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Energy and Buildings 43 (2011) 770–778

Contents lists available at ScienceDirect

Energy and Buildings

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eview

nergy consumption and the potential of energy savings in Hellenic officeuildings used as bank branches—A case study

iorgos N. Spyropoulosa,∗, Constantinos A. Balarasb

Technical Department of TT Hellenic Postbank, Aristidou 1, GR 10559 Athens, GreeceGroup Energy Conservation, Institute for Environmental Research & Sustainable Development, National Observatory of Athens, I. Metaxa & Vas. Pavlou, GR 15236 P. Penteli, Greece

r t i c l e i n f o

rticle history:eceived 3 June 2010eceived in revised form 6 December 2010ccepted 14 December 2010

a b s t r a c t

Energy performance of non-residential buildings and in particular of office buildings used as bankbranches is very limited. This paper presents new data from 39 representative bank branches and resultsfrom a more in-depth analysis of information from energy audits in 11 typical bank branches throughout

eywords:nergy consumptionffice buildingsank branches

Greece. The data was used to derive practical energy benchmarks and assess various energy conservationmeasures. Accordingly, the average annual total energy consumption is 345 kWh/m2. The breakdown ofthe different end-uses reveals that HVAC averages 48% of the final energy consumption, lighting aver-ages 35% and other office and electronic equipment average 17%. The most effective energy conservationmeasures reach annual energy savings of 56 kWh/m2 by regulating the indoor set point temperature,

nergy conservationank buildings

while the use of HF electronic ballasts and CFL lamps may save about 22 kWh/m2 and 29 kWh/m2 withand without the use of the external marquee sign, respectively.

© 2010 Elsevier B.V. All rights reserved.

ontents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7702. Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7713. Energy consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7714. Energy conservation measures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 774

4.1. ECMs for lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7744.1.1. Scenario A: replacement of the old conventional ignition systems with HF electronic ballasts and the incandescentlamps with CFL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7744.1.2. Scenario B: reducing the operating hours of the external marquee sign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7754.1.3. Scenario C: reducing the number of lighting fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 775

4.2. ECMs for HVAC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7754.2.1. Scenario A: adjusting the indoor set point temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7754.2.2. Scenario B: installing new insulated double glazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 775

5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7766. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 777

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 777References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 777

. Introduction considering the total electrical and thermal energy consumption,

The European building sector accounts for 38.7% of the totalnal energy consumption (1177.4 Mtoe in 2006) in the Europeannion (EU-27) of which 304.9 Mtoe in residential buildings and50.3 Mtoe in non-residential (NR) buildings [1]. At the same time,

∗ Corresponding author.E-mail addresses: gspir1@hotmail.com, gspir@tellas.gr (G.N. Spyropoulos).

378-7788/$ – see front matter © 2010 Elsevier B.V. All rights reserved.oi:10.1016/j.enbuild.2010.12.015

buildings account for about a 30–50% of the total energy related tocarbon dioxide (CO2) emissions [2].

The tertiary sector (NR buildings and agriculture) is among thefastest growing energy demand sectors and is projected to be 26%higher in 2030 than in 2005, compared to only 12% for residential

buildings [3]. The growth of energy needs in the tertiary sector,or more than 90% of the additional energy requirements, is drivenby the evolution of NR buildings. The breakdown of final energyconsumption by end use in European NR buildings is dominated

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G.N. Spyropoulos, C.A. Balaras / En

y space heating and other heat uses (73% in 2000 projected toecrease to 62% in 2030), 16% for electric equipment (projected to

ncrease to 27% in 2030), 6% for cooling (projected to increase to.3% in 2030) and 5% for lighting (projected to further decrease in030 as a result of widespread penetration of efficient lighting).lectrical energy consumption in NR buildings exhibits a constantncrease over the years due to the extensive use of HVAC and officequipment (especially electronic devices and computers) and isxpected to increase from 42% in 2005 to almost 50% of the totalnergy consumption in 2030.

In Greece, the building sector consumed 7.6 Mtoe or 35.4% of thenal energy consumption in 2006 compared to 3.8 Mtoe or 26.1%

n 1990 [1]. The Hellenic residential buildings, account for about5.7% of the total final energy consumption and consume 32.7% ofhe total electricity generated in the country and 21.5% of the totalhermal energy [4]. The Hellenic NR buildings account for 9.7% ofhe total final energy consumption and consume 29.7% of the totallectricity generated in the country [5].

The need to gain some insight and investigate the potential fornergy conservation in Hellenic office and commercial buildings islso in line with the ongoing efforts to comply with the Europeanirective on the energy performance of buildings – EPBD (2002/91)nd its national adaptation as part of the L.3661/19.5.2008 andhe Common Ministerial Decision 5825/9.4.2010 that specifies theechnical regulation (KENAK). Moreover, the European Directive onnergy end-use efficiency and energy services (2006/32/EC) neces-itates from all EU member states to adopt measures in order toimit the carbon dioxide emissions as well to achieve an overallational indicative energy savings target of 9% by 2017.

