Parametric analysis of alternative energy conservation measures in an office building in hot and...

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doi:10.1016/j.bu

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Building and Environment 42 (2007) 2166–2177

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Parametric analysis of alternative energy conservation measuresin an office building in hot and humid climate

Imran Iqbal�, Mohammad S. Al-Homoud

Architectural Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

Received 8 October 2005; received in revised form 5 December 2005; accepted 13 April 2006

Abstract

The growth of demand for electrical energy in the rapidly expanding towns, cities and industries exceeds the growth of the power being

made available. Therefore, energy conservation is becoming an increasingly important issue in Saudi buildings. The objective of this

study was to investigate the impact of alternative energy conservation measures on energy requirements in office buildings in hot–humid

climates. The study was conducted on a five-story office building located in Dammam, Saudi Arabia, which has been in use since 1998.

Different types of HVAC systems were selected and different feasible and practical operational energy conservation measures (ECMs)

were evaluated using the energy simulation software of Visual DOE 4.0. Previous studies conducted in this area were reviewed. Data was

collected through review of design drawings, building audit and the analysis of 4 years of utility bills. All the collected data was analyzed

and the utility bills data was used to calibrate the base case of the existing building using Visual DOE energy simulation software.

Conclusions and recommendations were developed for conserving energy using various appropriate ECMs in office buildings in hot and

humid climates.

r 2006 Elsevier Ltd. All rights reserved.

1. Introduction

Energy retrofits and the implementation of conservationmeasures can be cost-effective means of reducing energyconsumption in buildings. Changing building HVAC-operating strategies work equally well and can result insavings through reduced equipment sizes as a result of peakload reductions [1]. For Saudi Arabia, buildings take thelion’s share which could exceed 70% of the total electricenergy use in the country [2].

Al-Homoud [3] showed that 15%, 19% and 40% annualenergy can be saved in large, medium and small officebuildings through envelope thermal optimization in thehot–humid climate of Riyadh area. Similarly, for thehot–humid climate of Jeddah, annual energy savings of8%, 12% and 24% can be obtained for large, medium, andsmall offices, respectively. The electric demand is veryhigh during summer, mainly due to air-conditioning

e front matter r 2006 Elsevier Ltd. All rights reserved.

ildenv.2006.04.011

ing author.

esses: [email protected] (I. Iqbal),

pm.edu.sa (M.S. Al-Homoud).

consumption which is high due to lack of thermalinsulation in most of the Saudi buildings, as well as theabsence of other energy efficiency measures and loadmanagement strategies [4]. For instance, in a supermarket(954m2 air-conditioned floor area), located in the easternprovince of the country, 38% of energy is used annually byair conditioning, 42% is used in appliances and theremaining 20% is used for lighting [5].In the United States on the other hand, buildings

consume a significant portion of energy. Buildings con-sume nearly half of all the energy in the country forheating, cooling, and power, and it is estimated that nearly30% of this consumption could be saved by energyconservation and/or sustainable building design andoperations [6].According to other sources, more than 50% of all

delivered energy in Europe and the United States can beassociated with buildings. In the United Kingdom forexample, more than 60% of energy is used to condition theindoor environment [7]. Energy efficiency of air-condition-ing systems is clearly of global importance. Studies haveshown that in South Africa, approximately 20% of all

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ARTICLE IN PRESSI. Iqbal, M.S. Al-Homoud / Building and Environment 42 (2007) 2166–2177 2167

available municipal electrical energy is used in commercialand office buildings. Further studies have shown that airconditioning is responsible for a substantial share of energyuse (50%) [8]. Efforts to improve energy efficiency shouldtherefore not only concentrate on the design of the air-conditioning system but also include the building itself.Any building and HVAC thermal design tool should thusaddress, in an integrated manner, both the building and theHVAC system together with its control.

