houses in tropical and hot-humid climates [26].

Since the majority of the heat gain which is originated from solar irradiation is coming from windows, roof and

walls, passive cooling techniques can be implemented to the envelopes to reduce the cooling demand without

compensation with large amounts of valuable energy [27]. Passive cooling techniques are mostly preventive

measures against increasing the temperature inside the buildings. According to Asimakopoulos et al. [28], the

reflective cooling technique is mainly aimed to slow down the heat transfer into the building. The reflective roof

technique which is investigated by Givoni et al. [29] showed a promising effect in terms of reducing heat transfer

through the roof to the entire envelope. Also, the color and thermo-physical properties (solar reflectance and

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thermal emittance) of the roof material have a huge effect on external surface temperature. Figure 2 and Figure

3 demonstrate the impact of roof material and roof color on albedo or solar reflectance and also on surface

temperature. The measurements are conducted in same outdoor condition and it is clear that utilizing light

colors like white and grey can maintain the surface temperature at lower rates rather than dark colors like black

which has almost 100% hotter surface temperature.

FIGURE 2 SHOWS THE SURFACE TEMPERATURE OF DIFFERENT ROOF MATERIAL VERSUS ALBEDO OR SOLAR REFLECTANCE

[30]

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FIGURE 3 DEMONSTRATE THE SPECTRAL CHARACTERISTICS OF BUILDING MATERIALS AND ALSO ALBEDO (SOLAR REFLECTANCE)

AND SURFACE TEMPERATURE FOR DIFFERENT ROOF MATERIALS [30]

Moreover, Akbari et al. showed that increasing the solar reflectance of the roof material from 0.1 to 0.35 can

decrease the cooling demand by approximately 7 % inside the envelope [30]. Still, accumulation of dust and dirt

on reflective roofs can reduce the reflectance factor and increase the maintenance. Visual discomfort is another

aspect to take into consideration for reflective roofs.

However, nearly all the researches that were implemented to find out the effect of the reflective roofs are from

countries with hot and dry climate. Thus, more investigations must be done in hot and humid regions like Accra,

Ghana to understand the effect of cool roofs [26], [31] .

Finally, according to Stetiue et al., reflective and radiative cool roof techniques are among the most effective

and cost competitive measures in terms of cooling energy reduction methods. This positive contribution can

reach to 42% in hot arid areas and to 17 % in humid regions [32].

Green roofs

One of the well-consolidated methods to reduce the cooling demand inside the buildings is the green roof

technique. This technology is able to not only generate considerable energy savings but also improve the thermal

performances of the building and provide other ecological benefits [33], [34].

While according to Bevilacqua et al. [34] green roof technique can decrease the surface temperature of the roof

by 12C in the hot and arid climate of Southern Italy-Calabria, it only can decrease the roof surface temperature

in a hot and humid region like Hong Kong by 5.2C [35].

This research clearly shows the difference between the green roof effect in hot and humid versus hot and dry

climates. Obviously, the effect of the green roof on cooling energy reduction is much higher for hot and dry

climates in comparison to hot and humid ones. This crucial factor should be taken into account when the green

roof technique is going to be implemented in the project in Accra , Ghana with high humidity all over the year.

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Moreover, Jim et al. demonstrated that the cooling effect of the green roof is diminishing on rainy and cloudy

days in contrast with sunny days [35].

Beside all above, according to Lamnatou et al. [33]. the combination of Photovoltaic panels (PVs) with green

roofs technique which can be a novel method in the construction sector, may provide advantages like an increase

in PV output due to interaction between PV and plantation. This is mainly due to slightly lower temperatures

under or around PV panels, which play a crucial role to increase the PV panel efficiency especially in hot seasons.

Natural ventilation

The two main natural ventilation systems can be named as wind catchers and cross ventilation. However,

according to some surveys higher relative humidity has a negative effect on cooling energy demand reduction

in hot and humid areas. Zhang et al. [36] clearly demonstrated that at the outdoor temperatures of over 28 °C

and relative humidity above 70%, the indoor temperature of the building will rise by 0.4 °C for every 10% increase

of relative humidity. While the average relative humidity level in Accra is around 76 to 86% around the year and

wind velocity is not so high either, utilizing the natural ventilation methods to decrease the cooling demand is

not seemingly useful. In the other words, opening the windows and doors to allow the outdoor fresh air to

infiltrate the indoor area will directly affect the cooling demand negatively in almost all months in Accra [7], [37].

Another research which is done by Aflaki et al. [38] demonstrated that high humidity levels, persistent cloud

cover and low temperature differences between day and night are among the main constraints against the use

of natural ventilation as a prevalent strategy in hot and humid climates. The maximum effect of natural

ventilation can be achieved when it relies on some strategies to avoid heat gain in envelopes. In other words,

limiting the solar absorption of the house, window to wall and window to floor ratio measures, house orientation

and design are the main factors which should be taken into consideration in projects that will be constructed in

hot and humid areas [38].

Insulation and windows

One of the important strategies for building energy conservation is insulation of the building envelope for both

opaque and transparent structures. By this, insulation of the different parts of the house such as roofs, walls,

floor and even foundation can be defined as essential factors of an energy efficient house. Furthermore, having

better insulation in transparent areas like windows and skylights can reduce the heating and cooling energy loss

in the buildings. Also, it is documented that the thickness of the insulation layers has a big impact on savings

which are achieved by reduction in energy use. According to Karlsson et al. [39], it is still uncertain how much

insulation is the optimum for reducing the energy consumption in a single family house. Nevertheless, most of

the surveys showed that insulation has a minor role in hot climates regarding saving cooling energy inside the

house. In other words, the benefit of insulation in hot and humid climate is too low in comparison to cold

climates [40], [41].

Also, the heat gain in hot and humid areas are mainly coming from solar radiation and conduction through

windows, infiltration and conduction through walls and roof. While these are referring to outdoor condition and

temperature, internal heat gains from electrical appliances, occupants and lighting stand for about one third of

the total heat gain in a single family house.

Something which is worth to know about wall and roof insulation strategies in hot and humid areas is that the

insulation does not have a significant role regarding cooling demand reduction in the building. Kim et al.[40]

clearly showed that decreasing the U value of the wall insulation in a hot and humid area like Florida in the US

will just decrease the home energy consumption slightly. This is almost the same for roof insulation strategies

[42]. In overall, adding insulation layers to the building envelope in hot and humid climates will insignificantly

change the cooling demand.

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To our knowledge the effect of windows glazing and insulation is much better for cold climates rather than hot

climates. Kim et al. [40] showed that in cold climates, triple glazing window with a U value of 1.65 W/m2K

consumes 50% and 18% less energy in comparison with single glazed window with a U value of 5.68 W/m2K and

double glazed window with a U value of 2.84 W/m2K, respectively. In other words, in cold climates, increasing

the insulation layers and air/gas gaps between window glazing directly affect the energy consumption inside the

buildings. Nevertheless, the positive effect of the increased glazing is mostly seen for heating demand and it can

reduce the heating energy and not cooling demand. Figure 4 and Figure 5 demonstrate the energy consumption

rate against windows R-values (R-value=1/U-value) and heating/cooling energy consumption for various

windows R-values, respectively, in cold climates.

FIGURE 4 SHOWS WINDOWS R VALUES VERSUS ENERGY CONSUMPTION RATE IN COLD CLIMATES [40]

FIGURE 5 SHOWS VARIOUS WINDOWS WITH DIFFERENT R VALUES VERSUS HEATING AND COOLING ENERGY USE IN COLD

CLIMATES [40]

On the other hand, when increasing the windows insulation and glazing in hot and humid areas are discussed, it

came up with an interesting result. Windows with U value of 5.68 W/m2K and 0.57 W/m2K have nearly identical

heating and cooling energy consumptions [40]. It means that utilizing single/double glazed windows in hot and

humid regions like Accra is more appropriate regarding energy savings and economical aspects.

18

Eventually, the negligible role of better insulation in walls, roof and windows in hot and humid areas is mainly

due to the small temperature difference between indoor and outdoor temperatures. Figure 6 and Figure 7 show

the correlation between various windows with different R values with heating and cooling energy use in hot and

humid areas of the US.

FIGURE 6 SHOWS WINDOWS R VALUES VERSUS ENERGY CONSUMPTION RATE IN HOT AND HUMID AREAS [40]

FIGURE 7 SHOWS VARIOUS WINDOWS WITH DIFFERENT R VALUES VERSUS HEATING AND COOLING ENERGY USE IN HOT AND

HUMID CLIMATES [40]

Orientation of the house

It is widely known that house orientation is among the crucial factors which can affect the energy consumption

in buildings, positively or negatively, depending on the house location and solar orientation [43], [44]. While in

cold climates, facing the buildings toward more solar radiation is more desirable, in hot climates this should be

reversed where solar radiation should be avoided to leak through the envelope. According to surveys done by

some passive house research groups, an energy saving of 20 to 36% can be achieved if correct landscape,

location and orientation is chosen for the buildings [45].

The house orientations which face South and Southeast have the benefits of free solar gains and free lighting

during some hours a day for areas located in northern hemisphere. This is because that sun is shining from

19

Southeast to Southwest with a slight angle during a whole year in northern hemisphere. Conversely, sun shines

from Northeast to Northwest in southern hemisphere [46]. Although, depending the construction company's

desire and customers request the orientation, shape and plan of the houses can be changed regardless of their

role on energy consumption of the building.

Indoor climate and thermal comfort

According to ASHRAE, thermal comfort can be defined as “the condition of mind that expresses satisfaction with

the thermal environment”. The judgment of thermal comfort depends on many inputs influenced by physical,

physiological, psychological, and other processes affected by occupants [47].

Humans have a very effective, complex and not fully understood unconscious temperature regulatory system.

This system is working to hold the body core temperature at 37°C according to metabolism, respiration, blood

circulation near the skin surface and sweating. Obviously, there are some environmental factors which affect

the sense of thermal comfort in humans that are; temperature, air velocity, humidity and radiation. In addition,

the upper limit for the wet bulb temperature or severe heat stress for both unclothed and clothed individuals is

around 30°C at air speeds of 0.1 to 0.5 m/s [47]. On the other hand, acquiring the correct and desirable indoor

temperature and relative humidity level implementation of mechanical or passive cooling systems like AHU or

AC is necessary. These systems will be explained in detail in the next parts of the report.

Beside all above, to get an optimum indoor air quality (IAQ) in buildings, ventilation systems and air infiltration

play a crucial role. By this, occupants can achieve; a better thermal regulation, in and outdoor pollution control

and desirable fresh air [47].

PPD and PMV and Comfort Zones

Getting back to the basic definition of the thermal comfort for occupants we can define the Predicted Percentage

of Dissatisfied index (PPD) and Predicted Mean Vote index (PMV) values. These values, which are defined by

Fanger (Fanger 1970) can be used " to predict mean value of subjective rating of a group of people in a given

environment". This is mainly due to variation of the thermal comfort sense for different individuals. According

to Fanger, PMV values between +1 and –1 are acceptable, while values higher than +1 or lower than –1 are not

desirable and are counted as dissatisfaction limits. The formula for PMV is shown below.

EQUATION 1 FORMULAR FOR PMV

𝑃𝑀𝑉 = (0.303𝑒−0.036𝑀 + 0.025)𝑥[(𝑀 − 𝑊) − 𝐻 − 𝐸𝑐 − 𝐶𝑟𝑒𝑠 − 𝐸𝑟𝑒𝑠] (1)

Where M - metabolic rate, W/m2

W - effective mechanical power, W/m2 H - dry heat loss, heat loss from the body surface through convection, radiation and conduction, W/m2

Ec - evaporative heat exchange at the skin, when the person experiences a sensation of thermal neutrality, W/m2

Cres - respiratory convective heat exchange, W/m2

Eres - respiratory evaporative heat exchange, W/m2

Another Fanger value, which is called PPD, can be used to predict the number of individuals who are not satisfied

with a given thermal condition. As it is shown in Figure 8, PPD of 10% corresponds to PMV of ±0.5 which is widely

accepted as a scale for thermal comfort in the world [47], [48].

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FIGURE 8 SHOWS RELATIONSHIP BETWEEN PPD AND PMV [48]

These two values will be used in our project to show the thermal satisfaction for every zone in the house.

Furthermore, in order to understand and achieve the thermal environmental conditions for human occupancy,

there is a standard of ASHRAE 55, which expresses the comfort conditions or zones for at least 80% of the

sedentary or slightly working occupants who find that zone thermally comfortable and acceptable. This standard

scale includes winter and summer seasons with CLO values of 0.9 (0.14 m2.K/W) and 0.5 (0.078 m2.K/W),

respectively. Figure 9 shows the chart for ASHRAE summer and winter comfort zones.

21

FIGURE 9 SHOWS SUMMER AND WINTER COMFORT ZONES IN ASHRAE STANDARD [48]

Relative Humidity and dew point

Relative humidity or RH can be defined as a "ratio of partial pressure of the water vapor in the air to the pressure

of the saturated vapor at the same temperature" [48].

The RH percentage is mainly useful when the dry bulb temperature is known for the specific condition. According

to most of the literatures and ASHRAE handbook the standard RH value for indoor condition is around 50% at

21°C. However, in order to avoid condensation on cold surfaces we may need to maintain the RH value lower

than 50% depending on the indoor environment conditions. That is why we need to define another variable

called the dew point. The dew point is an atmospheric temperature (depending to pressure and humidity) below

which water droplets start to condense and dew can form. It is also a tool to measure the humidity of the

environment. At the dew point temperature, the saturated water vapor pressure is equal to the ambient vapor

pressure. Below the dew point, saturated water vapor will begin to condense on solid surfaces that are colder

than dew point temperature. It is worth to know that due to commonly high relative humidity levels in Accra,

specific measures and cooling strategies should be considered for the designed houses [47]–[49].