Most of our knowledge and available data on the energy con-umption and the assessment of energy conservation measures isvailable for residential buildings, while even fundamental knowl-dge of the NR building stock and its energy performance is ratherimited [5,6]. Office buildings are classified among the buildings

ith the highest energy consumption. The annual energy consump-ion in European office buildings varies from 100 to 1000 kWh/m2

f conditioned floor space [7], depending on location, construction,VAC and lighting installations, use and type of office equipment,perating schedules, etc. Typical annual total energy consump-ion in Hellenic office buildings averages 187 kWh/m2 [8]. In China,nergy use ranges from 70 to 300 kWh/m2 in large scale (20,000 m2

r more) public NR buildings with centralised HVAC systems [9].ost detailed data is available for buildings in the United States. The

verage energy use intensity in U.S. office buildings is 293 kWh/m2

10]. Detailed information on the energy consumption of represen-ative U.S. commercial buildings is collected by the U.S. Commercialuildings Energy Consumption Survey [11]. According to the mostecent published data for 2003, the annual gross energy inten-ity for office buildings is in the range of 220–360 kWh/m2 forhe different US climatic zones. Among the different office sub-ategories, banks and other financial offices are the most energyntensive averaging 301 kWh/m2 and the highest electricity con-umption intensities reaching a median of 239 kWh/m2, with a 25thercentile building level electricity intensity of 156 kWh/m2 and a5th percentile of 318 kWh/m2. However, similar data for Euro-ean buildings is very limited and there has been no publishedata on the energy consumption of buildings used in the bankingector. This paper provides relevant data on the characteristics ofhe Hellenic commercial/office buildings used in the banking sec-or as financial offices and contributes with new data on the energyerformance for this specific end-use of NR buildings.

. Methodology

The methodology to investigate the energy behavior of the bankranches and to collect, classify and process the necessary data,

nd Buildings 43 (2011) 770–778 771

included the following major steps:

• Energy consumption data: Electricity bills or utility records from39 bank branches throughout the country, over a period of 6years, were collected and classified. The classification was per-formed for the different national climatic zones. Practically allof the bank branches have only electrical energy consumption;only one branch had also a low thermal energy consumption forheating.

• Selection of typical branches: A representative sample of 11 typ-ical branches was selected for an in depth analysis and study. Thecriteria for selecting the specific branches included: location forcovering the different national climatic zones, completeness ofavailable data and similar functions of bank services (for examplesimilar operating hours).

• Energy audit: An in-depth investigation of the selected 11 typ-ical branches included an energy audit to collect the necessarydata, i.e. architectural drawings along with specifications for thebuilding’s envelope construction, the floor area and volume, allelectromechanical (E/M) installations for the different end-usessuch as the HVAC system, the lighting system, the electricalequipment, etc.

• Benchmarking: Based on the collected data and the results ofthe analysis, energy related indicators were estimated. Theseindicators for the 9 branches include: (a) the energy consump-tion per unit area (kWh/m2) and (b) the energy consumptionper unit volume (kWh/m3). For the sample of the 11 typicalbranches the additional findings include: (a) the breakdown offinal energy consumption, (b) the installed power per unit floorarea (W/m2) for lighting, equipment and HVAC systems and(c) the energy intensity expressed as energy consumption peremployee (kWh/emp).

• Energy conservation potential: Several energy conservation mea-sures (ECMs) were evaluated for the 11 typical branches.

• Cost effectiveness of ECMs: The financial evaluation (where appli-cable) of different ECMs was based on the Simple PayBack Period(PBP) and the Net Present Value (NPV).

• Environmental impact: The environmental impact assessmentwas based on estimated CO2 emissions before and after the imple-mentation of the various ECMs. The conversion between electricalenergy consumption and CO2 emissions was based on specificnational average conversion factors of primary energy consump-tion for power generation (0.950 kg CO2/kWhel).

Since many of the bank branches often consist of several levels(ground floor, basement, and mezzanine) it is necessary to clar-ify some of the assumptions. The energy audits of each branchrevealed that only the working area (ground floor) of each branchis air-conditioned. Therefore, since the vast majority of both theequipment and HVAC systems are located on the ground level,both the unit floor area (m2) and unit volume (m3) in the energyrelated indicators (kWh/m2, kWh/m3) refer to the working (air-conditioned) area which can be regarded as representative for theenergy performance of each branch. Since the basement (whereit exists) and the mezzanine (where it exists) are used as ancil-lary spaces, but both have an installed lighting system, the relativeindicators for lighting refer to the total floor area (ground floor,basement, mezzanine) of each branch, which usually differs fromthe air-conditioning area. The installed power per unit floor area(W/m2) of the equipment refers to the ground floor area and thatof HVAC refers to the working (air-conditioned) floor area.