Simulation of HVAC energy consumption in buildings isof considerable interest and benefit to engineers andarchitects. Energy simulation programs can be used toanalyze cost-effective energy conservation measuresbefore the building is built or modified [9]. There are twobasic levels of energy analysis tools. Simplified energycalculations and detailed energy calculations. Simplifiedenergy calculations are represented by the degree-daymethod suitable for energy consumption estimates relatingto small buildings and the modified-bin-method, whichcan be used with better accuracy for estimating theenergy consumption of larger buildings. Detailed compu-terized energy calculations apply hour-by-hour energysimulation. Such programs are used to simulate the energyconsumption in a building and its sub-systems for everyhour of an average weather year [10]. They offer detailedanalysis of a building’s energy use accounting for allfactors such as building schedule, occupancy as well asbuilding mass. They also offer life cycle cost analysis withdifferent output options depending on the individualprogram.

2. Case study

A six-story newspaper headquarters office building isselected for this research case study. The building is locatedin Dammam, Saudi Arabia at 261 towards North and 501towards east. The total floor area of the building is12,500m2 and its floor-to-floor height is 5.25m. The wallsof the building consist mainly of 200mm concrete blockand 50mm polyutherine insulation. The roof consists of200mm concrete block and 50mm polyutherine insulation.The windows are double glazed with 12mm air space witha shading coefficient of 0.3 and a transmittance of 0.7. TheHVAC systems used in the building is constant air volume(CAV) system with 24 air-handling units (AHUs) servingthe different zones of the building. The cooling of thebuilding is provided by chilled water from the plantthrough four reciprocating chillers. All the chillers arecontrolled by the cooling demand of the AHUs. Eachchiller has six compressors, 10 fan motors and six chillerpump motors. Total capacity of one chiller is 739KW.Each floor has separate thermostat control. All theconditioned zones in the building have set points between23 and 25 1C for summer and 21 and 22 1C for winter. AllAHUs are controlled by timers and after 4 p.m. it is setclosed for some floors which usually become unoccupiedafter that time.

There are six elevators serving the building. The lightingsystem serving the building consists mainly of fluorescentlamps. The building is occupied with different officeequipment including personal computers, printers, scan-ners, and other electric equipment. Most of the building isused as offices with two conference rooms in each floor andone mosque on the first floor in addition to a cafeteria inthe ground floor.

3. Building energy audit

Each zone of the building was physically investigatedwith the cooperation of the building and O&M personnelin order to obtain information about the building lighting,equipment and occupancy. For the purpose of gettingdetails of building envelope thermal characteristics, thebuilding architectural and engineering drawings werereviewed. Details of the building physical and operationalcharacteristics are shown in Table 1 (Table 2).The equipment used in this office building includes

personal computers, small and large printers, Xeroxmachines, and few scanners. For calculating equipmentand lighting power densities, the following procedure wasadopted in accordance with ASHRAE recommendations[13]. For each zone of the building, the total number ofequipment and lighting fixtures was counted and usingASHRAE standards, the power densities of equipmentwere calculated. Total number of occupants was alsocounted. Complete details of building lighting, equipmentand people are shown in Table 3.Information about HVAC systems, AHUs and chillers

was collected as per the design data, equipment tags, aswell as the information provided by the building main-tenance personnel.From utility bills data, valuable information can be

obtained about building energy use which can be comparedwith target values or compared with similar buildings. Forthe investigated office building, utility bills for the last 4years from January 2001 to December 2004 were collectedon request from building officials. This data providedsufficient information about historical annual energyconsumption and also helped in calibrating the energysimulation program.Monthly energy consumption billing data for the 4 years

is presented graphically as shown in Fig. 1. As can be seenfrom the figure, it is clear that the electric energy useincrease during summer months when the outdoor airtemperatures are high. During winter months, electricenergy use was lower due to lower outside air temperatures.From the analysis of all 4 years utility bills data, it isobserved that there is a variation in monthly electric energyuse due to seasonal weather effects. The average energyconsumption was calculated as shown in Table 4. The datashows that the minimum energy consumption was found tobe in the winter months from December to March.The annual energy use indices for the building in