Ventilation rate and CO2 level

It is documented that in order to acquire optimum air quality and thermal comfort in buildings, utilizing and

implementing ventilation are an important role. This is mainly due to the accumulation of undesired pollutants

derived from the occupants’ activities inside the building that consequently lead to the need for introducing a

reasonable amount of fresh air and removing aged air from the building. In other words, while the building is

22

being designed, infiltration and ventilation rates should be taken into consideration to get the desired indoor air

quality (IAQ). In accordance with ASHRAE Standard 62, the minimum fresh air ventilation per person for any type

of building is 8 l/s which is able to dilute the CO2 concentration inside the envelope and maintain it around 700

ppm. This concentration is nearly the same as the typical CO2 generation rate per person inside a closed

envelope. Although, CO2 is not counted as a hazardous or toxic gas inside the building, it should be diluted

accordingly to achieve a desirable IAQ. Nevertheless, the recommendations for CO2 level in ASHRAE standard 62

for different building types are for classrooms and conference rooms 15 cfm (7 l/s) per occupant. For office space

and restaurants 20 cfm (9.5 l/s) per occupant is recommended and for hospitals, it is 25 cfm (12 l/s) per occupant.

[1 cfm (ft3/min) = 1.7 m3/h = 0.47 l/s] [47], [48], [50].

Also, the minimum ventilation rate for a building is 0.35 l/s.m2 of living area with regard to Swedish house

regulation standards [51]. This is the minimum amount of outside fresh air ventilation rate if there is occupancy

in the room or zone, otherwise, the ventilation rate should be around 0.10 l/s.m2 of living area. This clearly

shows that even though the building can be unoccupied in some hours of the day, the ventilation system should

provide some amount of fresh air to the zones. Furthermore, it is recommended that buildings and envelopes

are exposed to forces of ventilation or airing at least once a day [51].

Occupancy factor

Occupancy and rate of the occupancy are among the most effective and crucial factors in building design,

operation and maintenance. While occupancy can influence the lighting, ventilation, indoor air quality (IAQ) and

temperature, it should be elaborately predicted and surveyed before the house construction phase starts [47].

For instance, overestimating the occupancy rate inside the buildings can lead to oversizing of the mechanical

cooling systems and thus over predicting cooling loads. This can also lead to misinterpretation of the building

energy performance simulations. Ding et al. [52] documented that with a proper occupancy schedule the cooling

demand for the building can be reduced by 36%.

However, interior disturbance arising from occupant behavior is accounted as the main hindrance and

uncertainty in order to get an elaborate prediction over occupancy schedule. Another survey that is conducted

by Carlucci et al. [53] showed that different occupancy schedules have a statistically significant influence on the

building’s energy performance, especially cooling energy demand. However, the effect of occupancy schedule

is seen more in high-performance buildings rather than poorly insulated buildings. Thus, despite high costs and

modeling time, more detailed and precise description of occupancy and occupant-dependent input variables is

required in order to get an accurate energy and performance modeling for a high-performance building [53].

Mechanical Cooling Systems

Unlike passive cooling systems where mechanical parts like pumps, fans or compressors are mainly avoided,

active cooling/heating systems have some running parts that allow users to maintain the indoor climate in a

desirable and acceptable level. Generally, the heat and cooling transmitting process can be done by means of

convective systems like warm air systems and convector systems (heat pump/air conditioning and fan coil),

convective and radiative systems like floor heating systems and radiator systems and finally radiative systems

like ceiling heating/cooling systems. To our knowledge, convective systems have more priority due to providing

more evenly distributed heat/coolness inside the envelope in comparison with radiative systems, which are used

mainly to cover local heating/cooling demand. Accordingly, the energy consumption of the former systems is

generally more than the latter.

However, the mechanical cooling systems can be divided into three main categories of; all air systems, air and

water systems and all water systems [47], [48].

23

Split type ductless air to air conditioning systems

Generally, the majority of home and small commercial air conditioning systems utilize and circulate refrigerant

in a closed “split” system to cool/heat and condition inside air. In case of cooling, outdoor air is the medium

used to re-cool and condense the refrigerant. In turn, the cooled refrigerant is pumped to indoor evaporator

unit to take the heat from the space and cool down the room [54], [55]. Figure 10 shows the yearly sold air to

air heat pump/air conditioner systems in Sweden from 1982 to 2014. Other types of the heat pumps like air to

water, air to brine and supply air heat pumps are shown too. Only in 2008, more than 75,000 air to air heat

pump/air conditioner have been sold which clearly shows the popularity of this product. Also, there is a lack of

statistical information for air to air heat pump selling rate between 2012-2014[56].

FIGURE 10 SHOWS HEAT PUMP/AIR CONDITIONER SALE IN SWEDEN BETWEEN 1982 TO 2014 [56]

Compressor is the heart of the system and can be reciprocating, scroll or screw type. There is a four-way valve

located at outdoor unit after compressor which switches the cooling and heating direction when it is needed.

The condenser coil is the outside unit in case of cooling. Outdoor and indoor fans pull and blow air from and to

the atmosphere, respectively The evaporator coil is the inside unit in case of cooling and other minor parts like

water drainage system and filters. Figure 11 shows the main components of a split-type air to air heat pump/air-

conditioner.

24

FIGURE 11 SHOWS THE MAIN PARTS AND SCHEMATIC OF THE AIR TO AIR CONDITIONER SYSTEM [55]

This popular cooling system has some pros and cons, which should be taken into consideration especially in such

projects that visual impact of the house auxiliary systems like cooling apparatus is important for clients and

construction companies.

Since these systems' hearts are located at outside of the house, operation and maintenance can be carried out

easier during lifetime of the system. In other words, piping, compressors, fans, wiring system and noise

producing parts are separated from the indoor unit, which in turn may reduce the inconvenience to the

occupants. Another advantage is that they are ductless, and the interior unit is completely inside the thermal

shell [57]. Moreover, seasonal changes cannot affect the cooling process especially in a hot and humid climate

like Accra with an even outdoor temperature around the year. Dehumidifying is among the main advantages of

these systems, which enables the end users to feel comfortable in hot and humid climates. Visual impact of the

air to air conditioner is not the only drawback of these systems. This can be more complicated if the house owner

wishes to install more than one split type AC in his/her house[48], [54].

Variable refrigerant flow (VRF) and multi joint cooling systems

The next generation of the split type air to air conditioning systems can be called variable refrigerant flow or VRF

cooling/heating systems, which is used in residential and commercial buildings. This technology has been widely

used in Japan formerly, and it has reached the European and American markets in 1987. These systems have

been implemented in more than 50% of medium-sized commercial and residential buildings and 33% of large

commercial buildings in Japan. Similar to split AC systems, cooling or heating energy is transferred to or from

the space directly by circulating refrigerant (different refrigerant types like R410A with inverter technology can

25

be used) to evaporators or indoor units located near or within the conditioned space. VRF technology is more

complex, sophisticated and flexible in comparison with ductless split and ductless multi joint (multi split AC

systems) conditioning systems. Also, they have larger capacities starting from 11 kW to 200 kW capacities

depending on the cooling/heating requirement of the buildings. Capability of connecting the outdoor unit/units

to several indoor (evaporator in cooling case) units with just one main piping line, having multiple compressors

and complex oil and refrigerant management and control systems can be considered as the superiorities of these

systems when compared to the old and conventional split AC systems.

Considering the VRF term, it is referred to "the ability of the system to control the amount of refrigerant flowing

to each of the evaporators, enabling the use of many evaporators of differing capacities and configurations,

individualized comfort control, simultaneous heating and cooling in different zones, and heat recovery from one

zone to another" [58]. Some advantages of these systems are; lightweight of every modular unit in comparison

with chillers and extendibility of the VRF systems to cover large cooling/heating loads of hundreds of kilowatts,

and the design flexibility of the VRF system where as one condensing unit (outdoor unit) can be easily connected

to up to 20 indoor evaporating units (indoor unit) with different capacities from 1.75 kW up to 14 kW and

different configuration like ceiling recessed, wall-mounted, floor console. Also, for buildings and envelopes

requiring simultaneous heating and cooling VRF can be a good choice. In contrast with multi split AC systems,

while one zone utilizes cooling another zone can take the benefit of heating at the same time. Extra heat

exchangers which are located in distribution boxes are utilized to transfer some reject heat from the

superheated refrigerant exiting the zone to be cooled to the refrigerant that is going to the zone to be heated

[58].

Energy efficiency of the VRF AC systems is generally dependent on various factors like climate, type of project,

occupancy regime and comparison method. While some research showed that the cooling energy savings by

VRF systems utilizing R410A as refrigerant and inverter technology in relatively temperate Brazilian climate may

reach to 30%, others showed a little or no savings compared to the conventional water or air-cooled chillers.

The main factor of savings by VRF systems are due to their high part-load efficiency. Another aspect of the VRF

systems can be seen when energy losses are considered in the ducting system. According to ASHRAE Standard

around 10% of the energy is getting lost inside the ducts in ducted HVAC systems. VRF systems do not need any

kind of duct and utilize the evaporative cooling of refrigerant sent by small pipes directly to the needed zone

[59]. Figure 12 and Figure 13 demonstrate heat recovery VRF system and standard VRF system, respectively.

FIGURE 12 SHOWS HEAT RECOVERY VRF SYSTEM [58]

26

FIGURE 13 SHOWS STANDARD MINI VRF SYSTEM [58]

Multi joint or multi split cooling/heating systems have the same principle of working as one to one split type AC

systems. The only difference is that in this technology ‘multiple’ evaporator units can be connected to one

external condensing unit. This system can easily replace the ducted cooling systems due to their high costs and

aesthetically unacceptable view. Also, multi joint cooling/heating systems are appropriate for small to medium

residential and commercial applications. However, in this cooling/ heating technology each evaporator (indoor

unit) has its own set of refrigerant pipework connecting it to the condenser (outdoor unit). This technique is

seen to be very similar to the VRF system but the main difference is that multi joint systems are unable to provide

individual control over different independent thermal zones. Also the user cannot utilize cooling and heating for

different zones at the same time. Either cooling or heating should be used in this technology. In our project,

which consists of 6 different zones or rooms to be conditioned, multi joint cooling systems can be a good choice

in regards with their low visual impact and spatial need. The only issue here seems to be the very long refrigerant

piping system that comes from the outdoor unit to every indoor unit and makes the multi joint technology less

desirable [60], [61]. Figure 14 shows the multi joint cooling/heating system.

FIGURE 14 SHOWS MULTI JOINT COOLING SYSTEM [61]

27

Fan coil cooling systems

Fan coil systems, which are categorized under waterborne, hydronic or all water systems, are used in many

different type of buildings for several decades worldwide and became a popular cooling, heating and ventilation

technology. The basic components of a fan coil unit are heating/cooling coil, fan section, and a filter. The system

is flexible enough to work alone in one zone or to be connected by ducting system to serve multiple zones. Fan

coil systems can be controlled by a manual switch, thermostat, or more complicated and sophisticated building

management systems. It is very interesting to know that Building Control System or Building Energy

Management System can easily manage and control the fan coil units regardless of their configuration and size.

Furthermore, the main energy carrier in this technology is water which is heated by a boiler or cooled by a chiller

in a central plant and sent to the units inside the house or building. Also, in cold climates in order to prevent

freezing of the water some chemical treatment is often involved and conducted in water. This includes the

addition of propylene, ethanol or ethylene glycol to water. However, these additives alter the heat transfer

properties of the fluid and designers should be aware of this issue before adding them to the system [62], [63].

Fan coils typically utilize a two or four pipes configuration. While two pipe systems cannot use both heating and

cooling at the same time for different zones, four pipes systems have the ability to use both cooling and heating

simultaneously. Although, two pipe systems have lower initial costs and installation process is easier and less

time consumer, they are not flexible with cooling and heating demand since changing from one to another for

the entire system is a time-consuming process. In other words, some issues can arise such as when seasonal or

occupancy loads change for starters. Obviously, four pipe systems have higher piping and installation costs but

occupant comfort and IAQ can be kept at an acceptable level in all seasons and conditions. Figure 15 and Figure

16 show the two and four pipes fan coil configuration in detail [62].

FIGURE 15 SHOWS TWO PIPE FAN COIL UNIT SYSTEM [62]

28

FIGURE 16 FOUR PIPES FAN COIL UNIT SYSTEM [62]

As it comes from the name of this system, fan coils always have a fan to blow air across a chilled or heated water

coil, which in turn is supplied to the zone or room. The supply air can be a mixture of outside and inside air with

specific percentage or just a recirculation of the inside air [62], [63].

Another aspect of the fan coil systems is the capability to remove the undesired humidity inside the envelope in

hot and humid climates. As the warmer and moist air passes through the cooling coil which has a temperature

below the dew point temperature of the ambient air, condensation occurs on the surface of the coil

immediately. This can create serious issues with regards to water leakage under or around the indoor units if

the unit is not installed correctly. Auxiliary condensed water pipes that lead the condensed water from indoor

unit to the outside of the building are very important and must be correctly installed. To our knowledge, while

the average relative humidity level in Accra is between 70 to 85% throughout the year, dehumidification

measures should be taken into account during the designing of the cooling systems.

