Building Performance Modelling -...

M. A. Schnabel (ed.), Back to the Future: The Next 50 Years, (51st International Conference of the Architectural Science Association (ANZAScA)), ©2017, Architectural Science Association (ANZAScA), pp. 207–216.

Building Performance Modelling

Parametric Study of Energy Optimization for Office Retrofit in the Tropics

Runddy Ramilo1, Sambit Datta2 and Mohamed Rashid Embi3 1 International Design Associates, Singapore & Curtin University, Australia

[email protected] 2 Curtin University, Australia [email protected]

3 Universiti Teknologi Malaysia, Malaysia b‐[email protected]

Abstract: Buildings are accounted for approximately 40% of global energy consumption and one‐third of global greenhouse gas (GHG) emissions. A significant proportion of energy utilization is due to the spread of heating, ventilating, and air conditioning (HVAC) installations in response to the growing demands for better thermal comfort of the built environment. While the proportion of energy consumption of buildings is an issue, architects have not seriously considered to innovate new solutions to tackle the problem particularly existing office building which is centrally airconditioned and consumed substantial amount of energy. Only few has been research to improve its performance to save energy that can be used as bench mark for post occupancy evaluation for existing buildings. To elucidate this issue, this paper is a result of a case study using building performance simulation tool to optimized energy for an actual office retrofit project in the tropics. Its objectives are to explore an energy optimization strategy using building performance simulation tool (IESVE) and to improve existing office building envelop for utmost energy efficiency. The result revealed that using parametric methodology through building performance simulation tool, an office building has the potential to achieve 26.8 % energy savings. Keywords: Building Performance Modelling; building envelop; energy efficiency; office building retrofit.

1. Introduction and Background

Increasing concerns about global warming present the building industry with a challenge to cut its energy consumption (Chenvidyakarn, 2010). It was evident that the building sector consumes 40%‐50% of the total delivered energy (EPA, 2004), (DTI, 2003). Building environment control systems like ventilation, cooling and heating can be fared as much as 70% of the total energy used (BRESCO, 2000). However, this energy consumption can be reduced significantly by utilizing passive design solutions instead of active mechanically designed buildings. For instance, a building engineered for tropics can only consume one third of the energy consumed by an air‐conditioned building (BRESCU, 2000), (Chenvidyakarn, 2010) while providing comparable level of thermal performance. This is because building in the tropics must be designed to adapt climate and take better advantages (Chenvidyakarn, 2010) of natural energy resources

208 R. Ramilo, S. Datta and M. R.Embi

such as wind and thermal buoyancy to help provide acceptable thermal comfort specifically in the tropics where heat of interior environment of a building is a challenge.

The Tropics is regarded as a region where humans evolved and comfort has often been taken for granted, built environments are increasingly becoming issues of public concern (Ossen et al, 2008). The tropical indoor environment and thermal comfort has been regarded as important as outdoor in the life of the populace which is remarkably evident in the vernacular architecture of the region. However, today many cities in the region experienced rapid urban growth often without much reference to the evolving urban environment. This tendency has put increased demand on the comfort requirements in the design of buildings. Comfortable outdoor spaces have a significant bearing on the comfort perception of the indoor ambience (Ossen et al, 2008). The demand for comfort conditions in buildings are significantly increased as a result of exposure to uncomfortable indoors. Achieving thermal comfort for building engineered for tropics in hot humid climates is indeed a challenge (Chenvidyakarn, 2010), (Suebarto, 2006). Point out by experts, tropics is characterized by relatively high temperature and high humidity. These difficulties lead to many buildings relying for air‐conditioning. However, range of passive design techniques such as design for minimizing cooling requirement and building massing (Wong, 2010), the use of shading device (Garde et al, 2001), (Laopanitchakul et al, 2007), material, color and texture (Leaurungreon et al, 2005), vegetation (Chen and Wong, 2006) cooling and ventilating techniques (Givoni, 1991), (Tantasavasdi et al, 2007), thermal mass (Hunt and Linden, 2004), radiant cooling (Givoni, 1994), indirect evaporative cooling (Givoni, 1980), (Bourne and Hoeschele, 1992) was already developed and framed but existing office building in the tropics has not been taken into account.

2. Objectives

Advances in digital technologies particularly building simulation environments have focused on algorithm development, data management and interfacing that are analysis based and support independent domain activities (Malkawi, 2004), (Ramilo & Embi, 2013). Currently, there is a broad range of simulation packages (Energy Plus, TRNSYS, Ecotect, IES and COMIS) that evaluate multiple thermal performance for buildings (Ramilo & Embi, 2013) (Luther, 2003). To shift the emphasis of these tools from analysis only to a combined model of analysis and synthesis a renewed research into advances in optimization is underway (Kolarevic et el, 2006). It integrates digital simulation tools to support performance driven design using optimization and partial automation (Pitts et al, 2008). Methods to assist in the coupling of design geometry with building performance simulation and the prediction of the performance of building envelopes (Luther, 2000), (Luther et al, 2007), (Ramilo & Embi, 2016) are being undertaken.