kWh/m2 are shown in Table 4. More annual electric

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Table 1

Physical characteristics of the building

Component Description

Wall 200mm concrete

50mm polyutherine insulation

Inside and outside layers

U-value ¼ 0.36W/m2k

Roof 200mm concrete

50mm polyutherine insulation

Inside and outside layers

U-value ¼ 0.36W/m 2k

Glazing Double-glazed 6/12/6mm

Blue color

U-value ¼ 3.5W/m2k

Shading coefficient ¼ 0.3

Transmittence ¼ 0.7

People (number of people) 271

Lighting 325W/m2

Equipment 455W/m2

Type of lighting Flourecent

Ventilation rate 7.5L/S/person

Infiltration rate 0.2ach

HVAC system Constant volume system

Total AHU’S ¼ 24

Each AHU power rating ¼ 7600W

Number of zones ¼ 24

Chillers Type ¼ reciprocating

Capacity ¼ 736KW

Number of chillers ¼ 4

Water supply temperature ¼ 7 1C

Water return temperature ¼ 13 1C

Set point temperature 22–25 1C (summer)

20–22 1C (winter)

Table 2

Details of building lighting, equipment and people

Floor name Zone name Lighting power den

(LPD) W/m2

Ground Developing sect. 25

Ladies sect. 10

Advertising sect. 15

Canteen and Training sect. 10

First Computer sect. 20

Mosque 5

Publication sect 20

Editing sect. 20

Second Political sect. 20

Assistant editor Sect. 20

Local news sect. 20

Sports sect. 20

Fourth Assistant Managing director 20

Accounting sect. and meeting

room

20

Administration 20

Maintenance sect. 20

Fifth Managing director 10

Meeting room 10

Chief editor 10

Office 10

I. Iqbal, M.S. Al-Homoud / Building and Environment 42 (2007) 2166–21772168

energy was found to be consumed in the year 2001 whichwas 410 kWh/m2 compared to the 315Kwh/m2 yr for theyear 2003 (Table 5).

4. Simulation program calibration

Visual DOE is developed by engineers architects andcomputer programmers. It was first released in 1994 andhas evolved over the years. Visual DOE emphasizes thebalance between the ease-of-use and the flexibility for userswith different levels of simulation skills and background.In a nutshell, Visual DOE has four major components, thewindows user interface, the building and HVAC database,

sity Equipment power dendity

(EPD) W/m2

NOP number of people

25 15

10 7

35 10

10 25

30 20

5 10

30 25

30 15

30 15

30 15

30 15

30 15

16 16

20 20

16 16

10 10

10 6

10 6

10 5

10 6

Table 3

Building average monthly energy consumption

Month Days Electric energy (kWh)

Januray 31 303148

February 28 287591

March 31 321329

April 30 335193

May 31 375885

June 30 387987

July 31 429496

August 31 441000

September 30 410327

October 31 373418

November 30 358390

December 31 309252

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Ele

ctri

c E

ner

gy

Co

nsu

mp

tio

n (

kWh

)

2001200220032004

Fig. 1. Building monthly 4 years energy billing data (2001–2004).

Table 4

The building four years annual energy use indices in kWh/m2/yr

Year kWh/year.m2

2001 410

2002 377

2003 315

2004 330

I. Iqbal, M.S. Al-Homoud / Building and Environment 42 (2007) 2166–2177 2169

the DOE-2 simulation engine, and the simulation diag-nostic and support tools. A base case model was developedusing all the collected information and calibrated based onmonthly energy consumption utility bills data for the year2002 as shown in Fig. 2. Accordingly, Dhahran weatherdata for the same year is used in the simulation program.