Figure 17 demonstrates the various coil unit configurations that can be installed in different places of the

building depending on the zone requirements. While some of them can be installed under ceiling (horizontal fan

coils), others are directly installed on floor (vertical fan coil units) [63].

FIGURE 17 SHOWS DIFFERENT INDOOR FAN COIL UNIT CONFIGURATIONS [63]

29

Radiant Cooling Panels

This technology is very similar to radiant heating systems but in reverse. The thermal energy is exchanged

between the cooling panels and heat loads present in the zones or rooms. Even though there is no forced

ventilation to facilitate cooling, a uniform cooling gradient in the room can be achieved. Thus the risk of a draft

is naturally avoided by means of this technology [64].

It is recognized that the dominant cooling mode of the ceiling radiant cooling panels are long wave radiation

heat transfer. Several attempts have been made in order to obtain the indoor non-steady state radiation heat

transfer model of radiant ceiling cooling. A paper written by Zhang et al. [36] is a good example of them.

According to Ning et al. [65] radiant cooling panels have the potential of energy savings, good indoor

environment provision and improved thermal comfort. They found that radiant cooling panels, which are

modified with thin air layer, not only can provide a uniform surface temperature distribution but also may

control the condensation issue in hot and humid climates. This is mainly in contrast with finding of other survey

conducted by Hu et al. [66] in hot and humid areas of China. They clearly showed that condensation is one of

the problems that limits the application of radiant cooling in hot and humid areas. According to Tang et al. [67]

the condensation rate on the radiant ceiling was 25% greater than that on the radiant wall and 3.5 times greater

than that on the radiant floor. One of the most effective measures that can be suggested to overcome this crucial

issue is by increasing the chilled water temperature to prevent condensation. However, by this, the cooling

capacity is decreased with the increase in chilled water temperature which is not desirable and may lead to

decreasing thermal comfort and increase the percentage of PPD which is not acceptable. Another solution to

the condensation issue is to utilize a parallel installed ventilation or small air handling unit (AHU) which is capable

of dehumidifying the entering fresh air and recirculating the room air at the same time. Also, the entering chilled

water temperature to the panel is generally between 14 °C and 16 °C. Figure 18 shows the radiant cooling panel

and its infrared image.

FIGURE 18 SHOWS RADIANT CEILING COOLING PANEL AND ITS INFRARED IMAGE [65]

As a summary, we add the advantages of the radiative cooling panel systems as below;

It decreases the mechanical cooling load and operational costs while the cooled ceiling panels operate at

relatively high temperatures like 16 °C. It also works under silent and draft free conditions in contrast to

conventional air conditioning systems like split AC or VRF systems. Finally, it possesses smaller spatial

requirements in comparison to ducted HVAC systems. Figure 18 and Figure 19 demonstrates the temperature

variation acquired by CFD simulation on a standard cooling panel.

30

FIGURE 19 SHOWS TEMPERATURE VARIATION ON SURFACE OF A STANDARD COOLING PANEL [65]

Air Handling Units and Ventilation Systems

One of the crucial and essential components when dealing with house design and thermal comfort is ventilation.

As already mentioned before in the thermal comfort part, the need for having ventilation is mainly due to

accumulation of undesired pollutants derived from occupants’ activities inside the building which consequently

need an introduction of a reasonable amount of fresh air and removal of aged air from the building. While with

regards to ASHRAE Standard 62, the minimum fresh air ventilation per person for any type of building is 8 l/s

which is able to dilute the CO2 concentration inside the envelope and maintain it around 700 ppm, the Swedish

BBR standard has a slightly different definition for ventilation rate. According to this standard, the minimum

ventilation rate for a building is 0.35 l/s.m2 of living area. To get the desirable and acceptable indoor climate

proper ventilation units should be installed correctly to introduce the fresh air and reject the exhausted aged air

that has accumulated inside the house [47], [51].

Besides, all buildings are in need of temperature control to acquire an acceptable indoor climate. Air handling

units or AHU is another complicated system equipped with cooling and/or heating coils and air filters that are

dedicated to cover the cooling, heating, humidification and dehumidification demands for the different zones in

buildings. AHUs can easily process the outside air before it reaches the indoor area according to the demand.

For hot and humid climates like Accra, there will be no need to turn on the heating coil since the outdoor

temperature never drops under 23 °C around the year Figure 40. In contrast, the cooling coil should constantly

operate to diminish the humidity content and reject unnecessary amount of water vapor and heat entering with

the fresh air. According to ASHRAE standard maintaining the relative humidity in hot and humid climates to

around 50% is desirable and more convenient [47]. However, the initial costs and high energy consumption of

AHUs can be a reason to avoid using them in small residential buildings like our project with only 140 m2. Thus

the utilization of private ventilation (PV) and small scale supply and exhaust ventilation systems with heat/cold

recovery (FTX) units can be seen as an alternative to huge and costly AHU systems. Figure 20 shows the

schematic of a AHU and PV system which are working together to provide a better indoor climate for occupants

in an office building in a hot and humid area [68].

31

FIGURE 20 SHOWS AHU AND PV SYSTEMS WORKING TOGETHER IN A HOT AND HUMID ARE [68]

However, another important factor of infiltration should be taken into consideration when dealing with

ventilation rates and fresh air requirement. To our knowledge houses with an average and bad insulation have

higher infiltration air change per hour (ACH) than in tight and well-insulated houses. In the following parts of the

report we will show how variations in ACH can change the indoor climate radically in terms of CO2 accumulation

and amount of the fresh air.

Exhaust and supply air ventilation with heat recovery (FTX system)

This energy efficient system performs well regardless of the weather and can supply large amounts of fresh

ventilation air to the different zones of a building. There are two fans one for exhaust and one for supply air. If

the FTX system is designed for heat recovery the entire process can be expressed as below. The exhaust air is

drawn from the utility room, kitchen and bathroom, which have higher temperatures and the supply air is sent

to bedrooms, living rooms and the studio in the central unit of the FTX. There is a heat exchanger in which the

warm exhaust air energy is transferred to outdoor. The whole process can save a heating energy of 50 to 60% in

comparison with ventilation systems without heat recovery unit. The only thing is the maintenance of the unit

in even intervals of 1 year to change the dust and pollutant filters and clean the diffusers from unwanted

accumulations of dust and other substances [69], [70].

However, in the very cold days of the year, the heating energy passed from exhausted indoor air to fresh outdoor

cold air may not be sufficient to get the desirable temperature before introducing the ventilated air to the zones.

Thus, there is a need for a heating coil to process the supply ventilated air temperature and rise it to the desired

set point. Also, there will be some interruptions during the very cold days which is due to defrosting of the FTX

coils for some minutes per hour [70].

Humidity Control of the Fresh Air in Hot and humid Climates

In contrast with the heat recovery FTX system which is equipped with heating coil or electric heater, the FTX

units planned installation in hot and humid climates should be equipped with a cooling coil to reduce the

32

temperature and humidity of the supplied ventilated air [71]. Obviously, the efficiency of the cold recovery FTX

unit will be lower than the efficiency of the heat recovery FTX units due to the high temperature of the exhaust

air entering the heat/cold exchanger. However, the main reason to utilize this technology can be to provide

acceptable amount of fresh air to the zones, and reduce the CO2 levels inside the occupied rooms by dispatching

the aged and exhausted air from them. Also, the cooling coil of the FTX system can be connected to the chiller

unit of the fan coil system or outdoor unit of the VRF air conditioning system which is situated outside of the

house [34].

According to psychrometric data, dew point will be higher if the temperature and humidity are both high. At

surface temperatures below those dew points, the risk of condensation and water damage is too high. Therefore,

having a cooling coil in connection with FTX ventilation is crucial and a must have factor. Figure 21 show the

different dew points for different temperatures and humidity ratios.

FIGURE 21 SHOWS RELATIONSHIP BETWEEN DIFFERENT DEW POINTS, TEMPERATURE AND RELATIVE HUMIDITY AT 1 BAR

ATMOSPHERIC PRESSURE [72]

Figure 22 demonstrates the schematic of the cooling coil unit of the AHU system installed in hot and humid area

[71] while Figure 23 shows a heat recovery FTX ventilation system which is used very commonly in Sweden [70].

The illustration shows a FTX system with following components and functions. No 1. Fresh outdoor air is

introduced, supply air. No 2. The cold supply air is heated in a heat exchanger using the extracted warm room

air, exhaust air. No 3. The heated supply air is distributed in the house. No 4. The polluted exhaust air is extracted

from the kitchen and bathroom. No 5. The exhaust air gives up its heat to supply air in the heat exchanger and

flows out.

33

FIGURE 22 SHOWS AN HEAT/COOL RECOVERY AIR-HANDLING UNIT SYSTEM [71]

FIGURE 23 SHOWS THE OVERVIEW OF A FTX SYSTEM [70]

34

Smart Home Technologies

Smart home means that the home systems have an ability of self-regulation to the preferred environment

condition, and can be locally and remotely controlled and monitored [10], [73]. According to the smart home

reviewed by L. Jiang at el. [73], a smart home usually consists of an internal network, system gateway and smart

products. The internal network present in the market are Powerline, Busline and Radio Frequency (mainly used

in the smart home industry). It is used to connect the devices and gateway. The system gateway is the brain of

the system that control and set the logic behind it. This can be called smart hub. The Figure 24 shows the smart

home concept which the blue and orange arrow shows the sending and receiving communication while the dash

line represent the indirect connection between the apparatus. However, the illustration is not included the other

appliances like television, washing machine etc.

FIGURE 24 SHOWS THE SMART HOME CONCEPT APPLIED TO THE PROJECT

The nowadays technologies of smart hub can connect to the internet by wired network or wireless signal. The

last thing is smart devices that can be controlled by obtaining the command from the smart hub. Smart devices

for smart homes are increasingly used in home automation. Many manufacturers have been producing smart

35

home appliances that can connect to the smart hub or connect to a wireless router. At the end of the day, the

smart home system will be exploited in a significant number of field such as energy saving, security and

healthcare to promote the best living quality.

Lighting Automation & Daylighting utilization

Lighting electricity consumption by US residential buildings was counted as 14% in 2014 [74]. Electricity waste

reduction is the very first strategy to be considered [23], and one way of achieving that is to install a occupancy

sensor. The occupancy sensor is a technology that force the lighting system to turn on/off or dim according to

the availability of the occupancy. Occupancy sensors with different lighting control systems have been

investigated in [75], since it is the most successful strategy for energy saving from lighting. The systems were

tested in the private office building. The result shows that without the dimming system, the occupancy detector

saved energy by 20 to 26% [75]. The automatic light dimming control is found to be the most efficient system

for energy saving compared to Manual Dimming and Bi-level switching [75].

A research by Mohammad Asif Ul Hag [76] has done a review on lighting technologies. It states that to choose

the right technologies, users' behavior need to be surveyed due to the effected factors such as the occupancy

sensor time-delay setting. Similarly, choosing dimming or switching or open and close loop can be influential

when having a daylight-linked system. The research suggested that the schedule lighting control is widely used

due to the ease of implementation and lower cost, and it satisfies users more than the others due to the

consistency of the system [76].

LED light bulb

From market research, light-emitting diode (LED) light bulbs used in most of houses are 60 W equivalent;

however, it consumes only 10 W of electricity. But the price is relatively high compared traditional tungsten light

bulbs. On the other hand, it can give environmental advantages in the long run and possibly be beneficial from

an economical point of view. Figure 25 shows the smart LED hub and light bulbs that is available in the

commercial market.

FIGURE 25 SHOWS THE EXAMPLE OF CONNECTED LIGHT BULB [77]

Occupancy sensor

Different occupancy sensors are used in the market such as Passive Infrared (PIR), Microwave, Acoustic and

Ultrasonic. However, these technologies still have falsification; for example, the light is turned on when there is

no actual movement of occupancy and the light is turned off when there are occupants present in the room [76].

Figure 26 shows the wall and roof occupancy sensors that are used in the commercial market.

36

FIGURE 26 SHOWS WALL AND ROOF OCCUPANCY SENSOR [78]

The most widely used sensor in the market are Passive infrared (PIR) and Ultrasonic. Radio Frequency

Identification (RFID) and digital imaging are under development [76].

Passive infrared (PIR) sensor

PIR is a type of sensor that detects change of temperature by using a sensor called Pyroelectric detector.

Distance is an important factor that leads to high or low accuracy. The issue of PIR is ‘False-off’ errors which

mean that it turns off the lighting system despite having occupants in the space due to a gap in the sensing zone.

The sensing zone gap increases according to the distance [76].

Ultrasonic sensors

The principal of Ultrasonic sensors is to emit ultrasonic sound to detect difference in the duration between back

and forth movement called Doppler Effect. This gives an advantage over PIR since vision is not required for this

type of sensor. However, Ultrasonic sensors, sometimes, make ‘False-on’ errors since it is sensitive to any

movement even though they may not be from the real occupants. Moreover, one disadvantage of ultrasonic

sensors which is similar to PIR is that the accuracy goes down when the distance increases [76].

Radio Frequency Identification (RFID)

RFID has been mainly used for personal identification. However, some research used RFID to increase the

accuracy and remove the errors in the existing PIR sensors. A researcher developed a RFID gateway to record

the density and profile of the occupants. However, passive RFID has lower accuracy. Low accuracy can be solved

by using an active RFID, but it can be manipulated by obstacles. A researcher, Zhen et al, has purposed multiple

readers which can decrease the errors of active RFID [76].

