01-Existing Building Retrofits Methodology and State-Of-The-Ar

Energy and Buildings 55 (2012) 889902

Contents lists available at SciVerse ScienceDirect

Energy and Buildings

j ourna l ho me p age: www.elsev ier .com/ locate /enbui ld

Review

Existing building retrots: Methodology and state-of-the-art

Zhenjun Sustainable Bu

a r t i c l

Article history:Received 15 JuReceived in reAccepted 15 A

Keywords:Existing buildiSystematic apRetrot activitEnergy efcienState-of-the-a

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8892. Gener

2.1. 2.2. 2.3.

3. Sustai3.1. 3.2. 3.3. 3.4. 3.5. 3.6. 3.7.

4. Resea4.1. 4.2. 4.3. 4.4.

5. ConclRefer

CorresponE-mail add

0378-7788/$ http://dx.doi.oic building retrot problem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 889Key phases in a sustainable building retrot programme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 889Key elements affecting building retrots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 890Other important issues related to building retrots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 891

nable building retrots methodology and strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 891A systematic approach for sustainable building retrots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 891Building energy auditing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 891Building performance assessment and diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 891Quantication of buildings energy conservation benets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893Economic analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893Risk assessment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 894Measurement and verication of energy savings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 894

rch and application of retrot technologies for building performance enhancement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 894Building retrot technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 894Retrot studies on commercial ofce buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 895Retrot studies on residential buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 896Research studies on other types of buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 899

usions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 899ences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 900

ding author. Tel.: +61 02 4221 4143.ress: [email protected] (Z. Ma).

see front matter 2012 Elsevier B.V. All rights reserved.rg/10.1016/j.enbuild.2012.08.018Ma , Paul Cooper, Daniel Daly, Laia Ledoildings Research Centre (SBRC), Faculty of Engineering, University of Wollongong, New South Wales (NSW) 2522, Australia

e i n f o

ne 2012vised form 8 August 2012ugust 2012

ngsproachiescyrt

a b s t r a c t

Retrotting of existing buildings offers signicant opportunities for reducing global energy consumptionand greenhouse gas emissions. This is being considered as one of main approaches to achieving sus-tainability in the built environment at relatively low cost and high uptake rates. Although there are awide range of retrot technologies readily available, methods to identify the most cost-effective retrotmeasures for particular projects is still a major technical challenge. This paper provides a systematicapproach to proper selection and identication of the best retrot options for existing buildings. Thegeneric building retrot problem and key issues that are involved in building retrot investment deci-sions are presented. Major retrot activities are also briey discussed, such as energy auditing, buildingperformance assessment, quantication of energy benets, economic analysis, risk assessment, and mea-surement and verication (M&V) of energy savings, all of which are essential to the success of a buildingretrot project. An overview of the research and development as well as application of the retrot tech-nologies in existing buildings is also provided. The aim of this work is to provide building researchers andpractitioners with a better understanding of how to effectively conduct a building retrot to promoteenergy conservation and sustainability.

2012 Elsevier B.V. All rights reserved.

890 Z. Ma et al. / Energy and Buildings 55 (2012) 889902

1. Introduction

The construction of buildings and their operation contributeto a large proportion of total energy end-use worldwide [13]. Inthe buildingwhile the reonly aroundment of entimely redumental sust

During torganisatioimprovemeUnited Stattance to suCommerciainto effect Australias lciency info20092010million to pincrease thmade a signof 7.0 milliemissions blaunched aexisting buon energy Annex 50 dential builretrottingbuilding renancial asof energy e

At the scarried outopportunitiing buildingin existing retrottingrequired toing retrottapproachessumption a

Retrottopportunitimany uncehuman behwhich direhence the sings are higdifferent iminteractionsnologies beand systemsustainablenancial limand interruing ownersnancial suof split inretrot genows primabuilding offincreased ster thermal

security and corporate social responsibility, reduce exposure toenergy price volatility, create job opportunities and make build-ings more liveable [26,27]. Ernst and Young [26] has estimated thatin New South Wales (Australia) between $25 million and $99 mil-

tota the ada

at arhichlar py contics, and egle cl solergynmens papvelologiem anve res en

anal sav.

eric

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y ph

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rstle ren ber toin cos to s

respt.

secoent

g enwith

conloyeanc

sticsl schion. ent, res

thirapprsessm sector, most energy is consumed by existing buildingsplacement rate of existing buildings by the new-build is