Initially, the monthly energy consumption for the basecase was as much as 22% different from the utility billsdata for the year 2002. Trials were made to manipulate theestimated input behavioral parameters such as set pointtemperatures, schedule of use and the infiltration rate toclosely match the base case monthly energy consumptionwith utility bill data for the same year for the initial andfinal trials as shown in Table 6. Different indoor set pointtemperature for winter and summer months were sepa-rately used. Schedules of people, lighting and equipmentwere adjusted and different infiltration rates were tried.Fig. 3 shows the final monthly electric energy consumptionfor the building base case model predicted by the VisualDOE 4.0 and the actual energy billing for in the year 2002.The results show that energy simulation program predictsthe energy use pattern of the building fairly well especiallyin the summer months which includes June, July andAugust which represent the critical air-conditioning usemonths of the year. The same figure shows the monthly

energy use data and the percentage difference between thebase case and the actual building energy billing data. Ascan be seen in the figure, there is less than 5% difference forthe months of June and August and a maximum of 10%difference for month of July between the simulationprogram and the utility bills data for the same year.These results are considered reasonably accepted in light

of the subjective in the building operational parameters.

5. Evaluation of alternative energy conservation measures

Based on the evaluation of energy use pattern of thebuilding, several energy conservation measures (ECMs)were analyzed. Energy conservation measures were classi-fied into the three categories of no cost, low cost and majorinvestment measures as discussed below.

5.1. No-cost measures

These are measures that can be implemented throughoperational and behavioral means without the need forsystem or building alterations and, therefore, do notrequire extra cost for their implementation. These includethe following three measures.

5.1.1. ECM # 1: set point temperature

In this ECM, the impact of indoor temperature settingon energy use is analyzed using the Visual DOE 4.0computerized simulation program. The cooling tempera-ture was set at 25 1C for summer and at 22 1C for wintercompared to the base case set point temperatures of 24 1Cfor summer and 20 1C for winter. This ECM resulted inannual reduction in energy consumption of 3% as shown inFig. 4.

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Table 5

Input data used for calibration of the simulation program

Component Base case Final base case

Insulated wall 50mm polyutherene insulation 50mm polyutherene insulation

Insulated roof 50mm polyutherene insulation 50mm polyutherene insulation

Double-glazed window (6/12/6mm) U ¼ 3.5W/m2K U ¼ 3.5W/m2K

SC ¼ 0.3 SC ¼ 0.3

SHGC ¼ 0.26 SHGC ¼ 0.26

Trasmittance ¼ 0.7 Trasmittance ¼ 0.7

Color ¼ blue Colour ¼ blue

Energy-efficient lamps 40W fluorescent type 40W fluorescent type

Set point temperature 23 1C for summer and winter 25 1C (summer) and 22 1C (winter)

Schedule of lighting and equipment 100% use of lighting and equipment Reduce the usage up to 60% during low occupancy and night hours

Inflitration rate 0.45ach 0.20ach

HVAC system Constant air volume system Constant air volume system

309132279227

395908358137

412620435000

475200461677420827

398040360642

270000

0

100000

200000

300000

400000

500000

600000

Jan

Feb Mar AprMay

June

July

AugSep Oct

NovDec

months

Ele

ctri

c E

ner

gy

con

sum

pti

on

(kW

h)

Fig. 2. Monthly utility bills data for the Year 2002.

Table 6

Characteristics of the building glazing systems

Base case (double-glazed 6/12/

6mm)

Low-emittance glazing (double-

glazed 6/12/6mm)

U ¼ 3.5W/m2K U ¼ 1.8W/m 2K

SC ¼ 0.3 SC ¼ 0.14

SHGC ¼ 0.26 SHGC ¼ 0.12

Transmittance ¼ 0.7 Transmittance ¼ 0.7

Color ¼ blue Color ¼ silver


5.1.2. ECM # 2: nighttime setback

In this ECM, the indoor air temperature was adjustedfor unoccupied nighttime to reduce the energy consump-tion which corresponds to 11:00 at night until 7 a.m. thenext morning. The indoor air temperature was set at 28 1Cfor summer and at 16 1C for winter during these hours. Inthis ECM, on an average, a 5% reduction in energyconsumption especially in summer months is achieved aspresented in Fig. 5.

5.1.3. ECM # 3: schedule of lighting and equipment

Scheduling of the operation of building lighting andequipment is normally ignored but important ECM inmany facilities. For the investigated building, lighting andequipment were used all the time during unoccupied andlow occupancy hours. In DOE 4.0 simulation program, theschedule of lighting and equipments were adjusted byturning off some lighting and equipments during unoccu-pied and low occupancy hours and as much as 5% monthlyelectric energy savings were achieved as shown in Fig. 6.