3. Energy consumption

Greece is divided in four climatic zones, namely A, B, C and D,based on heating degree days (HDD for a base temperature of 18 ◦C):

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nd Buildings 43 (2011) 770–778

zone A (601–1100 HDD18 ◦C), zone B (1101–1600 HDD18 ◦C), zoneC (1601–2200 HDD18 ◦C) and zone D (2201–2620 HDD18 ◦C). Theinvestigated 11 typical bank branches are classified in four groupsaccording to the corresponding four climatic zones where they arelocated. The basic characteristics of each bank branch are presentedin Table 1. The code name of each bank branch first identifies theclimatic zone (A, B, C or D) followed by a sequential numerical value.

For zone A, monthly energy consumption data over a six yearperiod for 7 branches were collected and analyzed. The averagemonthly energy consumption was 25.6 kWh/m2, while the maxi-mum and minimum values were 39.3 kWh/m2 and 14.9 kWh/m2,respectively. On an annual basis, 50% of the branches have an energyconsumption lower than 300 kWh/m2, while for 34% of them itranges between 350 and 407 kWh/m2. The evolution of the aver-age annual energy consumption per unit floor area over the sixyear period is illustrated in Fig. 1 and reached 316 kWh/m2 (300 kgCO2/m2) in 2007.

Following an in-depth analysis of the data from the energyaudit and details of the installed E/M equipment for lighting,office and electronic equipment, and HVAC systems, it was pos-sible to estimate the energy consumption breakdown for thedifferent end-uses. The estimated annual energy consumption forHVAC ranged between 87.9 and 204.3 kWh/m2, while the averageinstalled power was 53.8 W/m2. On average, the HVAC contribu-tion to the total final energy consumption is 49.0% (of which 62.4%for cooling and 37.6% for heating), lighting follows with 32.5% (ofwhich 62% for indoor space lighting, 22% for the external marqueesign and 16% for security night lighting) and office and electronicequipment corresponds to 18.5%.

The analysis revealed that artificial lighting also contributessignificantly to the total energy consumption mainly due to theoperation of the large external marquee sign with the bank’s name.However, even excluding the use of this sign from the energybalance, the lighting energy consumption is higher compared toother office buildings. The estimated annual energy consumptionfor lighting ranged between 44.5 and 80.9 kWh/m2 for branch A-3,which is equipped with a largest external marquee sign (Table 1).The installed power for artificial lighting was estimated between28 W/m2 (for branch A-1) and 36 W/m2 (for branch A-3) or 21 W/m2

excluding the external marquee sign.The annual energy consumption for office and electronic equip-

ment ranged between 48.8 and 70.7 kWh/m2. The desktop personalcomputers and telecommunication equipment are the main end

uses, with an annual energy consumption ranging between 24.0and 31.6 kWh/m2. The automated teller machine (ATM) followswith an annual energy consumption between 12 kWh/m2 and23 kWh/m2 mainly due to its continuous operation throughout the

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G.N. Spyropoulos, C.A. Balaras / Energy and Buildings 43 (2011) 770–778 773

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ig. 2. Evolution of annual energy consumption (kWh/m2) over a six year period2002–2007) of 18 branches in climatic zone B. The numerical values indicate the

inimum, average (square) and maximum energy consumption.

ear. The average installed power for office and electronic equip-ent was 85.5 W/m2.For zone B, monthly energy consumption data over a six year

eriod for 18 branches were collected and analyzed. The averageonthly energy consumption was 29.6 kWh/m2, while the max-

mum and minimum values were 59 kWh/m2 and 12.9 kWh/m2,espectively. The evolution of the average annual energy consump-ion per unit floor area over the six year period is illustrated in Fig. 2nd reached 336 kWhm/m2 (319 kg CO2/m2) in 2007. On an annualasis, 33% of the branches have an energy consumption between00 and 300 kWh/m2, 22% between 300 and 350 kWh/m2, while for7% of them it ranges between 400 and 500 kWh/m2 (maximum63 kWh/m2).

The energy consumption breakdown for the different end-usesn the bank branches of zone B was based on an in depth analysisf 5 branches, where data was available. Again, the HVAC systems the major energy consumer. On average, the HVAC contributiono the total final energy consumption is 47.0% (of which 58.8% forooling and 41.2% for heating), lighting follows with 37.2% (of which0% for indoor space lighting, 49% for the external marquee sign and1% for security night lighting) and office and electronic equipmentorresponds to 15.8%.