1.03.0% per annum [47]. Therefore, rapid enhance-ergy efciency in existing buildings is essential for action in global energy use and promotion of environ-ainability.he last decade, many governments and internationalns have put signicant effort towards energy efciencynt in existing buildings. The federal government of thees, for example, has provided signicant nancial assis-pport existing building retrots [8,9]. In Australia, thel Building Disclosure (CBD) programme, which cameon the 1st November 2010, requires the owners ofarge commercial ofce buildings to provide energy ef-rmation to potential buyers or lessees [10]. In their

state budget, the Queensland government invested $8.0rogressively retrot existing government buildings toeir energy efciency [11]. In 2010, the UK governmenticant commitment to upgrade the energy efciency

on British homes by 2020 aiming at reducing carbony 29% [12]. The International Energy Agency (IEA) has

set of Annex projects to promote energy efciency ofildings, such as: Annex 46 Holistic assessment toolkitefcient retrot measures for government buildings;Prefabricated systems for low energy renovation of resi-dings; Annex 55 Reliability of energy efcient building; and Annex 56 Energy & greenhouse gas optimisednovation [13]. These efforts provided policy guidance,sistance and technical support for the implementationfciency measures in existing buildings.ame time, a signicant amount of research has been

to develop and investigate different energy efciencyes in order to improve energy performance of exist-s [1,1423]. The results have showed that energy usebuildings can be reduced signicantly through proper

or refurbishment [1723], which is described as work upgrade an aged or deteriorated building [14]. Build-ing or refurbishment is being considered as one of main

to realistically achieving reduced building energy con-nd greenhouse gas emissions.ing of existing buildings has many challenges andes. The main challenge encountered is that there arertainties, such as climate change, services change,aviour change, government policy change, etc., all ofctly affect the selection of retrot technologies anduccess of a retrot project. The subsystems in build-hly interactive. Different retrot measures may havepacts on associated building sub-systems due to these, which results that the selection of the retrot tech-comes very complex. Dealing with these uncertainties

interactions is a considerable technical challenge in any building retrot project. Other challenges may includeitations and barriers, perceived long payback periods,

ptions to operations [24,25]. The willingness of build- to pay for retrots is another challenge if there is nopport from the government, particularly since the issuecentives is often a key factor where the cost of theerally falls to a building owner whereas the benet oftenrily to the tenants. On the other hand, retrotting of aers great opportunities for improved energy efciency,taff productivity, reduced maintenance costs and bet-

comfort. It may also help to improve a nations energy

lion inwithin

Nowgies thas to wparticuto manacteristypes the sinoptimanon-enenviro

Thiand detechnoprobleeffectisuch anomicenergycussed

2. Gen

Theimplemto achifactorya givening theconsid

2.1. Ke

Themajor retroneed toavailabcan thein ordethe maownerto takeretro

Theassessmbuildinareas energyis empperformDiagnocontrooperatassessmand 3.3

Theusing risk asl economic activity could be realised by the year 2020building energy efciency market.ys, there is a great number of building retrot technolo-e readily available in the market. However, the decision

retrot technology (or measure) should be used for aroject is a multi-objective optimisation problem subjectstraints and limitations, such as specic building char-

total budget available, project target, building servicesfciency, building fabric, etc. Financial benet is notriteria for the selection of the retrot technologies. Theution is a trade-off among a range of energy related and

related factors, such as energy, economic, technical,tal, regulations, social, etc.er aims at providing an overview of recent researchpment in this eld as well as the application of retrots to existing buildings. The generic building retrotd a systematic approach to proper selection of costtrot measures are presented. Key retrot activities,ergy auditing, building performance assessment, eco-ysis, risk assessment, measurement and verication ofings, etc., involved in a building retrot, are also dis-

building retrot problem

lding retrot optimisation problem is to determine, and apply the most cost effective retrot technologiesnhanced energy performance while maintaining satis-ice levels and acceptable indoor thermal comfort, underof operating constraints. The following issues address-ure of a building retrot problem should be carefully

in a building retrot project.