One research that have employed the used of digital technology (Ecotect) was Ossen et al (2010) to evaluate and measure thermal performance in indoor environment in their tropical building design project. The thermal comfort study involved the use of field and combination with Ecotect software. Validation of Ecotect was done by comparing the computer simulation result with the field measurement. Likewise on the research of prediction of thermal performance of facade residential buildings in Singapore (Liping, 2006), a conflation of digital technologies were used such as computational fluid dynamics (CFD and building simulation program (ESP‐r) to simulate thermal performance. The coupling program was validated by a series of validation studies, including single zone case, multi‐zone cases, and field measurement studies. The result have shown that the coupled simulations can produce much better results that building simulation alone especially in the aspect of indoor air velocity prediction (Liping, 2006).

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Building Performance Modelling Parametric

However while different research of building performance modelling is evaluated during schematic and design phase of a building project, only few has been research for existing office building to improve its performance and save energy particularly for actual office retrofit project that require building simulation tools to evaluate iterations of building envelop for final decision making and provides better understanding of how building performance simulation tool can evaluate façade design and in a way improve its performance. To elucidate this issue, this paper is a result of a case study made from an actual office retrofit project in Singapore to improve energy efficiency through improving existing building envelop. This study elucidates design methodologies that can be used either in design stage of the project or post construction performance evaluation to improve building design using building performance simulation tool (IESVE). Specifically, its main objective is to improve existing office building envelope and explore energy optimization opportunities to improved energy efficiency of 25% to 30% energy savings.

3. Building Performance Modelling for Energy Optimization

Building performance modeling is defined as an expression of measurable variables which affect a process or procedure. Common building performance factors are environmental such as solar gain, aerodynamics and heat loss, structural factors such as load and stress, and social factors such as view and privacy (Gunay et al, 2013). This includes finding sustainable and green strategies using new digital technologies that simulates building performance or 4D digital technologies that is available in the market. 4D digital technologies are commercial software (Ramilo & Embi, 2013) that can evaluated and stimulate daylighting, heat, energy efficiency, air flows, and indoor humidity. It helps and allow the design teams to provide quality information that is needed to quantify iterative choices, so that design teams can develop innovative green solutions at schematic phase of building design.

One notable project which have utilized building performance modelling for energy efficient responsive facade was Hanwha Headquarters in Seoul, Korea designed by UN Studio done to mitigate heat flow, optimized facade assembly and increase thermal comfort of its interior spaces (Figure 2).

Figure 2: Hanwha Headquarters, Seoul, Korea by UN Studio (Littlefield, 2008).

The high‐rise Hanwha’s headquarter building was mainly a renovation and re‐modeling of the facade which includes refurbishment of its interior public spaces, meeting floors, theatres and executive areas, along with the redesign of the landscaping. UN Studio’s design concept of the building resulted to be a


responsive facade which valued and integrates important key variables: program (exterior and interior), indoor climate and environmental considerations. The existing facade of the building contains single layers of dark glass and horizontal bands of opaque paneling. UN Studio decided to replace by clear insulated glass and aluminum framing to accentuate views and daylight. It’s framing and geometry is defined by the sun and orientation factors to ensure user comfort inside and to be able to reduce energy consumption. The facade workflow module distribution by UN Studio is presented in Figure 3.

Figure 3: Facade workflow module distributionby UN Studio (Littlefield, 2008).

While the upper portion of the south facade is angled to receive direct sunlight, direct solar impact on the building was reduced by shading which is provided by angling the glazing away from direct sunlight. At south and southeast where there is direct sunlight, photovoltaic cells are placed on the opaque panels on the façade. The challenging part on this process is that even a small variation of the parent geometry of the panel quickly results in an avalanche of child modules, which makes it necessary to develop a tool to automatically generate all possible facade unit variations panel. The idea of developing a “Unit‐Maker Tool” through scripting is helpful to takes basic geometric input information such as transom position, mullion dimensions, glass properties, and outputs numerous facade units.