Digital image

Due to the already mentioned falsification of the technologies, researchers purpose a new method using digital

imaging to detect occupants. The method uses cameras to detect occupants. The basic principle of the sensor is

to apply machine learning on imagery. One research investigated the availability of humans by detecting the

human head, and found out that the system proved to be accurate. [76].

Control classification

Electrical and Daylighting control

As already mentioned, the method of daylight control is divided into two categories: switching and dimming

[79]. Both controls are according to the daylight level. Some research has investigated the multiple-level

switching control, which considers daylight availability and the function of the sensing zone. The system of

daylighting control is divided into two types: closed and open loop. In a general explanation, a closed loop system

detects both the daylight level and artificial light and sends the signal to the switching or dimming control. On

the other hand, an open loop detects only the daylight level and sends the signal to the control system [76].

37

Lighting schedule

The lighting schedule system is to set the exact time when the lighting system should be on or off. The system

works well in a room where the schedule of occupancy is fixed or certain, such as classrooms or the outdoor

spaces. The system can save energy significantly if it is used in the right place [76].

Switch control strategies

The switching control is divided into three strategies as follows.

Light switching technology

It is important for the delay setting to have the right values in the place where the occupant get in and out quite

often since the occupants are not satisfied when the room is completely dark after coming back. The control

gives a high saving when it is installed in the appropriate place [76].

Light dimming technology

These technologies can tackle the problem of the switching technology since this technology can dim the light

down when it detects no occupants presents in the space. Therefore, this better satisfies users when the

schedule is short and often occupied. It is suitable for places with varying sunlight [76].

Mixed system

The combination between occupancy sensor, passive daylight and lighting schedule can be used at the same

place together or separately in the same building, but in different rooms to optimize the energy consumption.

At the end of the day, in order to know which technologies and system have the best match, the users' behavior

should be surveyed. Applying occupancy sensor with daylighting, 46 to 68% of savings are shown in the research

[75], [80], [81] [76] and 38 to 61% of savings from lighting schedule and daylighting [82].

The system function and other affected factors

The research by Andrea Peruffo [83] investigated the central wireless lighting control system, occupancy sensor

and different daylight by using Zigbee wireless network. The research mentioned that central lighting control

are more flexible in specification than distributed lighting controls, and wireless lighting systems give more

advantages over wire systems since it is easier to retrofit, but would be affected by delayed issue. By improving

the control law and transmission redundancy, the wireless network can perform as well as the wired system

[83].

Daylighting

A research by Marc Fontoynont [84] investigated the economic feasibility of natural daylight and electric lighting

in office building. The research did a comparison of different scenarios related to the increase in ceiling height

and applied with the different shapes of light wells. It was found that the light wells work properly when the

distance to width ratio is up to 5. The research concludes that long light wells perpendicular to the façade are

the most proper way to increase exploitation of the daylighting [84].

A research by Zain-Ahmed et al. has investigated passive solar design in office buildings for exploitation of

daylighting with the effect of cooling demand. The research varied windows to wall area (WWR) with the chosen

standard of lighting criteria as 500 lux. It found out that the heat gains from artificial light decreased when the

WWR increases from 10 to 25%, but increased when the WWR more than 30% simulated in February in Malaysia.

However, this problem can be tackled by using a shading device, which will be discussed in another section [85].

A research has studied the interaction of light and heat from harvesting daylight. It is found out that the skylights

are not appropriate for direct application in hot climate countries like Malaysia due to the balance between

cooling and lighting loads, but can be integrated with other systems such as shading, prism, etc [86].

38

A research by Sung Jin Oh[87] has studied daylighting from two technologies: sun tube and fiber-optic solar

concentrator. The research was done using Photopia and Radiance software for simulation of light tube and

daylight simulation in the building. The study concludes that dish concentrator system is appropriate when the

solar altitude angle is higher than 50 [88].

General daylight technologies and designs have been defined in [89]. There are four common ways to exploit

daylight: daylight from windows, light tubes, light shelves and Heliostats. This section will review the current

technologies and basic principle of the technologies.

Windows & glazing

One important part of residential houses is windows where heat gain and daylighting gain need to be optimized.

The windows industry has developed selective windows to screen out infrared, but allow visible light to pass

through. The way to reduce solar energy transmittance, but keep visible light is to coat the single or double

layered glass with silver. The arrangement of different coating layers is done differently depending on climate

application [89]. However, there is another technology called “Switchable grazing” or smart windows. The

windows can self-adapt according to the weather condition [89] which solves both the heat gain and daylighting

issues, but are still too expensive.

Tubular light

Light tube is a technology that gathers the light through the pipe and diffuses it in the functional space. The

diameter of the tube and reflective performance of the inner tube coating are important for light tube

performance. The larger the tube is, the higher the performance since it decreases the number of bouncing,

which reduces the light at the destination. The light tube is useful when the light is needed to be brought into a

deep area inside the house where sunlight from windows cannot access [89]. Figure 27 shows the components

of light tube commonly used.

FIGURE 27 SHOWS THE CONCEPT OF TUBULAR LIGHT [90]

39

Light shelves

Light shelves, shown in Figure 28, are a design for daylighting maximization. It is usually designed into two layers

of windows to block sunlight from coming directly into the viewing window, which can cause glares and leads to

discomfort for occupants, and to redirect the sunlight to diffuse at the ceiling. However, the design leads to

higher ceiling to have another window layer, which causes the increase of cooling demand.

FIGURE 28 SHOWS THE CONCEPT OF DESIGNING LIGHT SHELVE [91]

Heliostats

Heliostats is a sunlight harvesting technology that tracks the sun's location and, concentrate and leads the light

through fiber optics. However, the technology is quite complicated, and a mechanical system is needed which

leads to higher maintenance cost. Therefore, the technology has not been widely used in the market [89].

Combination of daylighting exploitation and occupancy sensor

Energy saving on daylighting exploitation can vary widely since there are many different factors related to the

system, which would be difficult to simulate in a computer program. A research by Krarti et al. [92] has

performed the research accurately by using a simulation method compared to actual measurements, taken from

the building data such as building geometry and windows type .

Different control systems were investigated in different location in Europe using DAYSIM simulation software.

The research recommends two steps of lighting simulation: daylight simulation and electric lighting simulation.

Radiance has been used for daylight simulation [93]. To be efficient in using daylight and lighting system, the

software can be optimized by using a lighting control system. Another research said that Occupancy sensor can

save up to 84% when combined with daylighting system [76]. The research concluded that switching lighting

control is more preferable in small office, at the same time, dimming is more preferable for large offices. It also

recommends that the rate of savings from occupancy sensors increases when the rate of occupation decreases.

The factors effecting the daylight exploitation are daylight availability, chosen control and the control

parameters. Weather conditions, types of windows and obstructions can be taken into account for daylight

exploitation. Dimming or switching and closed loop or open loop have to be chosen properly to have the best

40

performance according to the user’s behavior. The important control parameters are the level of lux, time delay

setting and sensor location which need to be considered together with the type of the chosen system [76].

Smart Thermostat

For cooling or heating systems, the thermostat controller or remote control is needed to switch cooling systems

and adjust the preferable temperature. In some places, the heating or cooling is left on for supplying preferable

thermal comfort at all times. In some places, the system start working on demand after the users arrive at the

place. However, both of the controls have their own advantages and disadvantages. Leaving the system on can

consume significant amount of energy and lead to higher expenses, but provide satisfying thermal comfort.

Being on demand can result in poor thermal comfort. Smart thermostat has been developed with one reason

for solving the problems. Several principles of smart thermostat are the ability to learn the user’s behavior, to

know user’s schedules and preferences, to detect indoor and outdoor climate condition to optimize the fan

speed and compressor of cooling and heating systems [94]. An example of smart thermostat is the Nest

thermostat developed by Google. The device can learn the user’s behavior by manual adjustment and occupancy

sensors for setting the schedule. The device can also learn the preference set point for turning it on before the

occupied period and to make sure the cooling system is off when there is no occupant. According to the Nest

smart thermostat, it reduces cooling waste due to over cooling supply by stopping the cooling system before it

reaches the set point and utilizes the cooling left in the coil for about ten to fifteen minutes [94]. It can

significantly benefit a central cooling or heating system that has a big cooling or heating cycle. By knowing the

schedule in advance, the optimal set point can be reached at the leaving or arriving time, and optimized in

different way to give the best thermal comfort. Energy efficiency can be achieved by investigating the best

weight in different stages of set points [94]. Another device by [95], can be controlled according to the location

of the users for optimizing the energy consumption and the thermal comfort. A research by [96] found out that

by having HVAC control 2.0 function, the cooling demand decreases by 5.4% for multi-stage cooling system. An

energy research by different smart thermostat manufacturer shows significant energy reductions of 14% to 31%

[97], [98], [95] compared to the constant temperature setting. The research used constant temperature because

of the ease and clarity when comparing, as well as, the programmable thermostat does not work as it claims

[99]. However, Nest investigated the energy reduction from smart thermostat when a real condition is applied.

The method is used with the statistical techniques to compare the energy consumption of the houses before

and after using the thermostat. The result shows 17.5% of HVAC energy reduction [97]. Not only does the

thermostat help to reduce energy consumption, it also helps the house owner by eliminating the necessity of

installing overly large capacity air conditioner since it does not have to cool down or heat the house immediately.

In the commercial market, the smart thermostat or controller is divided into two types. First is the wired

thermostat, shown in Figure 29, which can only work with the cooling or heating system that is connected to a

thermostat via wires. Another is the smart, Figure 30, controller that can control cooling or heating system via

infrared signal.

41

FIGURE 29 SHOWS THE NEST SMART THERMOSTAT [94]

FIGURE 30 SHOWS THE TADO SMART AIR CONDITIONER CONTROL [100]

42

Shading Automation

A research investigated exterior shading in office building to control solar load in two locations in California using

Radiance, Energy Plus and Windows 7 to simulate cooling and heating demands, lighting energy demand and

glare[101]. Twelve exterior shadings were investigated aiming to evaluate energy reduction from different

external shading, to measure the performance of computer simulation and to see the relationship of the external

shading to window to wall ratios. It concludes that moderate windows to wall ratio with exterior shading can

decrease cooling load, and automation shading can lead to a better energy efficiency due to the lighting and

cooling optimization. It also recommends that the future work might consider some shadings with clear view for

occupants [101]. The two exterior shading types that give a potential of both cooling reduction and daylighting

utilization are shown in Figure 31 and Figure 32.

FIGURE 31 SHOWS AN EXTERIOR VENETIAN BLIND [102]

FIGURE 32 SHOWS A WINDOW AWNING [102]

In a general understanding, external shading has more potential to reduce cooling demand since the heat is

stopped before penetrating into the building. However, some research argues that there are some other

advantages of internal shading such as lower cost, ease of repair, and flexibility of façade design. A research by

Yungyang et al. [103] has investigated the performance of high reflective internal shading through experiments

43

in Shanghai(China), which was verified by the experimental result using Energy Plus software. It is concluded

that if the internal shading was designed properly, it can give similar or higher results than external shading.

A research conducted experiments on sustainable house design and passive cooling in Abu Dhabi. One of the

strategies considered in the research is wall, roof and windows shading. It mentioned that the heat gains through

walls, roof and windows are slightly higher than 20%. It also said that by installing windows shading, the room

temperature decreased by 3 C, in the meanwhile, 2 C by walls and roof [104]. Another research done by Taleb

[37] did simulations on passive cooling strategies. One strategy was used louver shading devices by simulation

in Sun cast analysis. By applying all the passive cooling strategy, cooling load decreased by 9% and 23.6% for

annual energy consumption.

Shading devices are mainly categorized into three types: exterior, between and interior. The main function of

the shading device is to reduce cooling load and glare. The external shading device seems to be more effective

than the internal shading device since the heat already leaks in when internal shading is used. There are different

types of shading designs in the market: standard horizontal overhang, vertical louvers or fins, drop the edge,

slop it down, substitute louvers, louvers in place of solid overhang, and break up overhang. There is a suggestion

given by the literature to consider which type of shading should be used. The suggestions for specific location

are shown as follows. The literature recommends installing horizontal shading on the south and north sides, and

vertical shading on the west and east sides. Also, fixed and movable shading have to be chosen depending on

the budget [105].

The article on sun control and shading devices recommend how to design shading systems. The article suggests

using fixed shading on the South for the United States, and limiting the windows space on the East and West.

North roof shading should be considered for tropical regions. The light shelves should be considered since it

blocks the sunlight from lower windows but give daylighting on the top windows. There are adjustable shadings

mentioned such as canvas, roll-down blinds, shutters and vertical louvers [106].

The balance of the benefit from daylight and energy demand reduction was investigated in the private office

[107]. It shows an interesting result that by applying shading automation, 30% to 50% of windows to wall gives

lowest energy consumption for most of the cases. Moreover, shading automation shows potential of increasing

availability of daylight [108].

Door Sensors

The energy demand in residences in hot climate countries is mainly from cooling demand. According to heat

transfer principles, heat can transfer by conduction, convection and radiation. When these principles are applied

in buildings, one can say that the heat gain in the buildings occurs from conduction and radiation through

building envelopes. In the meanwhile, convection can occur through holes or suboptimal sealing envelopes or

from openings in walls or windows, and the ventilation system. These problems can be solved by an effective

heat exchanger installation. We have discussed selection of building insulation and windows in the earlier

section. In this part, the solution for infiltration reduction from door control will be discussed, and the infiltration

from building envelope will be discussed in the Effect of Simulation Factors section. The example of door sensors

is shown in Figure 33.