ases in a sustainable building retrot programme

all process of a building retrot can be divided into vees (Fig. 1). The rst phase is the project setup and pre-vey. In this phase the building owners, or their agents,

dene the scope of the work and set project targets. Thesources to frame the budget and programme of work

determined. A pre-retrot survey may also be required better understand building operational problems andncerns of occupants. It is common practice for buildingelect an experienced Energy Services Company (ESCO)onsibility for planning and implementing the building

nd phase comprises an energy audit and performance (and diagnostics). Energy auditing is used to analyseergy data, understand building energy use, identify

energy wastes, and propose no cost and low costservation measures (ECMs). Performance assessmentd to benchmark building energy use by using selectede indicators or using green building rating systems.

can be used to identify inefcient equipment, improperemes and any malfunctions happened in the buildingDetails of building energy auditing and performance

(and diagnostics) are briey presented in Sections 3.2pectively.d phase is the identication of retrot options. Byopriate energy models, economic analysis tools andent methods, the performance of a range of retrot

Z. Ma et al. / Energy and Buildings 55 (2012) 889902 891

retrot programme.

alternativescan then benon-energyno cost andthe energy ysis and risrespectively

The fourThe selecteand commimeasures toin an optimof some retto the build

The naOnce the redard M&V mA post occuthe buildingoverall retroSection 3.7.

2.2. Key ele

The succissues. Fig. 2on buildingresources ainformation

Policies set minimuexisting buisubsidies tothe requireenergy retrgrammes avreview of hcal strategiehas been prcies, such a(EPBD), US [24].

Client reand goals, ashould be uare quite coinvestmentdred rms, rms decis

re a large number of factors involved and the most widelyecision-making rule is the payback period. A study by Ala-] showed that non-retrotting ECMs with no or low capitalent only saved 6.5% of building annual energy consump-

hile the retrotting ECMs measures with signicant capitalent can save up to 49.3% of annual energy consumption.

rot technologies are energy conservation measures (ECMs)o promote building energy efciency and sustainability.t technologies range from the use of energy efcient equip-advanced controls and renewable energy systems to thes of energy consumption patterns, and the application ofed heating and cooling technologies. Retrot measures

be considered in their order of economic payback, complex- ease

effeg-spe, siz

souetc. F

be d.Fig. 1. Key phases in a sustainable building

can be assessed quantitatively. The retrot alternatives prioritised based on the relevant energy-related and-related factors. It is worthwhile to note that a range of

low cost ECMs that might have been identied duringauditing. Details of energy simulation, economic anal-k assessment are presented in Sections 3.4, 3.5 and 3.6,.th phase is site implementation and commissioning.d retrot measures will be implemented on-site. Testssioning (T&C) is then employed to tune the retrot

ensure the building and its services systems operateal manner. It is worth noting that the implementationrot measures may necessitate signicant interruptioning and occupants operations.l phase is validation and verication of energy savings.trot measures are implemented and well tuned, stan-ethods [28,29] can be used to verify energy savings.pancy survey is also needed to understand whether

occupants and building owners are satised with thet result. Details of the M&V methods are presented in

ments affecting building retrots

ess of a building retrot programme depends on many shows the key elements that have signicant impacts

retrots, including policies and regulations, clientnd expectations, retrot technologies, building specic, human factors and other uncertainty factors.and regulations are energy efciency standards, whichm energy efciency requirements for retrotting ofldings. Governments may provide nancial support and

assist building owners and developers in achievingd energy performance targets through implementingot measures. Often the range of government pro-ailable is complex, even within a single jurisdiction. A

there aused djmi [32investmtion, winvestm

Retused tRetroment, changeadvancshouldity and

Thebuildining typenergytems, shouldmationow the renovation policies are changing and the politi-s that have guided the promotion of housing renovationovided by Baek and Park [30]. A summary of public poli-s European Energy Performance of Buildings DirectiveStandard 189.1, on green buildings can be found in Ref.

sources and expectations determine the project targetsnd thus determine which kind of retrot technologiessed. Since investment decisions for energy efciencymplex, it is always difcult for clients to decide whether

in retrots is worthwhile. Based on a survey of one hun-Harris et al. [31] identied the factors that inuence aion on investment in energy efciency. It was found that of implementation [33].ctiveness of a building retrot is also dependent onecic information, such as geographic location, build-e, age, occupancy schedule, operation and maintenance,rces, utility rate structure, building fabric, services sys-or a particular project, the optimal retrot solutionsetermined by taking into account building specic infor-Fig. 2. Key elements inuencing building retrots.