3. Methodology

The scope of the case study dealt with exploring energy saving opportunities through improving building envelop of an existing 9‐storey centralized office building located on the west of Singapore with a gross floor area of 18,879 square meters, with north‐south orientation and window to wall area ratio of 0.57. The exploration was focused on how to improve the existing facade to minimize heat gain, improve day lighting and to minimize energy consumption. The exploration was done in four modified steps 1) post occupancy evaluation and measurements, 2) 4d modelling through IESVE, 3) building performance evaluation and 4) decision making which is briefly explain in 3.1, 3.2, 3.3 and 3.4

3.1 Post Occupancy Evaluation and Measurements

The first step of the exploration was to evaluate the existing office building. This was done through assessing the architectural plans and evaluating the data such as area of spaces and record of energy consumption. These data (Figure 4, 5 & 6) were collected, analyzed, validated and subsequently used in 4d modeling.

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Figure 4: Photo and existing plan of the project

Figure 5: Space areas of the project

Figure 6: Existing building energy consumption


3.2 4D‐Modelling Using IESVE

A 4d model was made using the verified architectural plans, sections, elevations and interior spaces of the existing office building project through IESVE (Figure 7). It was made to simulate the existing building orientation and other site condition.

Figure 7: 4d model of the existing project

3.3 Building Performance Iterations

When the baseline 3d model was verified, three (3) options of different new facade including the existing office building was modelled as shown in figure 8, made to evaluate the new facade design in terms of energy efficiency. Building performance simulation experiments of three façade options through IESVE was made, evaluated and assessed on the basis of efficiency and accuracy of thermal performance results. Quantitative data was statistically compared on existing building and each proposed retrofitted building envelop and energy consumption was recorded and analyzed (Figure 9). This was done to further improve the facade and explore the possibility of reducing energy consumption.

Figure 8: 3d Models of existing building envelop and the three proposed retrofitted building envelope 1, 2 & 3 showing its WWR and ETTV

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Figure 9: Comparison of energy consumption of proposed building Envelope 1, 2 & 3.

3.4 Decision Making

After the building performance simulation of the new three (3) proposed façade was made, relevant data related to energy efficiency and daylighting was carefully analyzed, verified and final decision was made as to which among the three (3) options is best to utilized.

4. Results

Considering energy efficiency, the proposed retrofitted building envelop 3 with the WWR of 0.40 and ETTV of 30.90W/m2 as shown in figure 10 was chosen as the final design façade design. It is because retrofitted building envelop 3 has the highest amount of energy savings (26.8%) among the three models that was presented in Figure 8. A comparison of cooling load savings of proposed building between envelope 1, 2 & 3 is presented in Figure 11.

Figure 10: Comparison of existing building envelope and proposed retrofitted building envelope 3 as final design

It was reiterated that the rate of heat transfer through the building envelop was depended on the difference of value between the outside temperatures and the temperature of the interior of the building


and the capacity of the facade to control heat flow and heat transfer. Factors that influence heat flow within the facade is mainly the overall thermal resistance, window to wall ratio (WWR), and envelop thermal transfer value (ETTV). It is also worth noting is that building envelop with high WWR is likely to have greater effect of the thermal comfort than with low WWR. The optimal WWR must importantly consider the layout of the space, smaller WWR must be used for spaces where users are near to the penetration for the building envelop facing south.

Figure 11: Comparison of Cooling Load Savings of Proposed Building Envelope 1, 2 & 3.

Figure 12: Proposed retrofitted building envelope 3 showing the additions of 4 x 300 mm external shading device and how it affects ETTV.

During the simulation, it was evident that facade elements like windows and light shelves is very significant in as far as thermal fluctuations is concerned. Heat transfer can be dictated the combination of the interior skin temperature of the glazing including the transmitted ultra violet rays through the glazing. This can be significantly influenced by the glazing units, the material properties of the glass, and the

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effectiveness of the light shelves used above the window (Figure 12). On the iterations, it is noted that light shelves on the south facing building envelope of building remarkably increases the daylighting quality and quantity. It reduces cooling cost, efficient daylighting approach by means of light, increases light penetration and therefore decrease artificial lighting during day time. It is the most effective in south facing envelope, improves daylight penetration, creates shading near the window, and helps reduce window glare and ultimately decreases the cooling load.

5. Conclusions

Building performance modelling play a crucial role in the decision making for designing an energy efficient building retrofit because it help investigate design options prior to construction. It is good tool to assess energy efficiency, environmental and energy impacts of design decisions. Without a doubt, it is an essential part for designing sustainable performative building envelope. In an office retrofit building project where energy is a concern, building performance simulation tool can quantify and predict energy consumptions and can be further reduced through building envelope iterations. It helps establish metrics that can be utilized to measure improvements by using different design strategies. In the case of this study, it is concluded that building performance simulation has an ability to quantify the impact of a design solution like the performance building envelop that can be investigated with actual quantifiable data, not just through theories, and able to analyse, predict energy consumption and saving, and lastly improve architectural design with multiple design alternatives.

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