44

FIGURE 33 SHOWS A MULTI-PURPOSE SENSOR [109]

Building infiltration from doors

Leaving the doors and windows open can increase the infiltration rate significantly. However, it is difficult to find

the value or to research the increase of infiltration due to leaving doors or windows since the result can be highly

dependent on the user’s behavior and the cooling/heating systems. According to personal experience, the error

of the building energy simulation varies significantly as a result of the users leaving windows and doors open

unintentionally. Since, it is difficult to estimate the windows opening pattern, only the inside door is taken into

account since it is always left open even though the air conditioner is on. This leads to higher energy

consumption since it has to cool down the other parts of the house without occupancy.

A home design guideline by the Australian government suggested that aside from sealing the air leaks of the

gaps in envelopes, doors and windows need to be taken into account for infiltration reduction. It is

recommended that all external openings should be installed with an airlock, and also that cavity sliding doors

should be avoided due to difficulty in sealing. Another common way to improve air-tightness is to install

automatic door closers [110].

The Effects of Simulation Factors

Occupancy profile

The different measures of energy saving combined with occupancy pattern modelling were investigated by

Marshall et al. [111]. Four strategies and three types of occupancy patterns were applied. The research shows

the significance of suitability between energy efficiency actions and occupancy patterns.

The residential occupancy pattern in the developing country Kuwaiti, was shown and investigated in detail. The

30 households were surveyed by entering the data to the simulation software, ENERWIN. The occupancy,

lighting and appliances were created. By replacing the default values with measured data and increasing

thermostat setting from 22 C to 24 C, the result of electricity consumption increase by 21% [112].

The influence on occupant behavior for power management has been investigated in [113]. Brahms

environmental model was used in the research showing the number of occupants present in the house during

different times of the day. However, the research does not show the schedule of the users occupying each room

during the day.

45

Another research investigated the impact of human behavior and different factors such as family size, heating

system, insulation level etc. TAS software was used for analysis and energy simulation. The temperature

characteristic combined with occupancy profile showed how many people occupied different rooms for each

time. The result shows the relationship between occupants’ lifestyle and insulation level [114].

Sealing building envelope

There are a lot of guidance on where and how to increase building air-tightness. The value can be obtained from

experiment, which is not in the scope of this research. The rough value of the increase in air changed value

signified air tightness due to envelope sealing can be found in different literatures.

A research by Wei Pan explored the air-tightness value in 287 new buildings after 2006 in the UK, and also

investigated the relationship between air-tightness and different factors. The average value of air-tightness in

the UK was around 5.97 m3/hm2 at 50 Pa. The result shows a difference from previous research, which is higher.

However, the air-tightness value of the buildings in the UK are still higher than buildings in Canada and

Scandinavia [115].

An office building using rammed-earth construction was compared in simulation for investigating energy

consumption. The research found that the rammed-earth building required higher heating demand than another

office building in the same location due to higher infiltration rate[17].

The effect of air-tightness to energy performance was investigated in [116]. The sample was done in 27 single-

family houses. The value of air-tightness in class A buildings was found to be 0.6. In the meanwhile, ACH50 of

building B and C were 4.17 to 8.05 at the confidence level of 90%. The value of ACH50 of building class A, B and

C were presented in the paper.

46

Asaduru Sustainable House Project

The project is conducted on the house designed by Asaduru company which is intended to be a model of

sustainable community in Accra, Ghana. The project will be located in Accra as shows in Figure 34 with twenty

houses and central facilities such as a swimming pool and a fitness as shown in Figure 35. There are three

different house models in different orientations, which consists of two, three and four bedrooms. All the models

have a kitchen, living room and bathrooms in common. Figure 36 and Figure 37 show the 3D model and house

plan respectively of a three-bedroom house in the project. The houses will be built by rammed-earth

construction method, which is considered to be an energy efficient way of construction, due to its high thermal

mass that can keep the inside of the house cold for a significant duration of time and the possibility of recycling

the building material after the lifespan of the houses. One of the house model is chosen to be tested in pursuit

of energy efficient implementation methods. The model that was chosen in this project is a three-bedroom

model with 138 m2 living area. The model house faces toward 30-degree North West direction. The house model

and plan are illustrated in Figure 35 and Figure 36 respectively.

.

FIGURE 34 SHOWS THE LOCATION OF THE PROJECT [18]

47

FIGURE 35 SHOWS THE OVERVIEW OF THE PROJECT [19]

FIGURE 36 SHOWS THE 3D HOUSE MODEL OF 3 BEDROOM PLAN [19]

48

FIGURE 37 SHOWS THE PLAN FOR THE 3 BEDROOMS MODEL HOUSE OF ASADURU COMPANY [19]

Rammed-earth construction technology

The rammed-earth construction method is a sustainable method of building construction which utilizes

compressing of earth layers successively in order to get the desired strength and shape for walls and floor. Soil,

sand and some other stabilizers like cement can be mixed and added together to form the appropriate mixture.

Figure 37 shows the example of an already built rammed earth building. This method is environmental friendly

from cradle to grave since it uses the local materials and can decrease the transportation related GHG emission

beside cutting down the initial investment costs. In addition, it can be demolished easily, after life span of the

building. The parts of the building which are made of rammed earth like walls and floor can be added to the

environment without creating any damage. Another advantage is that this technique can be used in areas with

lack of construction materials like rural areas [20]. Figure 39 illustrates the process of the making a wall in

rammed earth method step by step.

49

FIGURE 38 AN EXAMPLE OF RAMMED EARTH CONSTRUCTION [21]

FIGURE 39 THE PROCESS OF COMPRESSING EARTH IN RAMMED EARTH CONSTRUCTION METHOD [22]

Weather and climate data for Accra project

There are mainly two seasons in Accra, Ghana, which are the wet and dry hot seasons, since the region is located

close to the tropical line. The seasonal temperature varies slightly by about 4-5 degrees Celsius, and includes

day and night temperature variations. The maximum temperatures are 34 degrees Celsius from November to

April and around 28-32 degrees Celsius during the remaining months as shows in Figure 40 and Figure 41. May,

50

June, July, September and October have high precipitation compared to the other months as shows in the Figure

40. Due to Accra's location in the coastal area of Atlantic Ocean and its proximity to the tropical line, the

maximum humidity is mostly higher than 80% as shows in Figure 43. According to the monthly sun hours, the

lowest sun hour months are from June to September, which possess around 150 hours while the rest of the

months possess more than 200 hours. The sun orientation is as shows in Figure 45. Wind speed was mostly less

than 28 km per hour (7.7 m/s) as shows in Figure 42. In addition, the dew point for Accra climate can be seen in

Figure 44.

FIGURE 40 SHOWS THE AVERAGE TEMPERATURE AND PRECIPITATION OF ACCRA GHANA [117]

FIGURE 41 SHOWS THE SEASONAL TEMPERATURE RANGE OF ACCRA GHANA[117]

51

FIGURE 42 SHOWS THE WIND SPEED OF ACCRA GHANA [117]

FIGURE 43 SHOWS RELATIVE HUMIDITY IN ACCRA GHANA [118]

52

FIGURE 44 SHOWS THE DEW POINT OF ACCRA GHANA [118]

FIGURE 45 SHOWS THE SOLAR IRRADIATION ON THE PROJECT [19]

Figure 45 shows the solar irradiation and its orientation during the whole year for the project in Accra Ghana.

Since the project is close to equatorial line, the sun is shining from the north east and is setting to the north west

in June and July while it is shining from the south east and setting to the south west in January and February. As

it is seen, solar orientation is located directly about the project during the year. The hexagonal shape in the

middle of the picture shows the Asadurus sustainable house project in Accra and the green lines are

demonstrating the inner roads and ways in the project. Houses are connected by these green lines and every

cluster of house has 4 house with different orientation and size.

53

Building design concept and strategies

A significant number of methods and tools for building design concepts and strategies has been reviewed in the

Andresen et al. [23]. One well-known and easy to understand method is the Kyoto Pyramid which is based on

the Energetica method and explained by Lysen 1996. The method was developed by SINTEF Byggforsk and the

Norwegian State. The strategy consists of five steps of building design concepts to achieve the highest energy

efficiency. The five steps are as follows and are illustrated in Figure 46:

1. Reduce heat or energy loss: Insulation, tight envelope and double or triple panes windows

2. Reduce electricity consumption: utilization of high efficiency light bulbs and appliances

3. Exploit solar energy: exploitation of solar hot water, and solar cells

4. Control and display of energy consumption: smart home, home automation, effect of energy

monitoring

5. Select energy source and carrier: like biomass, wind etc.

FIGURE 46 SHOWS THE OVERVIEW OF KYOTO PYRAMID [23]

Energy demand in residential building in Ghana

Ghana has a relatively low GHG emission, especially for CO2 emission per capita in comparison with other

developing and developed countries [24]. However, its current situation does not give the country room for

negligence in development planning. Right decisions in constructing more efficient houses are essential for the

future of the country since there is high potential for new buildings in Africa [5] it would be a good idea to start

building of sustainable communities in Africa [24].

54

Energy efficient house design and its characteristics

In order to clarify the concept of an energy efficient house, the term is referred to the reduction of the amount

of energy required in a house with different occupants and systems. Some examples of the energy efficient

techniques and measures are better insulation, LED or fluorescent bulbs, skylight or daylight systems, radiative

and reflective roofs, green roofs, natural ventilation, better window glazing, indirect radiant cooling and

orientation of the house. [25] The following parts will discuss the different techniques in detail.

https://en.wikipedia.org/wiki/Fluorescent_lights

55

Modelling

Indoor Climate Energy (IDA-ICE)

IDA Indoor Climate Energy (IDA-ICE) 4.7 by EQUA with student license was used during the research for energy

simulation of the rammed-earth building. The software helps users to simulate and optimize energy

consumption in the building while providing the best comfort for the building's inhabitants, the software also

models the building's energy consumption by using energy and heat balance equations following the dynamic

time step. IDA-ICE requires an enormous mass of information such as weather data, building construction,

specifications site location, HVAC system specifications and the control settings. There are two types of models

in IDA-ICE; one with the full model which is simulated by full Stefan-Boltzmann radiation, the other is the

simplification of the radiation exchange of the room surface [15]. IDA-ICE can illustrate a significant number of

useful results from the building such as cooling and heating demand, electricity consumption from lighting and

appliances, the utilization of indoor daylight (Daylighting factor), ventilation and airflow direction, as well as,

shading of the building during the daytime. Moreover, users can set the controls of the equipment by

themselves, for example, the duration of the lighting utilization according to the user’s availability. The results

from this software can be useful for the building design.

Baseline modelling

General parameter

The building energy model was done by importing IFC file from other architecture software called Revit into

IDA-ICE software. Figure 47 shows the energy model of the three-bed room house.

FIGURE 47 SHOWS THE 3D ENERGY MODEL OF 3 BEDROOM HOUSE IMPORTED TO IDA-ICE [19]

The house model was provided by Asaduru and exported from the Revit software into an IFC file. The model

consists of eight rooms with eleven zones while the house model is single floored. The total area of the building

is 138 m2 with the roof area of 297.7 m2. The floor area zones and room height were illustrated in Table 1.

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TABLE 1 SHOWS THE ZONES GEOMETRY

Zone Room height m

Floor area m2

Studio 3.1 15

Living Room 4.2 29

Bedroom 1 3.1 14

Bedroom 2 3.1 12

Bedroom M. 3.1 20

Bathroom 1 3.1 8

Bathroom 2 3.1 7

Laundry 3.1 5

Corridor 3.1 10

Entrance 4.2 6

Kitchen 4.2 15

In the baseline model, all the parameters need to be set according to the real condition in Accra, Ghana as

accurately as possible. The weather condition was taken from Energy Plus website as EPW format. The location

of the houses was set according to the geographical coordinates. Wind profile was obtained from the default

setting which follows the ASHRAE 1993 for suburbs. The house orientation of the normal line of the front door

is directed toward the North-west without any shading from obstacles since the project is located in a suburban

area and each house is placed some distance from each other. All the thermal bridges are set to be typical as

the default value. The infiltration rate was set to be 0.5 ACH at a fixed rate which is high enough to maintain the

indoor CO2 level without a ventilation system according to the simulation, which represent the lifestyle

occupancy behavior in hot and humid climate. The common behavior of occupants in the region is to open the

windows since the ventilation system are not commonly present in residential buildings. However, wind driven

infiltration flow setting without ventilation causes the indoor CO2 level to increase to unacceptable levels.

Pressure coefficients are set to be Semi-exposed according to the IDA tutorial.

The house is divided into eleven zones with some rooms connected without any doors in between. However,

the software understands each zone to be a separated area without any connections, the desired model is

assumed contain a door in between the connected zones and is set to be always open, so the air between the

room can flow freely. Since the project will be built using rammed-earth construction, both inner and outer walls

are made of rammed-earth. Due to reasons of construction safety, thickness of the rammed-earth walls need to

be at least 30 cm. Therefore, the thickness of both inner and outer walls are 30 cm. By entering the thickness,

density, thermal conductivity and specific heat of the material, the U value can be calculated by IDA-ICE

software. The U-value is calculated as 2.493 W/(m2*K). The input properties of the material can be found in

Table 2.

TABLE 2 SHOWS THE RAMMED-EARTH PROPERTIES

Rammed-earth properties

Thermal conductivity 1.25 W/(m.K)

Density 1800 kg/m3

Specific heat 1000 J/(kg.K)

U-value 2.439 W/(m2.K)

The roof consists of internal and external roofs. The external roof is based on concrete joist roof that consists of

light insulation and concrete. The internal roof is coated on low weighted concrete with U-value of 2.385

57

W/(m2K). All the properties of the roofs, wall and floor are shown in Table 3. The floor thickness is 0.3 m in total.