Human factors are other important elements that affect thesuccess of building retrots. Human factors may include comfortrequirements, occupancy regimes, management and maintenance,activity, and access to controls [33]. A survey by Owens and Wil-hite [34] shcounties caYohanis [35behaviour studied thepant behavNetherlandbehaviour senergy use showed thaand comforsavings are

As preseuncertaintyessential toing energy

2.3. Other i

The folloretrot pro

Each buildmeasuresanother b

The beneby using edifferent ECM is remance an

The selectlem. Multa wide vaof compliweightingthe optim

The optimbased apapproachused to esenergy safree approExpert syof an expdatabase of experti

In the mused to seoptimisatgenetic aannealingretrot so

3. Sustainastrategies

3.1. A syste

Fig. 3 illmining andbuildings. I

requiring minor modications. The overall retrot strategy consistsof two parts: (a) strategic planning and models/tools selection and(b) major retrot activities in the whole building retrot process.The strategic planning and models/tools selection are to provide

ary irategies pr

thing sy

the ure r. Thts tha

ildin

rgy aed asts, fan bntianergding rgy astralto th: enis [40evel

and andre arf enal. [4ent

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sting in u]. Thel systermmenappecan aerciated ee useionalhe la

asset thas LEEowed that 1020% of domestic energy use in the Nordicn be saved from occupant behaviour changes alone.] investigated householders awareness, attitudes andin relation to domestic energy use. Santin et al. [36]

importance of household characteristics and occu-iour on energy use for space and water heating in thes. The results showed that occupant characteristics andignicantly affect building energy use. The impact onfor heating is around 4.2%, for example. These studiest the changes of occupant behaviour, occupant controlst range can lead to signicant energy savings. The energy

often achieved with no or low capital investment.nted earlier, building retrots are also affected by many

factors. A good estimation of uncertainty factors is help select the best retrot options to maximise build-efciency during its whole life span.

mportant issues related to building retrots

wing issues also address the nature of the buildingblem.

ing is unique with different characteristics. The retrot used in one building may not be suitable for use inuilding.t of using multiple ECMs is not the sum of the benetsach individual ECM due to the interactive nature amongbuilding subsystems and different ECMs. Whether ancommended depends on its thermodynamic perfor-d the physical interactions among different ECMs [37].ion of the ECMs is a multi-objective optimisation prob-i-objective optimisation is a scientic area that offersriety of methods with great potential for the solutioncated decision problems [38]. The criteria selection and

factor assignments are essential in the formulation ofisation problem for building retrots.isation problem can be developed by using model-proach or model-free approach. In model-based, energy simulation models (or tools) are commonlytimate energy savings of different ECMs. The analysis ofvings should recognise the modelling mismatch. Model-ach does not require a model of the targeted system.stem is a typical model-free approach. The applicationert system is affected by the richness of the knowledgesince the rules used are static and outside of the domainse, threatening signicant errors [39].odel-based approach, the optimisation technique isarch for the optimal solutions. For the multi-objectiveion problem, global optimisation techniques, such aslgorithm (GA), branch and bound (B&B), simulated

(SA), etc., can be used to search for globally optimallutions.

ble building retrots methodology and

matic approach for sustainable building retrots

ustrates a systematic approach to identifying, deter- implementing the best retrot measures for existingt could be used for retrotting any type of buildings

necessThis stactivit

Onebuildindata into ensmanneprojec

3.2. Bu

Enea denand cosures can essewith ein buil

Eneand Aued inLevel 2analysaudit ldetailstargets

Thetance oXu et equipmetc. Siperformretrocollectpredicthe parthe use

Comcomprenergypossibassist i

3.3. Bu

Exichange[47,48overalable thDepartmay hfaults commpresentics aroperat

In tmancethe facsuch anformation and resource support for retrot activities.y was developed based on the retrot phases and keyesented in Section 2.1.g needs to be addressed is that regular monitoring ofstem operation and frequent review of the operationalpersistence period (i.e. post-retrot period) are neededthat the system continues to operate in an efcientis is essentially important for performance contractingt need to continuously determine energy savings.