The HVAC system covers both the cooling and the heating needsf each branch in the climatic zone B during the year. The estimatednnual energy consumption for HVAC ranged between 107.0 and50.6 kWh/m2, while the average installed power was 77.8 W/m2.he percentage for cooling to the total final energy consumptionanged between 18 and 31% and for heating 18–21%. The estimatednnual energy consumption for lighting ranged between 76.0 and18.7 kWh/m2 for branch B-4, which is equipped with the largestxternal marquee sign (Table 1) that represents 49% of the energyonsumption for lighting. The installed power for artificial lightingas estimated between 28.4 W/m2 (for branch B-2) to 51.9 W/m2

for branch B-4) or 31.5 W/m2 excluding the external marquee sign.The annual energy consumption for office and electronic equip-

ent ranged between 39.6 and 71.0 kWh/m2. The desktop personalomputers and telecommunication equipment have an annualnergy consumption between 14.6 and 24.3 kWh/m2 and the ATMsange between 6.8 and 11.0 kWh/m2. The installed power for officend electronic equipment ranged between 30.9 and 87 W/m2 withn average of 55.6 W/m2.

For zone C, monthly energy consumption data over a six yeareriod for 10 branches were collected and analyzed. All of the

ranches in this sample operate from 07:15 to 15:30, except forwo of them that have an extended daily operation for four moreours. The average monthly energy consumption was 33 kWh/m2,hile the maximum and minimum values were 45.2 kWh/m2 and

0.8 kWh/m2, respectively. The evolution of the average annual

Fig. 3. Evolution of annual energy consumption (kWh/m2) over a six year period(2002–2007) of 10 branches in climatic zone C. The numerical values indicate theminimum, average (square) and maximum energy consumption.

energy consumption per unit floor area over the six year period isillustrated in Fig. 3 and reached 391 kWhm/m2 (371 kg CO2/m2) in2007. On an annual basis, 40% of the branches have an energy con-sumption between 200 and 300 kWh/m2, while for 50% of them itranges between 400 and 500 kWh/m2.

On average, the HVAC contribution to the total final energyconsumption is 47.5% (of which 42.5% for cooling and 57.5% forheating), lighting follows with 34.6% (of which 51% for indoorspace lighting, 35% for the external marquee sign and 14% forsecurity night lighting) and office and electronic equipment cor-responds to 17.9%. The estimated annual energy consumption forHVAC ranged between 202.0 and 216.5 kWh/m2, while the averageinstalled power was 138 W/m2. The estimated annual energy con-sumption for lighting averaged 77.4 kWh/m2, while the installedpower for artificial lighting was estimated between 36.8 W/m2 (forbranch C-1) and 24 W/m2 (for branch C-2). Excluding the externalmarquee sign, the installed power for lighting drops to 26.4 and19.5 W/m2, respectively.

The annual energy consumption for office and electronic equip-ment ranged between 64.7 and 94.3 kWh/m2. The desktop personalcomputers and telecommunication equipment have an annualenergy consumption between 18.7 and 31.1 kWh/m2, with an aver-age installed power of 78.5 W/m2.

Zone D includes the coldest regions of northern Greece. Accord-ing to this survey, almost all branches located in these regions areequipped with oil-fired boilers in order to meet their heating needs.Consequently, electrical energy consumption is significantly lowerthan the corresponding values of branches located in the other cli-matic zones, for which all HVAC loads are satisfied by electricallydriven equipment, either central or local split unit heat pumps.However, heat pumps are also installed for cooling in summerand as a backup or supplementary heating systems in winter. Forzone D, monthly energy consumption data for 4 branches werecollected and analyzed. The average monthly energy consump-tion was 20.5 kWh/m2, while the maximum and minimum valueswere 35.5 kWh/m2 and 20.5 kWh/m2, respectively. Almost all ofthe branches have an annual electrical energy consumption ofabout 200 kWh/m2, with the exception of one branch that reached335 kWh/m2 (Fig. 4). Based on the sample of the 4 branches, theaverage CO2 emissions from electrical energy consumption wereestimated to 224 kg/m2.

The total energy consumption for heating and cooling was esti-mated to 131 kWh/m2 of which 36 kWh/m2 is from electricity and

2

103 kWh/m from heating oil (based on one branch where datafor heating energy was available). On average, the HVAC contribu-tion to the total final energy consumption is 44.2% (of which 12%for cooling and 88% for heating), lighting follows with 33.0% (ofwhich 63% for indoor space lighting, 26% for the external marquee

774 G.N. Spyropoulos, C.A. Balaras / Energy a

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176197

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208 214

273

335

148166 157 162

236

201

0

100

200

300

400

200720062005200420032002

kWhe /m 2

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ig. 4. Evolution of annual electrical energy consumption (kWh/m2) over a six yeareriod (2002–2007) of 4 branches in climatic zone D. The numerical values indicatehe minimum, average (square) and maximum energy consumption.

ign and 11% for security night lighting) and office and electronicquipment with 22.8%. The estimated annual energy consump-ion for lighting averaged 101 kWh/m2, while the installed poweror artificial lighting was estimated at 25.6 W/m2, which drops to1.0 W/m2 excluding the external marquee sign. The estimatednnual energy consumption for office and electronic equipmentas 70.4 kWh/m2. The desktop personal computers and telecom-unication equipment have an average annual electrical energy

onsumption of 18.9 kWh/m2, with an average installed power of4.2 W/m2.