5.2. Low-cost measures

These are measures that can be implemented for buildingalterations or modifications and thus, extra but low cost isrequired for their implementation.

5.2.1. ECM # 4: insulated wall and roof

For the building under study, polyutherene insulation of50mm thickness is used in walls. The U-value of walls usedis 0.35W/m2C. To investigate the impact of additional

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Base case

Year 2002data

Fig. 3. Comparison of building simulation prediction and actual utility billing electrical use (2002).

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Set PointTemp

Fig. 4. Monthly energy savings results from applying set point temperature.


insulation thickness on energy conservation, polyuthereneinsulation of 75mm thickness was tried with a new U-valueof 0.26W/m2C. As a result, only 1% of electric energy canbe saved as a result of adding 25% of insulation thicknessas shown in Fig. 7. This measure is considered neitherpractical nor cost effective. This is in accordance with the

principle of diminishing returns of insulation thicknesswhere additional thickness does not save much after certainlevel as observed in these results.For the roof, polyutherene insulation of 50mm thick-

ness is used. The U-value of the roof is 0.35W/m2C.Polyutherene insulation of 75mm thickness was tried

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Night timeSetback

Fig. 5. Monthly energy savings results from applying nighttime setback mechanism.

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EPD & LPDSch.

Fig. 6. Monthly energy savings results from applying schedule of lighting and equipment (ECM # 3).


with a new U-value of 0.26W/m2C. Similarly, lessthan 1% of energy saving was achieved annually as shownin Fig. 8 because the current roof system is sufficientlyenough.

5.2.2. ECM # 6: more efficient glazing system

Using more energy-efficient windows (high R-value andlow emissivity) can be beneficial in both reducing theenergy use and improving the indoor comfort levels. Forthe existing building, double-glazed window is used with aU-value of 3.5W/m2C. The shading coefficient of the

glazing used is 0.3 and the solar transmittance is 0.7. As anenergy conservation measure, the existing glazing systemwas replaced with a low-emittance double-glazed window.Details of both existing and alternate glazing systemcharacteristics are shown in Table 7.The simulation results revealed, on an average, a 7%

reduction in energy consumption low-e every month withas much as 8% reduction achieved in summer monthsusing this glazing system as illustrated in Fig. 9. Suchsavings are achieved due to the large area of glass used inthe building. The glazing system plays an important role in

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InsulatedWall

Fig. 7. Monthly energy savings results from applying more wall insulation (ECM # 4).

0.4%0.7%

0.5% 0.7%

0.7% 0.7%0.8%

0.8%0.8% 0.8%

1.2%

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InsulatedRoof

Fig. 8. Monthly energy savings results from applying more roof insulation (ECM # 5).


energy use pattern for the building and for reducing theinternal heat gains. Although it might not be feasible toapply this glazing system for the existing building,however, this ECM can be applied for similar types ofoffice buildings with large areas of glass. However, initialcost factor has to be taken into consideration whenconsidering this system.

5.2.3. ECM # 7: energy-efficient lamps

Lighting for a typical office building represents on theaverage 40% of the total electrical energy use [12]. Thereare a variety of simple and inexpensive measures toimprove the efficiency of lighting systems. These measuresinclude the use of energy-efficient lighting lamps andballasts, the addition of reflective devices and delamping

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Base CaseGlazing

Fig. 9. Monthly energy savings results from low-e glazing (ECM # 6).

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Base CaseEnergy EfficientLamps

Fig. 10. Monthly energy savings results from using from energy-efficient lamps (ECM # 7).


(when the luminance levels are above the levels recom-mended by the standards). For the investigated building,40W fluorescent lamps are used. As an energy conserva-tion measure, fluorescent lamps with the power of 34Wwere tried and the resulting monthly electric energy savingsare shown graphically in Fig. 10. From the figure, on anaverage, a 4.5% reduction in energy consumption isachieved especially in summer months. Since it is im-practical to replace all lighting lamps with new energy-

efficient lamps at once, they can be replaced graduallywhenever the old lamps burn out.