The main materials of both internal and external floors are concrete and lightweight concrete.

TABLE 3 SHOWS U-VALUE AND THICKNESS OF BUILDING ENVELOP

Types U-value (W/(m2K) Thickness (m)

Wall 2.439 0.3

Roof 0.172 0.35

Floor 2.9 0.255

Due to the low price and low difference between the outdoor and indoor temperatures during a whole year in

Accra, the commonly installed windows are single glazed. As a result, the single pane windows were chosen in

the baseline. The total U-value of the glaze of the single pane windows is 5.8 W/(m2*K). The other properties

have been shown in Table 4. The size and number of the windows modified in the project are in Table 5.

TABLE 4 SHOWS THE GLAZING PROPERTIES

g (SHGC) Solar transmittance

Visible transmittance

Glazing U, W/(m2 K)

Frame fract., 0-1

Frame U, W/(m2 K)

Win total U, W/(m2 K)

0.85 0.83 0.9 5.8 0.1 2 5.42

TABLE 5 SHOWS THE WINDOWS SIZE AND QUANTITY

Window's size Quantity

1.22x1.22 5

1.83x1.22 4

0.92x0.92 1

4.66x2.22 1

Internal heat gain

The internal heat gain in the simulation is composited from three main sources; occupancy, equipment and

lighting.

Occupancy

The numbers of the occupants were set according to the function of the room and the possibility that the

occupants will occupy the room in order to cover the highest cooling demand. The schedule applied in the

simulation is a four-member family: one working, one wife housemate and two children without any summer

break.

Equipment

The equipment schedule and energy consumption are done in Microsoft excel using the energy consumption

data from the Sustainable Energy Utilization course at KTH [48]. Each equipment or appliance is chosen

according to the suitability for the room function, for example, the appliances chosen in the living room are a

radio, a TV and a video player were considered power peak of 40, 150 and 45 W respectively. The utilized

duration is in one-minute time intervals.

Lighting

Lighting is one of the internal heat gain sources. The 60W tungsten light bulbs were installed in the baseline. The

number of light bulbs was calculated based on the minimum illumination which is 150 lux[119]. The equation

used for calculating the number of light bulbs is based on Equation 2 for calculating total illumination. The light

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bulbs installed in the rooms are presented in Table 6. The lighting control connects to the occupancy schedule

and the availability of daylight mentioned earlier by setting the control macro of IDA-ICE.

EQUATION 2 FOR CALCULATING TOTAL ILLUMINATION [119]

𝐼 =𝐿𝑙𝐶𝑢𝐿𝐿𝐹

𝐴𝑙 (2)

Where

I - light output, lux

𝐿𝑙 - total illumination, lux

𝐶𝑢 - coefficient of utilization (0.9)

𝐿𝐿𝐹 - lighting loss factor (1)

𝐴𝑙 - area of utilization, m2.

TABLE 6 SHOWS THE ZONES AREA AND NUMBER OF LIGHT BULBS

Room Area (m2) Number of light bulbs

Studio1 15 4

Living Room1 29 6

Bedroom 1 14 2

Bedroom 2 12 2

Bedroom M. 20 3

Bathroom 1 8 2

Bathroom 2 7 1

Laundry1 5 1

Corridor 10 3

Entrance 6 2

Kitchen1 15 4

Cooling & HVAC system

In almost all conventional houses in Accra, Ghana, the middle to high-income population usually installed split

type ductless air-conditioning that needed separate outdoor units for each indoor unit. The ideal cooler in IDA-

ICE software is adapted in the baseline simulation for simplification. The type and capacity of the cooling system

for each individual zone to minimize the lowest dissatisfaction are shown in Table 7. It has to be noted that the

high percentage of dissatisfaction mainly comes from the zones where the cooling system is not installed and is

not needed such as bathrooms, laundry rooms, entrances and corridors. Although there may be some occupants

present in the zones, low temperature is not needed in the case. The control applied to the baseline is PI control,

which keeps the temperature constant at the local set points 23-25 °C for cooling. The coefficient of performance

(COP2) is set to be 3 with electricity consumption. Furthermore, due to high energy consumption and high initial

investments, AHU systems with the capability to process the outside air and introduce the clean air to indoor

areas are excluded in the baseline scenario.

TABLE 7 SHOWS THE COOLING CAPACITY IN THE BASELINE

Zones Type of cooling Cooling power, W

Studio © Ideal cooler 2500

Living Room © Ideal cooler 3400

Bedroom 1 © Ideal cooler 1000

Bedroom 2 © Ideal cooler 900

Bedroom M © Ideal cooler 1300

Kitchen © Ideal cooler 1850

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Energy Simulation of Technologies

In this section, the energy consumption was simulated to investigate and find the amount of electricity and

cooling demand that the technologies can reduce. At the same time, it is done to primarily find out how

economical and viable the technologies are to further simulation and evaluation of the energy consumption with

different scenarios when all the technologies are integrated as a whole system. Smart technologies include smart

LED lighting, smart thermostat, smart door sensors and shading automation. However, some of these

technologies cannot directly be applied to the software. In order to be simulated in the IDA-ICE, the principle of

these technologies was adapted and simulated to obtain an acceptable result.

Smart lighting, LED and daylighting

Smart lighting with occupancy sensors

The principle in this section is that the lighting can be assumed to be on and off according to the exact occupancy

schedule with the assistance of the occupancy sensor. In the baseline model, the occupancy schedule is set

according to the room function since the occupants would leave the lights on even though they are not present

in the rooms. This behavior leads to a waste of electricity that needs to be eliminated. In the simulation, the

lighting control was set according to the occupancy availability and the level of daylight, which was set to be 150

lux. When the representation of the new lighting utilization is desired, the occupancy schedule had to be

adapted. The new occupancy schedule was calculated hourly in the way that does not allow the total number of

occupancy in the house to exceed four people. However, by changing the occupancy schedule, the cooling

demand decreases with relation to the number of occupancy and lighting demand. In the reality, the lighting

demand decrease is due to the reduction of lighting consumption, but not due to the number of occupancy.

Therefore, the internal heat gains from the presence of occupants need to be put back to the cooling demand

of the new simulation. This is accomplished by simulating the new occupancy schedule with the baseline so that

it may be subtracted by the baseline simulation. The number obtained from the subtraction represents heat

gains from occupancy and lighting reduction. This number needs to be subtracted again by the lighting energy

reduction, which can be found by multiplying the lighting to cooling fraction with the energy reduction from

lighting. The equation for correction is shown in Equation 3.

EQUATION 3 FOR CORRECTION FACTOR FOR COOLING CONSUMPTION WHEN NEW SCHEDULE IS APPLIED

𝐶 = 𝑆 + [𝑇 − (𝐿 𝑥 𝐹𝑐)] (3)

C - Corrected cooling consumption, kWh/year

S - Simulated cooling consumption, kWh/year

T - Total cooling reduction from new schedule simulation, kWh/year

L - Lighting energy reduction, kWh/year

Fc - Lighting cooling factor, kWh/year

LED

The energy consumption from LED was simulated for both energy reductions from LED and energy reduction

from LED with occupancy sensors. Smart LED is a well-known technology that is sold commercially. The number

of light bulbs is the same as the number of the light bulbs in the baseline since the LED used in the simulation

has an equivalent 60W lighting, but only 10W for energy consumption.

Tubular light & Sky light

There are some complications from simulating tubular light and skylight since the equipment is not available in

the software. Therefore, lighting electricity reduction and the increase of the cooling need to be investigated

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separately. To simulate lighting demand reduction, all the lighting control in the light tube in the applied spaces

is connected to schedule instead of the occupancy for the baseline. The schedule is set to be off from 8.00-17.00

since it is assumed that there is enough daylight during that interval of the day. The windows with the same area

of commercial light tube and skylight were adapted in the software to find the increase of cooling due to this

equipment. By considering the occupancy schedule with the availability of daylight, two main areas were

considered suitable for installing light tube and skylight. These two areas are all the common room and

Bathroom 1 plus the corridor since these two zones are not connected to the windows and outdoor area leads

to low availability of daylight during the day.

Smart thermostat & controller

There are a significant number of smart thermostats in the commercial market. Most of the devices work in a

similar principle where they automatically turn on and off of the cooling and heating systems in advance

according to the availability of the occupants. At the same time, it adjusts the temperature and HVAC fan speeds

to control temperature and humidity by adjusting as specified by the user’s temperature preferences and in

relation to the indoor and outdoor climates. Nevertheless, some smart thermostats can detect the user’s

location and can be scheduled to turn itself on and off before the users arrive and leave the house to save energy

and minimize capacity since the air-conditioning does not have to cool or heat the house immediately. By

applying this principle, the set point of the temperature is determined to be a variable set point. The

temperature was set according to the availability of the occupants. In addition, it was set to start the cooling

system one hour before the arrival of the occupants and turn off (set at 30 C) at the time that the occupants

leave the room. The temperature during the occupancy duration was maintained between 24-26 degrees

Celsius. The thermal comfort of each room was controlled to not exceed 4% from the baseline since the thermal

comfort does not depend solely on the set point, but also on the capacity of the cooling system, which was kept

to be the same as the baseline. A larger capacity for the cooling system is needed for cooling the rooms down in

one hour. In the other words, the faster the cooling system lower the temperature, the larger the capacity is

required. The temperature set point was selected by considering the seasonal temperature as well. From the

beginning of June until the end of October, the ambient temperature is higher than the rest of the year. As a

result, a lower cooling set point is needed during the months to reach a temperature between 22-26 C. An

example of the cooling set points is shown in the Figure 48.

FIGURE 48 SHOWS THE COOLING SET POINT IN LIVING ROOM FOR ONE DAY

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Shading Automation

As already mentioned in the introduction, the exterior shading can decrease cooling consumption due to heat

gain through the windows. However, it is not a routine work for house owners to adjust the shading. Therefore,

the ability of scheduling and adjusting the shading according to the ambient condition is needed. The basic

concept of shading automation is to draw forth or retract the shading according to the sun. The sun control is

set by the IDA-ICE. The sun control means that the shading will be drawn only when there is no occupant and

the sun light exceeds the requirement of the room. Also, there are different types of shading in the software.

Almost all of the shading types are simulated to see the difference in the cooling demand reduction and the

increase of lighting consumption. From initial simulation of different shading types, only one type of shading was

selected according to the cooling demand, daylighting utilization and the availability of the Ghanaian shading

market. The type of shading selected is the exterior venetian blind. The properties of an exterior venetian blind

are shown in Table 8.

TABLE 8 SHOWS THE PROPERTIES OF EXTERIOR VENETIAN BLIND

Outside Inside

Total shortwave 0.35 0.35

Visible 0.35 0.35

Diffusion 1 0.35

Emissivity

Longwave 0.9 0.9

Thickness 1 mm

k 100 W/(K.m)

Door sensors

Door sensors can be used for the purpose of security. However, it can also be utilized as an energy reduction

device. The principle function of the sensor is to remind the users to close the inside doors when the air-

conditioning is on to limit the rooms being cooled and not cool the entire house. By applying this principle, the

energy consumption can be reduced. In the technology simulation, the doors were set to be "always close" to

represent the real condition when door sensors are applied.

Cooling systems

Waterborne fan coil

This cooling system can be used instead of conventional ductless air to air conditioning systems. Some

advantages like lesser environmental impact due to use of water as coolant instead of utilizing environmental

harmful refrigerant types, better control and monitoring by means of equipping the system with smart

thermostats and easier installation process make this system one of the favorites for our project. Installing an

outdoor unit which is called chiller and can be connected to several indoor units with humidity control ability

gives an irresistible chance to be utilized in our project. In addition, indoor units which can be installed on floor

give a better and evenly distributed temperature gradient over the zones in comparison with wall mounted

units. Furthermore, some models of fan coils can be installed in which it can introduce some amounts of outdoor

fresh air and recirculate used indoor air. In these models higher electricity consumption will be needed since

pre-process of humid hot air should be done before blowing to indoor.

Figure 49 demonstrate the designed cooling set points of fan coil system for different zones to cover the

cooling demand and achieve the desirable indoor climate.

62

FIGURE 49 SHOWS THE TEMPERATURE SET POINTS USED IN THE TECHNOLOGIES EVALUATION FOR FAN COIL SYSTEM

TABLE 9 SHOWS THE DESIGNED COOLING POWER FOR DIFFERENT ZONES OF THE THREE-BEDROOM HOUSE FOR FAN COIL

SYSTEM

Zone Design cooling power (W) Design cooling power (W/m2)

Kitchen 4000 277

Living Room 6000 210

Master Bedroom 3000 149

Bedroom no.1 3000 218

Bedroom no.2 3000 252

Studio 3500 234

Variable Refrigerant Flow or VRF

Unlike above mentioned technique this one utilizes refrigerant flow directly which can give a negative point

regarding to environmental considerations. Most of the VRF systems have R410A refrigerant type which has high

global warming potential (GWP). In contrast, lesser piping and refrigerant amount in comparison with multi joint

cooling systems give a better chance to this technique to be selected. However, according to our calculations

both the above mentioned fan coil and the VRF cooling systems have almost the same energy consumption if

we compare with conventional ones. The main reason is that we try to maintain the indoor climate,

temperatures and PPD, PMV values at the same level for all scenarios. Also, the COP2 value is assumed to be 3

in all of the scenarios included baseline and future ones.