Based on the available data from the investigated 11 typical bankranches and the calculated breakdown of energy consumption and

nstalled power for the different end-uses, revealed that the averagenergy use for lighting is: 19% of the final energy consumption forain building lighting, 11% for the external marquee sign and 5% for

ecurity night lighting. Finally, the breakdown of the various officend electronic equipment to the final energy consumption is: 9%or personal computers and telecommunication, 4% for ATMs, 1.2%or printers and copiers, 1.1% for standby, 1% for refrigerator andbout 0.7% all the other machines and other end-uses.

The energy intensity expressed as the ratio of the annual totalnergy consumption to the number of the employees (kWh/emp)or the different climatic zones, is illustrated in Fig. 5. Since theumber of staff in the investigated bank branches is not the samend thus the occupancy per unit floor area is not constant, it wasecessary that the calculations include only the branches where the

orresponding data was available and accurate. From a sample of 18ank branches the annual total energy consumption per employeearies between 4298 kWh/emp and 9650 kWh/emp, with an aver-ge value of 6993 kWh/emp.

5971

4298

7849

4874

8154 8371

9650

4874

6806 6782

8646

4874

0

2000

4000

6000

8000

10000

DCBA

Climatic Zone

kWh/emp

ig. 5. Energy intensity of the annual energy consumption per employeekWh/emp) in the audited bank branches for the different climatic zones.

nd Buildings 43 (2011) 770–778

4. Energy conservation measures

An analysis of the collected data has shown that significantenergy savings can be achieved in the bank branches by the adop-tion of various energy conservation measures (ECMs) for lightingand HVAC. Energy consumed by office equipment and appliancesis generally associated with the use of new energy efficient elec-tric and electronic devices. However, the energy audit revealedthat the vast majority of the bank branches are already equippedwith modern personal computers, printers and copiers. Moreover,it is difficult to reduce the standby energy consumption for prac-tical reasons; bank staff revealed that under heavy work pressureit is not practical to turn on/off the equipment during the work-ing hours. In addition, some office equipment like automated tellermachines (ATMs), faxes and digital video recorders DVRs have to bein standby mode all the time. Therefore, potential energy savingsoffice and electronic equipment were not considered.

The cost effectiveness analysis of the proposed ECMs is exam-ined in terms of the costs and the benefits that derive from theproposed measures when compared to the existing situation eachtime. This means that any additional expenses related to extralabour or materials required for the application of the measuresare not taken into account in the cost effectiveness analysis as theseexpenses may differ significantly from one branch to another. Forexample, double glass panes may not fit in all branch frames withsingle glass panes installed, meaning that lower or higher costs maybe involved each time. Such a financial analysis was not considered.

4.1. ECMs for lighting

Three different measures were examined. The first scenario wasa study of replacing the conventional starters (old type electromag-netic ballasts) in the luminaries with new HF electronic ballasts,along with the replacement of any incandescent lamps (75 W),where they exist, with more energy efficiency CFL lamps having thesame or better output (lm/W) [12]. The second scenario includedthe reduction of the operating hours of the external marquee sign.Finally, the third scenario included an investigation of the benefitsresulting from the reduction of the number of luminaries. The calcu-lations were performed by simulations using the DIALux advancedsoftware [13] for a typical branch.

4.1.1. Scenario A: replacement of the old conventional ignitionsystems with HF electronic ballasts and the incandescent lampswith CFL

The artificial lighting system in almost all the bank branches inthe country consists of lighting fixtures with conventional ballasts.Almost all branches in our investigation use typical 4 × 18 W T8and 2 × 26 W TCL lighting fixtures along with a small number ofincandescent lamps. A typical and representative sample of bankbranches was examined in this scenario in order to quantify theresults.

The average installed power of the lighting system was found tobe about 34 W/m2 which drops to 24.2 W/m2 if the external mar-quee sign is not used. The replacement of incandescent lamps andthe installation of electronic ballasts decreases the installed powerto 28.9 W/m2 and 19 W/m2 respectively, resulting to an averagereduction of 15% and 22%. The average energy savings and accord-ingly the CO2 emission reductions resulting from the installationof electronic ballasts is estimated at about 6.5% (min 4%, max 11%)and 12% (min 4%, max 19%) of the total final energy consump-

tion which accounts for an average energy savings of 22 kWh/m2

and 29 kWh/m2 with and without the use of the external marqueesign, respectively. Since there are some bank organizations with-out lighting external marquee signs consuming so much energy,the reader is advised to investigate the behavior of lighting system

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G.N. Spyropoulos, C.A. Balaras / En

n both cases (with and without the external marquee sign beingaken into account).