5.3. Major investment measures

These measures require major financial investment fortheir implementation. They can be implemented throughsystem renovation or retrofitting to the office building orfor new similar projects.


5.3.1. ECM # 8: replacement of CAV system with variable

air volume (VAV) system

In the CAV system, all AHUs fans operate with constantspeed. They supply conditioned air through a constantvolume air supply system to the conditioned zones. Thesystem is designed to supply enough air to cool the buildingunder design conditions. As an energy conservationmeasure, changing the system to a VAV system reducesthe amount of air supply by all AHUs as a function of zoneload and normally results in less energy to condition thevarious zones. Variable speed drive fans are assumed in thealternate VAV systems in the investigated building usingthe simulation program, necessary rezoning was done onthe ground, first and fifth floors of the building. On theground floor, VAV system was applied to the canteen, theadvertisement section, the auditorium and the meetingroom. On the fourth floor, this system was applied to theadministration section and the meeting room. On the fifthfloor, VAV system was applied to the small offices and thethree meeting rooms. The simulation results of the newsystem arrangement are shown graphically in Fig. 11. Onan average, 13% reduction is energy consumption wasachieved for the summer months. This ECM can be usedmore effectively in future similar office buildings.

5.4. Energy use for combined ECMs

The annual energy use for the combined ECMs is shownin Fig. 12. From the presented simulation results, energysavings of up to 17% can be achieved by using the VAVsystem only. Energy savings of up to 15% can be achievedusing more insulated roofs and walls, more efficient glazing

22%

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VAVsystem

Fig. 11. Monthly energy savings results

system and energy-efficient lamps. As discussed above,energy-efficient lamps can be used gradually in the existingbuilding. However, more roof and wall insulation and newglazing system are not practical options for the existingbuilding.Conclusively, all no-cost measures can be applied to the

existing building which includes scheduling of lighting andequipment, set point temperatures and nighttime set backmechanism. These will result in about 13% annual electricenergy savings. For the low-cost measures, only energy-efficient lamps can be used gradually in the existingbuilding whenever, there are fused or burned lamps. Thiswill result in an annual energy savings of up to 6%. For thehigh investment cost measures, VAV system can beimplemented through thermal rezoning of the existingbuilding and an annual electric energy savings of about17% can be achieved. Finally, by implementing all thecombined ECMs, about 36% of electric energy can besaved annually.

6. Conclusions and recommendations

Based on the evaluation of various energy conservationmeasures using the Visual DOE-4 energy simulationprogram, the following conclusions and recommendationsare made.

6.1. Conclusions

1.

%

Mo

from

Increasing the current polyutherene insulation from 50to 75mm thickness for walls and roof constructionrevealed annual electric energy savings of only 2%.

19%

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using VAV system (ECM # 8).

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MoreInsulated

Roof

MoreInsulated

Wall

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Set PointTemp

NightTime

EnergyEfficientlamps

VAVSystem

Sch. OfLighting &

Equip

Alternatives

En

erg

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Fig. 12. Annual energy use for combined energy conservation measures.


Therefore, current level of insulation is considered to besufficient.

2.
Using low-e double-glazed window with a U-value of1.8W/m2C and SC of 0.3 instead of the U-value of3.5W/m2C and SC of 0.14 for the existing buildingrevealed an annual electric energy savings of about 7%which can be considered for new buildings or whenretrofitting of the existing building is necessary.
3.
Using set point temperatures for summer and winter of26 and 20 1C, respectively, revealed an annual electricenergy savings of 3%. This ECM is operational anddoes not cost anything for its implementation.
4.
Using nighttime set back with summer indoor airtemperature of 28 1C and winter indoor temperature of16 1C during nighttime from 11 p.m. to 7 a.m. in themorning revealed annual electric energy savings of 4%.Again, this ECM is operational and does not add muchextra cost for its implementation.
5.
Using a VAV system instead of the current CAV systemresulted in an annual electric energy saving of up to17%. For the existing building, each zone is served by aCAV system. The VAV system can be applied to theexisting building by performing thermal rezoning.
6.
Using 34W, energy-efficient lamps can reduce theannual energy saving by 6%. However, it is neitherpractical nor cost effective to replace all lamps withenergy-efficient lamps at once. They can be replacedgradually as they burn out over time.
7.
By adjusting the schedule of lighting and equipmentduring unoccupied or low occupancy periods, an annualelectric energy saving of up to 5% can be achieved. Thisoperational measure does not add extra cost.
8.
The combined effect of all energy conservation mea-sures can result in annual energy savings of as muchas 36%.
6.1.1. Recommendations

