Building and Environment 37 (2002) 575–578www.elsevier.com/locate/buildenv

Passive retro tting of o"ce buildings to improve their energyperformance and indoor environment: the OFFICE project

M. Santamouris∗, E. Dascalaki1

Group Building Environmental Studies, Department of Applied Physics, University of Athens, University Campus, Build. PHYS. -V,Athens GR157 84, Greece

Abstract

OFFICE was a research project, partly funded by the CEC, dealing with the passive retro tting of o"ce buildings to improve theirenergy performance and indoor working conditions. The project was coordinated by the University of Athens with the participation oforganizations and research institutes from eight European countries. The aim of the project was to develop global retro tting strategies,tools and design guidelines in order to promote successful and cost-e7ective implementation of passive solar and energy e"cient retro ttingmeasures to o"ce buildings. Within the frame of the project, 10 o"ce buildings located in di7erent climatic zones around Europe werestudied extensively. Energy audits and monitoring activities, speci c experiments as well as an assessment of the potential of proposedretro tting scenarios were performed for each building.The nal deliverables of the project include: (a) case studies presenting high-quality examples of representative retro tted o"ce buildings

in various parts of Europe; (b) a rating methodology classifying o"ce buildings according to their energy consumption, CO2 productionand indoor thermal and visual comfort; (c) an Atlas describing the technical and economical potential for energy conservation of selectedretro tting scenarios for de ned types of o"ce buildings in di7erent climatic zones of Europe and (d) Design Guidelines, performancecriteria and methodologies for best practice giving credit for renewable energy sources incorporated into o"ce buildings, all presented inthe form of a Handbook. Results from the assessment of the potential of various retro tting scenarios proposed for each case study areincluded in the Handbook in the form of brochures.This paper gives an analytical description of the activities carried out within the frame of the project and describes the resulting nal

deliverables. ? 2002 Elsevier Science Ltd. All rights reserved.

1. Introduction

Energy consumption in o"ce buildings is one of the high-est compared to the consumption of other building types.The annual energy consumption in o"ce buildings variesbetween 100 and 1000 kWh per square meter, depending ongeographic location, use and type of o"ce equipment, oper-ational schedules, type of envelope, use of HVAC systems,type of lighting, etc. Energy in o"ce buildings is mainlyconsumed for heating, cooling and lighting purposes, whilea signi cant portion is devoted to the consumption of o"ceequipment.

∗ Corresponding author.E-mail addresses: msantam@cc.uoa.gr (M. Santamouris), edasc@

dap.uoa.gr (E. Dascalaki).1 Current address: National Observatory of Athens, Institute for Envi-

ronmental Research and Sustainable Development, Group Energy Con-servation, I. Metaxa & Vas. Pavlou, Palaia Penteli, 152 36, Greece.

Retro tting of existing buildings presents by far thelargest potential for the incorporation of renewable energytechnologies and energy e"ciency measures into build-ings. Within many European countries there is considerablyhigher activity in retro tting and reusing buildings than inconstructing new ones. In the o"ce sector, retro tting ofthe post-war stock is seen in the property market as themajor area of activity for the next few years and thus theincorporation of renewable energy sources could be signif-icant. However, existing energy-related retro tting actionstend to almost completely neglect aspects related to passivesolar heating, daylighting and passive cooling of buildings.OFFICE was a research project partly funded by the

CEC dealing with the passive retro tting of o"ce build-ings to improve their energy performance and indoor work-ing conditions. The project was coordinated by the Univer-sity of Athens with the participation of organizations andresearch institutes from eight European countries, namely:

0360-1323/02/$ - see front matter ? 2002 Elsevier Science Ltd. All rights reserved.PII: S0360 -1323(02)00004 -5

576 M. Santamouris, E. Dascalaki / Building and Environment 37 (2002) 575–578

France, Italy, Germany, Switzerland, United Kingdom, Nor-way, Sweden and Denmark. The aim of the project wasto combine knowledge and expertise acquired through re-cent research actions on the development of passive so-lar heating, passive cooling and daylight techniques, withbest expertise on retro tting of o"ce buildings regardingarchitectural and engineering interventions.Application of energy conservation techniques, as well as

the use of solar and ambient alternative energy sources ino"ces, requires knowledge of the speci c energy charac-teristics of the buildings. The latter depends strongly on theconditions in the various climatic zones in Europe. In orderto investigate the possibilities of successful application ofretro tting interventions on buildings located in various cli-matic zones, a total of 10 buildings have been selected to bethoroughly investigated as case studies. The selection of thebuildings was based on the requirement to derive a group ofbuildings presenting the maximum possible variety of fea-tures related to the building typology, client requirements,construction details, location, thermal quality of the enve-lope, type of utilized energy sources and energy consump-tion. The list of the selected case studies covers a wide rangeof climatic zones around Europe, namely: North EuropeanCoastal (3 buildings), Mid European Coastal (1 building),Continental (4 buildings) and Southern Mediterranean (2buildings).Monitoring activities in the selected buildings included