Cooling panel

The last system is cooling panel technology. This system is being utilized mostly in commercial buildings since

humidity control is achieved by means of AHUs. The main advantage of the cooling system is its lower energy

consumption due to low or non-mechanical parts like fans or pumps in it. Evenly distributed temperature

gradient over the height of the zones and noiseless working principles are among its pros. However, the

humidity level in Accra is too high in most of the times which makes this technique vulnerable if there is no AHU

system in the place. Due to high initial investments and high electricity consumption, authors do not recommend

to use AHU to process the entering fresh air to the house. In other words, cooling panels can be very sensitive

to high indoor humidity and condensation. Table 10 shows the various properties of cooling panels used in IDA

ICE energy simulation software for every zone of the three-bedroom house.

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TABLE 10 SHOWS THE MAXIMUM DESIGNED COOLING POWER (W) AND CHILLED WATER MASS FLOW RATES (KG/S) IN THE

DIFFERENT ZONES OF THREE-BEDROOM HOUSE USING COOLING PANELS

Zone Maximum design power (W) Chilled water mass flow at full power (kg/s)

Kitchen 2000 0.14

Living Room 2500 0.17

Master Bedroom 2000 0.14

Bedroom no.1 2000 0.14

Bedroom no.2 1500 0.1

Studio 3000 0.2

Economic Evaluation of Technologies

The purpose of economic evaluation of technologies is to consider the economics of each technology should be

applied in the Economic scenario, as well as, in the Realistic scenario. The transportation and installation costs

are not included in the economic evaluation since some of the technologies are not available in Ghana, and is

subjective to the negotiation between the supplier and developer. To estimate the financial status of the two

systems, the incremental cost is applied to the calculation. An economic evaluation is highly affected since Ghana

is an early developing country; therefore, the discount rate can significantly affect the savings and investment

of the country. Only present value equations combined with cash flows were used in the economic evaluation.

Present value Equation 4 was taken from [120].

The equation for present value is;

EQUATION 4 FOR PRESENT VALUE CALCULATION

𝑃 = 𝐹1

(1+𝑖)𝑛 (4)

Where

P - Present value

F - Future value

i - Interest rate

n - Considered period

The technologies were analyzed by applying Present Worth Analysis, Payback Analysis and Benefit/Cost Analysis

according to [120]. All the analysis was performed by drawing cash flows in in combination with the Microsoft

excel financial function.

Cash flow was drawn over the lifetime of the devices, which was estimated by applying different parameters

according to Table 11 and Table 12. Since Ghana has a high development, the interest rate is significantly high

as 26% [121]. However, this value will not be constant forever and will decrease overtime since the development

will get close to the steady state. As a result, the interest rate was assumed to be decreasing 5% every year. On

the other hand, the energy price dramatically increases in some years since the economy of the country has

been growing dramatically, as the result of incoming increase of investment from industries [122], leading to

higher demand for energy. The rate of energy price was assumed to increase by 10% every year for the first ten

years for the assumption of the increase of the investment leads to the lack of energy supply. On the other hand,

the energy price may decrease by 10% every year for the last ten considerable years because of the expectation

of new power plants construction in the country. In the other word, deficit of electricity may be replaced by

surplus of electricity in the second decade of the project lifetime. The Ghana electricity price is not constant, but

decreases by the amount of electricity used. For the project, the electricity price is selected to be around 0.25

US dollar per kWh according to the 14 December 2015 residential electricity price by the Electricity Company of

Ghana Limited [123].

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TABLE 11 SHOWS THE FINANCIAL PARAMETERS

Technologies Incremental investment(USD)

Incremental maintenance cost (% of investment)

Lifetime(Year) Number of replacement in 20

years

Smart hub 95 0 10 2

Smart thermostat 1197 3 10 2

Wireless light bulbs

288 3 22 0

Occupancy sensor 320 3 7 2

Automated shading

3496 5 20 1

Door sensor 189 3 7 2

2 panes windows 162 0 20 0

3 panes windows 11858 0 20 0

Cooling panels 4548 0 20 0

Cooling fan coil 3236 0 20 0

Cooling VRF 1528 0 12 0

TABLE 12 SHOWS THE INITIAL AND CHANGING RATE OF DISCOUNTED RATE AND ELECTRICITY PRICE IN GHANA

Year Initial year First 10 years Last 10 years

Discounted rate (%) 26 10% decrease 10% decrease

Electricity price(USD) 0.25 5% increase 5% decrease

The prices of the devices were found from the different sources by searching retailer website and contacting

different suppliers. The prices of the devices vary from different suppliers and functions. Therefore, the median

of the prices was used for finalizing the price of each device. The range and median of the equipment price are

presented in Table 13.

TABLE 13 SHOWS THE RANGE AND MEDIAN OF EQUIPMENT PRICE

Devices Price range (USD) Median (USD)

Smart home hub 68-180 95

Smart thermostat 220-250 235

Regular thermostat 19-46 35

Wireless occupancy sensor 27-40 32

Connected light bulb 14-15 15

Tungsten light bulb 1.87 2

Tubular light 180-335 250

Shading automation 511.59 512

Door sensor 27-33 32

Price base on Amazon.com

Energy Simulation and Environmental Impact Reduction of the all Scenarios

In the energy simulation of scenarios, the purpose is to see the variable results when different technologies are

applied to the project as a system. Five scenarios were taken into account; Highest Energy Reduction, Realistic

with fan coil, Realistic with VRF, Economic and Economic Internet of Things (IoT). These will be called scenarios

one, two, three, four and five respectively. In scenario one, all the technologies that can decrease energy

consumption were applied into the simulation for finding the final energy consumption of all technologies

applied together. For scenario two and three, different technologies were considered in regards to the real

function, advantages, disadvantages and complication of the technologies that do not disturb the users in daily

life. For example, indoor door sensors can decrease some amount of energy demand, and it is also economical.

65

However, the technology was not applied to this scenario since it can interrupt the house owner all day through

mobile phone notifications which will be sent all the time when the occupants open and close the doors. This

sensor may be incorporated when future solution modifies it to be more suitable in reality. Also, two main

cooling technologies of waterborne fan coil and refrigerant based VRF systems were applied. According to our

findings and suppliers’ responses both technologies are realistic and can be easily implemented by local

partners.

The technologies in both Economic options, scenarios four and five, were considered according to the economic

evaluation of technologies. The economical technologies are applied to these scenarios, and final energy

consumption can be found. The different technologies applied to the different scenarios are simplified in Table

14. The CO2 emission per kWh electricity production for Ghana was taken and calculated [124]. The value used

in Ghana is 0.21476 kgCO2/kWh. The CO2 reductions from the scenarios were calculated by multiplying the

energy reduction results with this factor.

TABLE 14 SHOWS THE TECHNOLOGIES APPLIED TO SCENARIOS

Device Baseline Highest Energy

Reduction

Realistic with fan coil

Realistic with VRF

Economic Economic IoT

Smart thermostat

No Yes Yes Yes Yes Yes

Smart LED No Yes Yes Yes Yes Yes

Tubular light No Yes Yes Yes No No

Shading automation

No Yes No No No No

Door sensor No Yes No No Yes Yes

Windows Single pane Triple panes Single pane Single pane Double panes

Single pane

Cooling system

Split type AC Cooling panel

Fan coil water borne

VRF air-con Cooling panel

Split type AC

66

Results

The result will be presented in three sections: firstly, Energy Simulation and Economic Evaluation of

Technologies, secondly, Energy Simulation, CO2 emission and Economic Evaluation of the scenarios and lastly,

Effect of Different Factors on Energy Consumption. The results for four scenarios - Realistic with Fan Coil,

Realistic with VRF AC, Economic and Economic IoT – will be shown. Another objective is answered by the results

that occupants’ behavior slightly affects the energy consumption.

Energy Simulation and Economic Evaluation of Technologies

The result of this section presents ten technologies. The main technologies are Smart Thermostat, Smart LED,

Daylight, Shading Automation, Door Sensor, Windows, and Cooling System. Windows are considered separately

into two and three panes windows. In the same way for cooling system is also divided into Fan Coil Waterborne,

VRF AC and Cooling Panels. The result presentation will be in financial measurements - Incremental Investment

Cost, Net Present Value (NPV), Payback Period and Benefit per Cost Ratio for economic evaluation as in Figure

53, Figure 54 and Figure 55. The total energy consumption and energy consumption reduction will be shown in

Figure 50 and Figure 51 for energy simulation.

FIGURE 50 SHOWS THE TOTAL ENERGY CONSUMPTION OF THE TECHNOLOGIES

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Total Energy Consumption

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FIGURE 51 SHOWS THE ENERGY REDUCTION OF THE TECHNOLOGIES

The result shows most technologies applied to the baseline can reduce energy consumption of the implemented

house, except for tubular light, fan coil water born, and VRF which have energy consumption slightly higher than

the baseline. The energy consumption in the tubular light simulation does not decrease because the occupants

are not present in bathroom 1 and the corridor where daylight can substitute electrical light utilization during

the day according to the schedule setting. The energy simulation result was used to economically evaluate the

applied technologies into the Economic scenarios. According to the result, door sensors, shading automation,

smart LED, smart thermostat, triple panes windows and cooling panels will be applied to the Highest Energy

Reduction scenario.

FIGURE 52 SHOWS THE INCREMENTAL INVESTMENT COST OF TECHNOLOGIES

Figure 52 shows the incremental investment cost of the technologies replacing the traditional technologies. As

can be seen in the Figure 52, the highest incremental investment in the first four places are triple panes windows,

cooling panels, fan coil waterborne and shading automation. The investment of the rest of the technologies are

relatively low.

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FIGURE 53 SHOWS THE NET PRESENT VALUE OF THE TECHNOLOGIES

Considering cooling systems, only the cooling panel gives a positive NPV according to Figure 53. On the other

hand, smart LED, smart thermostat, door sensor and double panes windows give positive NPVs for the rest of

the technologies. The technologies giving positive NPVs will be included into the Economic Scenario.

FIGURE 54 SHOWS THE PAYBACK PERIOD OF THE TECHNOLOGIES

The payback periods are interlinked with net present value, but not completely since the payback period does

not take into account the income after payback. Only the technologies that have payback periods shorter than

the lifespan of the device will be included into the Economic scenario, which are the same technologies as the

NPV positive result. In Figure 54, the technologies without a payback period mean the technologies will never

get paid back. In other word, the technologies cannot reach the breakthrough point.

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FIGURE 55 SHOWS THE BENEFIT TO COST RATIO OF THE TECHNOLOGIES

The benefit to cost ratio defines the amount of investment compared to the amount of savings over the lifetime

period. The technologies that gives B/C ratio higher than 1 will be considered in the Economic scenario, which

shows a similar trend to the NPV result.

The different financial measures in these scenarios can provide the initial criteria for technology selection,

depending on the investor's point of view. However, the technologies that give positive NPVs, lower payback

periods than lifespan, and B/C ratio more than 1 will be taken into the Economic scenario. Figure 55 shows the

rate of the benefit to cost ratio for different applied technologies.

Energy Simulation and Economic Evaluation of Scenarios

In this section, all the financial parameters are similar to the Economic Evaluation of Technologies; the only

difference is the considered period. In the evaluation, a 20-year period was applied. Some devices to help

connect the system together were taken into consideration such as the Smart hub. The results are shown in five

different scenarios to show the energy reduction and financial measurements when the devices are combined

as a whole system. The five scenarios are Highest Energy Reduction, Realistic with Fan Coil, Realistic with VRF

AC, Economic and Economic IoT where IoT stands for Internet of Things. The technologies applied to each

scenario are explained in the methodology. The energy simulation results will be revealed in the energy

consumption reduction section in Figure 56. The incremental investment cost and the other financial

measurements are presented in Figure 58, Figure 59 and Figure 60.

-10123456789

10

rati

o


Benefit per Cost Ratio

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FIGURE 56 SHOWS THE ENERGY REDUCTION OF THE SCENARIOS

It can be seen in Figure 56 that the Highest Energy Reduction scenario has the highest energy reduction.

However, its energy reduction is slightly higher than the Economic scenario, whereas incremental investment

cost is relatively high compared to the Economic scenario.

FIGURE 57 SHOWS THE INCREMENTAL INVESTMENT COST OF THE SCENARIOS

Considering the incremental investment cost, Highest Energy Reduction requires the highest initial investment.

This illustrates that to have high energy reduction in return requires high investment. Thus, it is crucial to decide

the correct and most effective measure when selecting the different technologies for the project. For instance,

Figure 57 demonstrates that even though Highest Energy Reduction has the highest energy reduction, but the

scenario will not be utilized due to its negative NPV.

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Realistic withfancoil

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Scenarios

Energy Reduction of the Scenarios

0

5000

10000

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71

FIGURE 58 SHOWS THE NET PRESENT VALUE OF THE SCENARIOS

Figure 58 shows that the four scenarios that give positive NPV are Economic IoT, Economic and Realistic with

VRF and Realistic with Fan Coil. Considering NPV, the chart interprets that the four scenarios are economical. In

contrast, scenario one or highest energy reduction is not economical.

FIGURE 59 SHOWS THE PAYBACK PERIOD OF THE SCENARIOS

As it is seen in Figure 59, the payback period of the scenarios is not used in the decision-making, but it can be

used by investor/investors to have a general idea about the different scenarios' payback time.