.1.2. Scenario B: reducing the operating hours of the externalarquee sign

The use of a large external marquee sign contributes signifi-antly to the lighting energy consumption as it operates on anverage of 10 h per day throughout the year. The specific sce-ario investigated the energy savings by reducing the operatingours to 8 h in winter (from 18:00 to 02:00) and 6.5 h in summerfrom 20:30 to 03:00). This measure could be acceptable from theank compared to the reduction of the operating hours of night

ighting that are bound to be on throughout the night for secu-ity reasons. An average reduction of 12% for the lighting energyemand and about 5% for the total final energy consumption cane achieved. The potential energy savings for the investigated1 typical bank branches average 16 kWh/m2 (average reduction

n CO2 emissions of about 14.8 kg/m2) and annual revenues ofbout 359 D .

.1.3. Scenario C: reducing the number of lighting fixturesA detailed simulation of a typical bank branch using the

dvanced lighting software DIALux revealed that there is a signifi-ant energy saving potential in lighting by reducing the number ofhe installed luminaries in the working areas by an average of 40%nd 36% of the two most commonly used types of luminaries inank branches. However, this is the maximum reduction that cane achieved in order to maintain a minimum illuminance of 400 luxn the working surface (Fig. 6). In practice, a safety percentage of10% should be considered. In our example, a representative samplef a typical bank branch of 150 m2 and 3.5 m height was consid-red. The array of the installed lighting fixtures was similar to thosencountered in most typical bank branches. The installed poweror the investigated 11 typical bank branches averages 34 W/m2

or 24.2 W/m2 if the external marquee sign is not considered) andfter reducing the number of lighting fixtures drops to 26.6 W/m2

or 17.6 W/m2 if the external marquee sign is not considered), buttill maintaining the appropriate illuminance levels. Based on theseesults, for the investigated 11 typical bank branches the average

nnual energy consumption for lighting with the existing installa-ions is 79.9 kWh/m2 (or 46.7 kWh/m2 if the external marquee signs not considered) and by reducing the number of luminaries caneach 63.5 kWh/m2 (or 31.7 kWh/m2 if the external marquee signs not considered). Thus, the average savings on the total energy

ig. 6. Simulation results of a typical bank branch with illuminance levels using a typicaluminaries (right).

nd Buildings 43 (2011) 770–778 775

consumption can reach a maximum of 7% (or 12% if the externalmarquee sign is not considered).

4.2. ECMs for HVAC

Energy consumption for HVAC dominates the total energy bal-ance in all bank branches with the exception of A-3 where thelarge length of the external marquee sign makes lighting the dom-inant energy consuming end-use. A reduction of the cooling andheating load and the associated energy savings is investigated intwo scenarios. The first scenario examines the adjustment of theindoor set point temperature in accordance to the recommendednational values for public buildings. The second scenario examinesthe potential reduction of the cooling and heating load by improv-ing the branches’ thermal envelope by replacing the single panewindows with insulated double glazing.

4.2.1. Scenario A: adjusting the indoor set point temperatureThe energy audit of the 11 typical branches revealed a wide

range of indoor set point temperatures ranging from 22 to 27 ◦C inwinter and 22–26 ◦C in summer. Significant energy savings couldbe achieved by adjusting the indoor set point temperature to therecommended indoor temperatures of 20 ◦C in winter and 26 ◦C insummer in accordance to the national legislation for public build-ings (Common Ministerial Decision OHJ �6/B/14826/17-6-2008).The calculations were performed using the simple heating degreeday (HDD) and cooling degree day (CDD) methods, where data wasavailable. Based on the results, by adjusting the indoor set pointtemperature to the recommended values the energy consumptionfor HVAC can be reduced by 45% on average, which means averagesavings on the total energy consumption of about 18% (56 kWh/m2)and annual revenues of about 900 D .

4.2.2. Scenario B: installing new insulated double glazingThe energy audit and the data collected from the archives of the

bank’s technical department show that a large number of the bankbranches are equipped with insulated double glazed facades. How-ever, the potential of energy conservation along with the associatedcost savings and the abatement of CO2 emissions was examined

for 3 branches of the sample that were identified to have non-insulated, single glazed facades. The thermal insulation of the wallswas not examined because of their small surface area compared tothe large transparent area. In addition, whenever there are opaqueelements in the external thermal envelope, the walls are usually

number and layout of installed luminaries (left) and after reducing the number of

776 G.N. Spyropoulos, C.A. Balaras / Energy and Buildings 43 (2011) 770–778

y = -0.0178x + 0.5392

y = 0.0178x + 0.2853

0%

10%

20%

30%

40%

50%

60%

8.5 9 9.5 10 10.5 11 11.5 12

)