thorough audits and recording of the indoor and outdoor en-vironmental conditions as well as of the consumption perenergy-end use. Retro tting studies involved an assessmentof the impact of proposed interventions on the energy per-formance of the buildings as well as an economic evalua-tion of each proposal. The results for each case study werepresented in the form of brochures presenting high-qualityexamples of representative retro tted o"ce buildings in var-ious parts of Europe.Data from energy audits in the above buildings, as well as

from the energy simulations were used in order to develop arating methodology classifying o"ce buildings according totheir energy consumption, CO2 production and indoor ther-mal and visual comfort. Simulations were also run in orderto derive the necessary information for an Atlas describingthe technical and economical potential for energy conser-vation of selected retro tting scenarios for de ned types ofo"ce buildings in di7erent climatic zones of Europe. Fi-nally, the main research results of the project in the form ofdesign guidelines, performance criteria and methodologiesfor best practice giving credit to renewable energy sourcesincorporated into o"ce buildings, were all included in theDesigner’s Handbook.

2. Monitoring of the case studies

The present state of each of the selected buildings wasthoroughly investigated using standardized questionnaires

for energy as well as indoor air quality auditing. In situinspections were carried out by a group of experts in orderto collect data regarding the architectural and engineeringcharacteristics as well as past energy consumption data forthe case studied buildings. Furthermore, the actual thermaland energy performance of the buildings was monitored foran 11-month period. During this period the following datawere recorded on an hourly basis:

• Climatic data from the nearest meteorological station:outdoor air temperature and humidity, global solarradiation, wind speed and direction.

• Indoor air temperature at representative locations on thetypical Ioor.

• One supply and one central exhaust air temperature.

Furthermore, the total energy consumption and its break-down for heating, cooling, lighting and equipment was mon-itored either using special watt-meters or by reading the me-ters already installed in the buildings. In the latter case therecorded values were monthly averages.Short-term monitoring activities involved extensive and

detailed hourly recording of indoor and outdoor tempera-ture and energy consumption for periods of 1 month duringsummer and winter. Speci cally, the following parameterswere monitored:Outdoor conditions (either at the location of the case study

or at the nearest meteorological station): air temperature andhumidity, wind speed and direction, direct and di7use solarradiation.

• Indoor air temperature at various locations in the building.• One central supply air temperature.• One exhaust air temperature.• Electrical consumption for the whole building.• Electrical consumption per energy-end use for the wholebuilding.

Additionally, speci c experiments were carried out in orderto assess the quality of the indoor environment regardinglighting and ventilation. The information collected duringthe monitoring activities and the audit was used in order tospot the problems in each building and specify the main ar-eas of intervention. Moreover, the data from the short-termmonitoring periods were used in order to develop more ac-curate computational models representing the actual state ofthe buildings as close as possible. These models were thebasis for the assessment of the retro tting interventions pro-posed for each case study.

3. Retro�tting scenarios

Based on the information collected during the energy au-dits as well as on the analysis of the data from the monitoringcampaigns in the investigated buildings, speci c retro tting

M. Santamouris, E. Dascalaki / Building and Environment 37 (2002) 575–578 577

interventions were proposed for each of them according totheir individual problems and requirements as they came outfrom the above analysis.E"cient application of energy retro tting measures in of-

ce buildings is mainly related to the application of systemsand techniques dealing with:

• The use of passive solar retro tting options.• The use of measures related to the rational use of energy.

The proposed interventions can be classi ed into the follow-ing categories:

• Actions aiming to improve the envelope of the buildingand introduce passive solar heating techniques and com-ponents.

• Actions aiming to result in a reduction or, wherever pos-sible, complete removal of the air conditioning.

• Actions aiming to improve lighting conditions, decreasethe energy consumption for arti cial lighting introducingdaylight.

• Actions aiming to improve the e"ciency of the selectedbuilding services, like HVAC system, production unitsand domestic hot water.

Actions aiming to improve the envelope of the buildingswere classi ed into the following major types:

• Reduction of the heat transmission through the buildingenvelope by insulating the external walls, roofs and Ioors.

• Reduction of the heat transmission through windows anddoors, by replacing frames in bad condition with newones as well as by replacing single with double glazings.

• Reduction of in ltration by sealing the window frames.• Integration of passive solar heating and daylight compo-nents.

• Improvement of natural ventilation and solar control.

Retro tting actions aiming to improve thermal comfort con-ditions during the summer period and decrease the coolingload of the buildings involve the following interventions:

• Interventions aiming to decrease solar and internal heatgains in the building. These include mainly use of moree"cient and appropriate solar control devices, as well asminimization of internal gains.

• Interventions aiming to modulate the solar and internalheat gains in the building. These involve the use of nightventilation as well as techniques taking advantage of thethermal mass of the building.

• Interventions aiming to dissipate the excess heat of thebuilding into a heat sink of a lower temperature like theambient air, the ground, the sky and the water. These in-volve the use of ceiling fans, natural ventilation strate-gies, economizer control techniques and use of evapora-tive cooling systems.