-5000

0

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10000

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20000



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USD

Scenarios

NPV of the Scenarios

0

2

4

6

8

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Year

Scenarios

Payback Period

72

FIGURE 60 SHOWS THE BENEFIT PER COST RATIO OF THE SCENARIOS

According to Figure 60, it is clear that the Economic IoT scenario gives the highest benefit per cost ratio followed

by Economic, Realistic with VRF, Realistic with Fan Coil and Highest Energy Reduction respectively. The value

needs to be more than 1 in order to be considered as economical. All the financial measures show the same

trend. The preferred choice depends on the investor's requirement for investment.

The result shows four scenarios to be worth for the investment from an economical point of view: Realistic with

Fan Coil, Realistic with VRF, Economic and Economic IoT. However, it depends on the demand of the project

owner on which economic measures are suitable, as well as, technical limitations such as the technologies

applied to the Economic scenario.

FIGURE 61 SHOWS THE CO2 REDUCTION FROM THE SCENARIOS

Total CO2 reduction of each scenario is illustrated in Figure 61. According to our calculation the energy saving

per scenario directly relates to amount of reduction in CO2 produced by electricity generation processes

according to the modelling. As it is seen in the chart, in the first scenario, more energy reduction means more

CO2 reduction which follows by economic scenario, IoT scenario, realistic with VRF and realistic with fan coil.

0

1

2

3

4

5



Realistic with VRF Economic Economic IoT

rati

o

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Benefit per Cost ratio

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400

600

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1200

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1800



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kCO

2 p

er y

ear

Scenarios

CO2 Reduction

73

The Effects of Different Factors on Energy Consumption

Since the simulation result varies depending on many factors such as occupancy schedule, preferable thermal

comfort and quality of the indoor climate, some important factors were varied for investigating the effect of

energy consumption when different factors are applied. In this investigation, the occupancy schedule needs to

be varied since the schedule applied in the previous simulation is merely for two adults with two children where

only one person stays in the kitchen during the afternoon of weekdays without summer break. For further

understanding about occupancy schedule retired people and summer break were considered in the simulation.

Another factor is the air changed rate, which can significantly vary depending on the quality of the construction,

material, etc. The table shows the variables that can affect the energy consumption rate.

TABLE 15 SHOWS THE FACTORS AND FACTORS RANGE

Varied factor type

ACH Fixed ACH

ACH at 50 Pa

Schedule With summer time

Two retired with summer time

Indoor CO2 level is highly dependent on the above mentioned factors. Two different infiltration rates called

"fixed air changed rate" and "air change rate at 50 Pa called ACH50" are examined and results are shown as

below. Different occupancy schedules are implemented and results are achieved. Also different CO2 levels are

achieved depending on different infiltration rates.

FIGURE 62 SHOWS THE EFFECT OF TYPE OF OCCUPANCY SCHEDULE ON ENERGY CONSUMPTION

The Realistic scenario is adapted on different occupancy schedules. Results show the increase of energy demand

when two retired people with a summer occupancy pattern is applied. Figure 62 shows the rate of the energy

consumption with changing of occupancy pattern. According to the Figure 62, occupancy pattern slightly affects

the energy consumption. According to Figure 63, more ACH rates results in more energy consumption. It is

assumed that baseline infiltration is around 0.5 ACH at fixed rate around the year independent from outside

pressure variation and wind speed.

0

4000

8000

12000

16000

Realistic with regularschedule(New)

Realistic with summer Realistic 2 retired withsummer

kWh

/yea

r

Type of occupancy schedule

Effect of schedule changed on energy consumption

74

FIGURE 63 SHOWS THE EFFECT OF VARIABLE FIXED ACH ON THE ENERGY CONSUMPTION IN COMPARISON WITH BASELINE

FIGURE 64 SHOWS THE EFFECT OF VARIABLE FIXED ACH ON CO2 LEVEL

The proportion of the increase in energy consumption is less than one. This means that increasing infiltration

rate by 100 percent will result in an increase in energy consumption of less than 100 percent. Moreover, the

energy consumption does not increase linearly with the fixed ACH. In the same way, the indoor CO2 levels do

not linearly follow the percentage change of the infiltration rate. Figure 64 illustrates the effect of infiltration

rate versus indoor CO2 levels. It is clear that with increasing the ACH rate, indoor CO2 level decreases slightly.

0

10

20

30

40

50

60

1 2 4

% c

om

par

ed t

o B

asel

ine

Fixed ACH rate

Increase of Energy Consumption

0

100

200

300

400

500

600

700

800

900

1000

Fixed ACH baseline(ACH 0.5)

1 2 4

Max

imu

m C

O2

(pp

m)

Fixed ACH rate

Effect on indoor CO2 level

75

FIGURE 65 SHOWS THE EFFECT OF VARIABLE FIXED ACH50 ON THE ENERGY CONSUMPTION

As it is demonstrated in Figure 65, reduction in energy consumption is higher when the air change per hour is 1

at 50 Pa, following by 2 ACH, 4 ACH and 8 ACH, respectively. In other words, by increasing the ACH from 1 to 8

at 50 Pa, reduction in energy consumption is getting lower compared with baseline which has an infiltration

rate of 0.5 at fixed rate.

FIGURE 66 SHOWS THE EFFECT OF VARIABLE ACH50 ON CO2 LEVEL

Since the ACH at 50 Pa is tighter than the fixed ACH at the same value, the energy consumption with ACH50

decreases when ACH50 setting is applied. However, according to Figure 66, the indoor CO2 levels increase

significantly compared to the baseline. The result shows the sensitivity of energy consumption and CO2 level on

different types and values of infiltration rate setting. Both energy consumption and indoor CO2 level increase

and decrease in nearly logarithmic function by changing the ACH at 50 Pa from 1 to 8.

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

1 2 4 8

% c

om

par

ed t

o B

asel

ine

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Energy consumption reduction of ACH50

0

2000

4000

6000

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12000

Fixed ACHbaseline (ACH

0.5)

1 2 4 8

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imu

m C

O2

(pp

m)

ACH at 50 Pa

Effect on indoor CO2 level

76

Discussion

Technologies evaluation, scenarios evaluation and sensitivity analysis on the input factors will be discussed in

this part. According to the economic evaluation of the chosen technologies, five out of ten technologies - door

sensor, smart thermostat, smart LED, cooling panel and double panes windows - are economical. We created

five scenarios considering energy reduction, feasibility and economics point of views from the economic

evaluation of the technologies. Four out of five scenarios - Realistic with Fan Coil, Realistic with VRF AC, Economic

and Economic IoT - are economical. The technologies in both Realistic scenarios should be applied to the actual

project since they are carefully selected from economic, technical and local availability points of views.

Results show that if the existing challenges of economic scenario which are condensation in cooling panels and

price and desired quality of double glazed windows in Accra can be solved and achieved, respectively, economic

scenario would be interesting for the construction company.

The Economic IoT, which only applies smart control systems, gives the best economic value since the incremental

investment is low and provides a high return. Therefore, with an alternative cooling system and windows, the

Realistic with VRF scenario would be the most attractive in terms of suitability and economics because it gives

NPV, payback, and B/C of 4103 USD, 5 years and 1.74 respectively with incremental investment cost of

approximately 3,927 USD. However, considering economics and suitability without an alternative cooling system

and windows, the Economic IoT scenario would be the best option because it gives the three value in 17,242

USD of NPV, 2 year of payback and 4.18 B/C ratio with low incremental investment at 1,800 USD.

Another challenge of this project was due to limitation of the software. Since not all of the functions of the

equipment can be simulated in the IDA ICE, the results can slightly be different with the reality. However, it is

believed that utilizing IDA ICE software would be a suitable way of finding energy demand reduction and energy

consumption in the project that has yet to been built. In other words, the simulation gives a rough estimation

about energy use in houses.

Even though, IDA-ICE has not been made for simulating smart devices, it has some control functions that allow

the possibility of applying the smart device control principle. To our knowledge, no other research has been

conducted in a similar projects and climate conditions utilized our manner of approach. However, some of the

researches [9], [10], [97] carried out energy reduction from some devices such as lighting sensors and smart

thermostats by conducting a real measurement. Obviously, one of the limitations in our project was the lack of

on-site measurements which can bias the outcomes slightly.

One of the factors that can bias the simulation results is the wide occupancy inconsistency. It is almost impossible

to predict the occupancy pattern, which is very different from one household to another depending on the

behavior and number of occupants. Some research demonstrated that, even though the same principles are

applied for different products, the result differs significantly due to the inconsistency of the occupancy pattern

[94], [98], [100].

As a consequence of the factors already discussed, the result reviews some differences between analyzing,

reductions individually and in a combination. When considered individually, the smart thermostat and control

achieves a 14% cooling energy reduction, which is close to the 15% cooling reduction from Nest smart

thermostat [87]. However, when considered as a combination of both cooling and heating energy reduction

from different producers, the device yields 20% to 30% reduction. This occurrence is because only one main

principle of the device is applied, and it is only applied to the cooling system. [94]. In the meanwhile, a real

product would have different functions and can be applied to both heating and cooling system [94], [95], [97],

[98].

Another promising device is the smart LED, which shows a potential of 94% lighting demand reduction. The

result is in a different league when compared to 3% to 84% [76] of reduction from only applying the occupancy

sensor. From the range, both occupancy sensor and LED have been calculated to yield about 83.8% to 97.3% of

energy reduction, which are close to our simulation. However, one literature reported that savings from the

occupancy sensor can significantly vary due to occupancy pattern and the time delay setting [76].

77

Shading automation can decrease about 3% compared to the baseline which is different from the literature

review's 12.7% cooling reduction during summer time [125]. The inconsistent values may be due to the

differences in house design such as house orientation and windows to wall ratio. It is difficult to compare result

with another house with a different design and location. On the other hand, when shading automation was

simulated in this case, the already existing fixed shading led to further energy consumption reduction.

The door sensor has not been reviewed or investigated in any literature as an energy reduction device. But, the

main distinction from other experiments lies in the integration all of equipment and simulation as a system a

rammed-earth construction in a location with a hot and humid climate.

There were some limitations related to availability of price and data. Firstly, the price of the equipment is not

openly accessible and changes over time. Secondly, details of product price from the suppliers, as well as

transportation and installation cost of the equipment at the location, are difficult to procure made the economic

evaluation process more difficult for the authors.

One of the issues was the country's import taxation and the tax deduction policy requires experience and time

for data collection, as well as, insight into the country's law and regulation. The inconsistency of the products

available in the market was among the issues. Moreover, the energy simulation software IDA-ICE is created for

the purpose of energy demand estimation. In other words, the software is not directly for finding energy

reduction from using smart devices; therefore, not all smart device controls can be applied to the simulation.

The best way of estimating the energy reduction is to extract real measurements on an actual project since there

are a significant number of factors, such as occupancy pattern, that cannot be accurately forecasted.

This method can be applied to future projects when a project owner would like to consider the economics of

the technologies. The proposed scenario helps a project developer to consider the entire system instead of

analyzing only individual devices. This thesis can also be a reference for showing the economics of the devices

as a system when dealing with rammed-earth construction in hot and humid climate. Furthermore, this study

would be useful for sustainable development in the future.

78

Conclusion

The research aims to find which smart and sustainable technologies are economical and suitable for the

rammed-earth house project in Accra Ghana. The sub-objective is to find the CO2 reduction of the scenarios and

the effects of the occupancy pattern and infiltration rate. The research was done in three parts: technologies

evaluation, scenarios evaluation and sensitivity analysis of the factors. Two main steps - energy simulation using

IDA-ICE and economic evaluation - were done in the first and second part. The economic result of technologies

evaluation was taken for the Economic scenarios consideration. Ten technologies were evaluated in the first

part. Five out of ten technologies - smart thermostat, smart LED, door sensor, double panes windows and cooling

panels - are cost effective as defined as giving a proper value for NPV, payback period and B/C ratio. The

economical technologies were included into the Economic scenario. Authors created five scenarios based on

three perspectives: realistic, economic and energy reduction. Four out of five scenarios are economical under

the 20-year project lifetime. However, it is recommended to apply Realistic with VRF AC with Economic IoT for

the actual project since both these scenarios are economical and suitable. The three numbers (NPV, payback

period, B/C) of the scenarios are 4103 USD, 5 years and 1.74 respectively with 678 kCO2 reduction per year for

Realistic with VRF AC. In the meanwhile, 17242 USD, 2 years and 4.18 respectively with 1235 CO2 reduction per

year are achieved for Economic IoT. The result also shows that having two retired people with students in

summer time, increases only 5% of energy consumption approximately. The increase in air change rate of both

fixed and at 50 Pa lead to an increase in energy consumption and a decrease in indoor CO2 level drastically.

Future works At the end of the day, the method can be used for future projects and used as a reference for smart and

sustainable technologies in hot and humid climates with rammed-earth construction. The actual measurement

can be conducted to validate the accuracy of the simulation for adjusting the factors to be more precise. For an

ease of use as a reference in various condition, the simulation can be conducted in different location, type of

material and construction. The detailed simulation such as computational fluid dynamic and lighting simulation,

using numerical method, can be studied to understand and acknowledge the reasons of the energy saving and

waste to improve the technologies and design of the energy efficient house, as well as, using different software

to investigate the difference and accuracy when different software is used as a simulation tool. To be more

innovative, the future work could incorporate with architects for designing more energy efficient house adapting

different house designs. Accordingly, we expect that the future work can be done in order to obtain more

accurate method and strategy in order to predict and simulate future buildings for economical evaluation,

energy efficient and suitability analysis as a project refference.

79

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