Lighting Contribution to total Energy [%]HVAC Contribution to total Energy [%]

y = -0.0178x + 0.0651

y = 0.0178x - 0.0653

-10%

-8%

-6%

-4%

-2%

0%

2%

4%

6%

8%

10%

8.5 9 9.5 10 10.5 11 11.5 12

Equivalent operation hours of lighting (h)

HVAC Deviation from the initial value (48%)Lighting Deviation from the initial value (35%)

F quivalc

cisdeuasa1

otgbarSsbr

5

pbttna

Fp

Equivalent operation hours of lighting (h

ig. 7. Sensitivity analysis of the energy consumption breakdown by changing the eontributions from the initial values (right).

overed internally by large office closets and cabinets, thus reduc-ng large heat losses through the opaque elements. The U value foringle glazing is considered at 6.0 W/m2 K while for an insulatedouble glazing (5 mm, 10 mm air vacuum, 5 mm) the U value wasstimated at 3.2 W/m2 K. The calculations were again performedsing the simple HDD and CDD methods. Based on the results, theverage reduction in HVAC annual energy demand by replacingingle glazing with double glazing can reach 16% and the aver-ge savings on the total energy consumption can reach 5.7% or8 kWh/m2 with annual revenues of about 245 D .

The windows areas ranged from 46 to 63 m2 with an initial costf 1848–2536 D . The cost effectiveness evaluation was based onhe price difference between the two materials (no insulated singlelazing and insulated double glazing). The NPV calculations wereased on the current price of electricity at about 0.11 D /kWh with anverage annual increment of about 7%, with no loans so the discountate was taken equal to an average annual inflation of about 4%.ince the external facades of the bank branches have a long lifepan, the choice of installing insulated double glass panes woulde acceptable for the investigated case studies, with an internalate of return of 4.6–6.4%.

. Discussion

The calculated energy consumption indicators resulted fromrocessing data from actual electrical energy consumption of 40

ank branches over a period of 6 years. It is, therefore, reasonableo assume that the available data and results are representative forhe bank branches under investigation. However, since there wereo electricity meters for the different end uses (lighting, equipmentnd HVAC), the breakdown of consumption was estimated by pro-

y = -0.0411x + 0.6083

y = 0.0411x + 0.0411

0%

10%

20%

30%

40%

50%

60%

3.532.521.51Equivalent operation hours of equipment (h)

HVAC Contribution change to total Energy [%]Equipment Contribution to total Energy [%]

-1

-1

-

1

1

ig. 8. Sensitivity analysis of the energy consumption breakdown by changing the equivalercentage contributions from the initial values (right).

ent operating hours of lighting (left) and deviation of HVAC and lighting percentage

cessing the available data collected from the energy audits and thesurvey results from the occupant questionnaires, as well as fromthe interviews with the managers of each branch.

In order to investigate the possible error margins in the contri-bution of the various end uses to the final energy consumption, asensitivity analysis for the breakdown of energy consumption wasimplemented. The constants in this analysis are the final energyconsumption and the installed power of lighting and equipment forwhich it is believed that the possible errors are of minor importanceas they do not significantly influence the final results. However, thesignificant variables that were important in the calculation processare the operating hours of the lighting systems and the office andelectronic equipment.

To proceed in a sensitivity analysis of the contribution of thedifferent end uses to the final energy consumption, the case studyconsidered a typical branch with an average energy consumptiontaken as the average value of the sample included in this investi-gation. The percentage contribution of lighting and equipment arealso taken as the estimated average values of the sample. Accord-ingly, the equivalent hours of their operation were estimated foreach end-use separately taking into account the average installedpower of lighting and equipment and the average percentagesof their contribution to the total final consumption. Varying theequivalent operating hours of lighting and office and electronicequipment one can examine their impact on the final results andhow they alter the contribution of lighting, equipment and conse-

quently HVAC on the total energy consumption balance.

The average energy consumption of the sample was348 kWh/m2 while the corresponding average breakdown oflighting, equipment and HVAC to the final consumption were 35%,17% and 48%, respectively. The average installed power for lighting

y = -0.0411x + 0.1342

y = 0.0411x - 0.1344

5%

0%

5%

0%

5%

0%

5%

3.532.521.51

Equivalent operation hours of equipment (h)

HVAC Deviation from the initial value (48%)Equipment Deviation from the initial value (17%)

ent operating hours of office equipment (left) and deviation of HVAC and equipment

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G.N. Spyropoulos, C.A. Balaras / En

nd equipment was 34 W/m2 and 78 W/m2, while the equivalentperating hours for lighting and equipment were 10.1 h/day and.1 h/day, respectively. Fig. 7 illustrates how the contribution ofVAC and lighting affects the total energy consumption by consid-ring a range of possible values for the equivalent operating hoursor lighting. In this case the constant is the energy consumptionf office and electronic equipment, the independent variable ishe equivalent operating hours for lighting, and the dependableariables are the percentage contributions of HVAC and lighting tohe total energy consumption.