In order to investigate the e7ectiveness of various retro ttinginterventions on the improvement of the energy performanceof the investigated buildings, di7erent types of actions werestudied, ranging from simple to global approaches. Regard-ing the retro tting interventions considered for each build-ing, three types can be considered:

• Measures, involving simple actions a7ecting only one ofthe above categories.

• Scenarios, involving combined actions a7ecting only oneof the above categories.

• Packages, involving integrated solutions involving themost e"cient combination of actions on all of the abovecategories.

The retro tting studies for each building involved an as-sessment of the proposed measures, scenarios and packagesfrom both energy conservation and economy related aspects.The impact of each action on the energy performance ofthe buildings was assessed through energy simulations usingcomputer models ‘calibrated’, so as to describe the actualstate of each building as close as possible. The ‘ ne tuning’of the models was based on the data collected during theshort-term monitoring periods. The economic feasibility ofeach of the proposed actions was expressed in terms of thepay back as well as amortization period.

4. Rating methodology

Two types of methodologies were considered in theframework of the OFFICE project:

(a) Methodologies classifying buildings according to theirenergy consumption for all cases where only energy dataare available.

(b) Methodologies classifying buildings according to theirenergy consumption and indoor environmental qualityinvolving thermal comfort, visual comfort and indoorair quality.

The aim of the new labelling scheme is to improve indoorenvironment together with a reduction of the energy con-sumption and environmental impact, while other existingrating methodologies mainly focus on energy consumptiononly. Three techniques have been considered.

(A) A ranking methodology based on a multi-criteria anal-ysis technique to rank buildings taking account of sev-eral criteria related to:• Energy use for heating, cooling, lighting and otherappliances.

• Impact on environment (greenhouse e7ect, acidity po-tential, etc.)

• Indoor environment quality.

578 M. Santamouris, E. Dascalaki / Building and Environment 37 (2002) 575–578

The methodology is based on a total of 40 parameters. Theranking methods can be used for:

• ranking buildings of a given building stock accordingto several criteria, thus helping in the determination ofpriorities for retro t;

• ranking various alternative retro t scenarios, helping thechoice of “the best” one, not only from one point of view,but for a combination of criteria;

• determining if a retro t building is actually better thanthe original one, from all the considered points of view.

(B) Energy rating methodologies, based either on:• the objective de nition of disjoint classes for energyconsumption from statistical data, and crisp ratingthe considered building into one of these classes; or

• using the Fuzzy C-means algorithm to de ne, fromstatistical data, building clusters with respect to en-ergy consumption and location of the consideredbuilding into one of these clusters. The clusters arepositioned in a two- or three-dimensional space,each coordinate being a parameter characterizing thebuilding (e.g. energy for heating, for cooling andfor other appliances).

(C) A relative classi cation technique, based on the use ofprincipal component analysis to rank many buildingsfrom a given building stock according to several cri-teria related to energy and environment (internal andexternal). The methodology uses as classi cation pa-rameters quantitative (energy) and qualitative param-eters (comfort, daylight, indoor quality).

The rating methodologies were used to compare a givenbuilding with standards or with an average situation, and todetermine whether the considered building complies withregulations.

5. Atlas

An investigation of the energy conservation potential ofselected retro tting interventions on European o"ce build-ings was carried out in the framework of the Design Guide-lines task. For this purpose, the energy performance of vari-ous retro tting scenarios and global retro tting actions wasassessed for di7erent o"ce building types. Based on a ty-pology study [1] carried out within the OFFICE project, theEuropean o"ce building stock was considered to include ve main building types according to four criteria, namely:

degree of exposure, thermal mass, skin dependence and in-ternal structure. Accordingly, the following building typeswere thoroughly studied:

• Free standing=Heavy=Core dependent=Open plan.• Enclosed=Heavy=Skin dependent=Cellular.• Free standing=Heavy=Skin dependent=Cellular.• Free standing=Light=Skin dependent=Open plan.• Enclosed=Light=Skin dependent=Cellular.

The impact of the climatic variations on the e7ectivenessof the above retro tting interventions was assessed throughenergy simulations using climatic data from 10 locations inthe four main European climatic regions, namely:

• South Mediterranean• Continental• Mid Coastal• North Coastal

Analysis of the results revealed the main trends in the be-havior of buildings belonging in each type. Results are givenin the form of a software developed in the highly illustrativeenvironment of MATLAB and a report [2].

6. Handbook

The Handbook aims to provide speci c guidance to de-signers who wish to reduce energy use in existing o"cesor refurbish an o"ce block using the latest energy savingand environmental friendly techniques. The main researchresults from the OFFICE project are given in the form ofguidelines together with the brochures from the 10 case stud-ies standing as examples of best practice retro tting of o"cebuildings.

Acknowledgements

The authors would like to acknowledge the EuropeanCommission for the nancial support of the OFFICE project.

References

[1] Tombazis A, Vratsanos N, editors. O"ce building typologies inEurope. Report No OF-1, OFFICE programme, JOR3-CT96-0034.

[2] Dascalaki E, editor. ATLAS on the potential of retro tting scenariosfor o"ces. Final report, OFFICE programme, JOR3-CT96-0034.