Based on the conclusions of this research work, thefollowing recommendations are made for the existing officebuilding as well as for similar future projects:

1.
It is strongly recommended that a nighttime setback isemployed.
2.
It is recommended that the schedule of lighting andequipment should be adjusted so that they are turned off


during unoccupied or low occupancy hours, duringlunch and other break times.

3.
It is recommended that a continuous dimming controlshould regulate the lighting level to benefit from daylight so that the luminance level especially in theperimeter zone remains constant. In this way, theelectricity consumption of the building can be reduced.Occupancy sensors should also be considered for light-ing system control.
4.
It is recommended to use low-emmitance double-glazedwindows for energy efficiency especially in large glazedbuildings in hot climates.
5.
It is recommended that energy-efficient lamps offluorescent type having a power of 34W or less areused. However, for existing buildings, these energysaving lamps can be used when existing lamps areburned or fused.
6.
Air-conditioning systems play an important role inenergy consumption especially in summer. As the loadchanges or the weather becomes extreme in summer andmild in winter, it is strongly recommended that a VAVsystem is used as system renovation takes place in suchexisting buildings and should be considered for futuresimilar office buildings.
Acknowledgement

The authors would like to acknowledge the supportand facilities provided by King Fahd University ofPetroleum and Minerals (KFUPM) that made this researchpossible.

References

[1] Carriere M, Schoenau GJ, Besant RW. Investigation of some large

building energy conservation opportunities using the DOE-2 model.

Energy conversion and Management 1999;40:861–72.

[2] Hasnain SM, Smiai MS, Al-Ibrahim A.M, Al-Awaji. Analysis of

electric energy consumption in an office building in Saudi Arabia.

ASHRAE Transactions 1997; 103 (Part I): 173–84.

[3] Al-Homoud MS. Optimal thermal design of office buildings.

International Journal of Energy Research 1997;21:941–57.

[4] Smiai SA. Effective tools toward electrical energy conservation in

Saudi Arabia. Energy conversion and Management 1998;39:1337–49.

[5] Hasnain SM, Alabbadi NM. Need for thermal storage air condition-

ing in Saudi Arabia. Applied Energy 2000;65:153–64.

[6] Clarke JA. Assessing building performance by simulation. Building

and Environment 1993;28:419–27.

[7] Tham KW. Conserving energy without sacrificing thermal comfort.

Building and Environment 1993;28:287–99.

[8] Mathews EH, Botha CP, Arndt DC, Malan A. HVAC control

strategies to enhance comfort and minimize energy usage. Energy and

Building 2001;33:853–63.

[9] Donald W, FAIA, Kenneth L. Energy-efficient buildings, principles

and practices. New York: McGraw-Hill; 1983.

[10] Al-Rabghi OM, Hittle DC. Energy simulation in buildings: Overview

and BLAST example. Energy conversion and Management

2001;42:1623–35.

[12] Santamouris M, Argirious A, Balaras C, Gaglia A. Energy

characteristics and savings potentials in office buildings. Solar Energy

1994;52:59–66.

[13] Krarti M. Energy audit of building systems. New York: CRC Press;

2000.

Further reading

[11] American Society of Heating, Ventilating, and Air-Conditioning.

ASHRAE handbook of fundamentals. Atlanta, GA, USA: ASHRAE;

2001.

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