Similarly, Fig. 8 illustrates how the contribution of HVAC andffice and electronic equipment to the total energy consump-ion is affected by changing the equivalent operating hours of thequipment. The constant in this case is the energy consumptionor lighting. The independent variable is the equivalent operatingours of office and electronic equipment, while the dependableariables are the percentage contributions of HVAC and equipmento the total energy consumption.

The analysis revealed a maximum deviation of −4.7% to +6.0%or the contribution of lighting to the final energy consumption andmaximum deviation of +6.0 to −4.7 for the HVAC contribution to

he final energy consumption may occur when the equivalent oper-ting hours range between 8.5 h/day and 11.5 h/day (initial value0 h).

On the other hand, the average equivalent operating hours offfice and electronic equipment were estimated to be 2.1 h/day.ince, the installed power of office equipment is greater than thene for lighting, the preceding sensitivity analysis resulted to aaximum deviation of −9% to +11% for the contribution of equip-ent to the final energy consumption and a maximum deviation of

9% to −11% in the HVAC contribution to the final energy consump-ion, when the equivalent operating hours range between 1 h/daynd 3.5 h/day.

The energy consumption of the external marquee sign is anothermportant parameter that influences the results. Since the collectedata covers a depth of 6 years, an evaluation of the energy con-umption during this period was carried out. In almost all brancheshere is a significant increase of energy consumption from the year005 to 2006. This is the period when the new external marqueeigns were installed to all branches implementing new bank poli-ies. It is apparent that the external marquee sign plays a significantole in the energy consumption of the bank branches with an aver-ge contribution to the total energy consumption of 17%. This isn important finding if someone would like to examine in gen-ral the energy consumption in the banking sector especially forhese banks which have no external marquee signs installed. Thencrement of the energy consumption during the examined periodlso derives from the gradual increase of both the installed powernd the operation hours of equipment, lighting and HVAC unitsainly to meet the bank needs and achieve better conditions of

hermal comfort in many bank offices. Moreover, the expansion ofanks activities to new financial fields and modern products dur-

ng these years, resulted in the intensification of the working hoursnd accordingly in the increased use of the energy consumptionources as well.

. Conclusions

Energy consumption data from 39 Hellenic bank branches for aeriod of 6 years from all the climatic zones of the country were col-

ected and analyzed. An energy audit along with an in depth analysisor a representative sample of 11 typical bank branches was carriedut in order to investigate the energy consumption by the differentnd uses along with the potential of energy saving. Electricity is theain energy source for almost all branches using heat pumps for

nd Buildings 43 (2011) 770–778 777

HVAC, except for a small number of branches located at the north-ern part of the country (zone D) where oil fired boilers are used forheating.

Analysis of the available data revealed that the annual aver-age electricity consumption per air conditioned unit floor area is337 kWh/m2 (or 99 kWh/m3). Excluding the branches in zone Dwhere thermal energy is also used to cover heating loads, the annualaverage consumption is 348 kWh/m2 (101.6 kWh/m3). The aver-age total energy consumption (including thermal energy) is about346 kWh/m2 (102 kWh/m3). Based on the results from the sam-ple of the 11 typical branches the contribution of final end-uses tothe final energy consumption varies for lighting between 15% and60% with an average value of 35%, for office and electronic equip-ment between 13% and 22% with an average value of 17%, and forHVAC between 22% and 69% with an average value of 48%. It wasrevealed that the external marquee sign plays a significant role tothe total lighting load mainly because of its high installed powerand the long hours of operation. Reducing its operating hours mayresult to an average total energy saving of about 5%. Replacing bothconventional ballasts and the incandescent lamps with HF elec-tronic ballasts and CFL lamps could result to annual average totalenergy savings of about 22 kWh/m2 (or 6.7% savings). This corre-sponds to 11.7% if the external marquee sign is not considered inthe calculations. The evaluation of ECM’s for HVAC revealed thatregulating the indoor set point temperature to meet the recom-mended values, the total final energy consumption may be reducedfrom 15% to 25% which means an annual average reduction in thetotal energy consumption of about 56 kWh/m2. However, actualsavings will depend on the deviation of the actual settings fromthe recommended values. Replacing single glazing with insulateddouble glazing, the potential energy consumption savings average5.7%. However the cost effectiveness evaluation of this measure isstrongly dependent on many factors and may be a financial burden,especially compared against other energy conservation measures.

Acknowledgments

The research work was carried out by Mr. G. Spyropoulos, inpartial fulfilment of the requirements for an MSc in Energy at theDepartment of Mechanical Engineering, Technological EducationalInstitute of Pireaus, Athens, Greece and the School of Engineeringand Physical Sciences, Heriot-Watt University, Edinburgh, UK.

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[

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