g energy auditing

udits (and surveys) are investigations of energy use inrea or site. They enable an identication of energy userom which energy cost and consumption control mea-e implemented and reviewed [40]. Energy audits playl role in an energy retrot programme to identify areasy saving potential and provide the information neededperformance assessment.udits vary in range and depth. As per ASHRAE Handbookian/New Zealand Standard, energy audits can be classi-ree levels, including Level 1: walk through assessment,ergy survey and analysis, and Level 3: detailed energy,41]. For a particular project, the appropriate energycan be selected by taking into account the amount of

level of accuracy required, budget available, project goals dened, and scope of work covered.e a number of studies that have highlighted the impor-ergy audits in sustainable building retrots [32,4247].2] pointed out that retrot technologies reect new, new energy resources, new energy audit technologies,nergy audits can help better understand the energye of a building and its services systems, the potentialortunities can be identied based on the informationuring the energy audit [32,4345]. In order to reliablyrgy savings from a set of proposed retrot measures,ters of the simulation models can be calibrated throughnergy audit data [46,47].cial buildings nowadays are mostly equipped withsive building automation systems (BASs) and buildingagement and control systems (EMCSs) that allow theof using BAS data and EMCS data in energy audits tontifying energy conservation opportunities.

g performance assessment and diagnostics

buildings tend to undergo performance degradations,se, and unexpected faults or malfunctions over timese events often result in signicant deterioration of theem performance, inefcient operation and unaccept-al comfort conditions. A study supported by the U.S.t of Energy identied more than 100 types of faults thatn in commercial building services systems and theseccount for 211% of the total energy consumption ofl buildings [49]. In a sustainable building retrot, asarlier, building performance assessment and diagnos-d to benchmark building energy use, identify system

problems, and nd energy conservation opportunities.st two decades, the development of building perfor-ssment tools has been very active. This is reected int a set of building rating tools are in the public domain,D, BREEAM, CASBEE, HKBEAM, GBTool, E-top, Green


Fig. 3. A systematic approach for sustainable building retrots.


Star, NABERS, etc. These rating tools provide a framework on how toevaluate and improve building energy and environmental perfor-mance. Although these rating tools vary in scope, criteria, structureand format, the rating process is usually conducted via benchmark-ing the asseand qualita[50]. Throuthe buildingbuilding cabuilding rat

There isdevelopmegies for buinstance, Riating buildiapproach rebased apprmeasuremedures. Poelsoftware thexisting dwmodel idenment of occtypology caformance oenergy advof buildingeasy-to-useconditioninCaccavelli evaluate thoration, funenvironmendiagnostics

For a pament methaccount thcompanies,

3.4. Quanti

Reliableessential infor prioritisretrot meation and mo

There arpackages, suSIM+, TRNScharacteristsures. For ininvestigate ery school iAscione et afor ofce buanu [61] embuilding rebuilding en

Besides bsimulation energy perrange frombox modelsmatical moof technoloexplicitly al

combinations of alternative retrot actions. Rysanek and Choud-hary [37] presented the development of a new transient buildingphysics and energy supply systems modelling process for simulat-ing the effect of large sets of building retrot options. The strength

modith rudy,echnis. An

pred et ation e mo

the m anares.ldingergyting

buileme

stuial roiffer

with para

It is ws areortanted b

onom

seleent

the mparicationd coariet

ecosuch l ratek pess thly, thdvanvenere ar

efcmostamononomthe naklion mptio

on most eyed f

anags. Honomg re

resu assessed building against a set of prescribed quantitativetive performance indicators (PIs) of diverse objectivesgh examination of the difference between the PIs of

assessed and the targeted PIs, the performance of then be quantied. A detailed comparison of a variety ofing tools can be found in Refs. [51,52].

a wide range of research specically focused on thent and application of appropriate models and strate-ilding performance assessment and diagnostics. Forchalet et al. [53] summarised three approaches to evalu-ng energy performance, including computational-basedlying on input data from energy audits, performance-oach through analysis of building utility bills, andnt-based approach with in situ measurement proce-

et al. [54] provided an overview of the methods andat can be used for energy performance assessment ofellings. Mejri et al. [55] presented the application oftication techniques for energy performance assess-upied buildings. Dascalaki et al. [56] stated that buildingn be adopted as a tool for estimating the energy per-f residential buildings. It can be employed for initialice activities to give building owners a quick overview

energy performance. Song et al. [57] developed an tool for fault detection and diagnosis of building air-g systems. In the decision-making tool presented byand Gugerli [58], a diagnosis package was used toe general state of ofce buildings with respect to deteri-ctional obsolescence, energy consumption and indoortal quality. Details of the methods used for building

can be found in Ref. [59].rticular project, the appropriate performance assess-od and diagnostics tool can be selected by taking intoe client requirements, experience of energy services

major retrot focus, etc.

cation of buildings energy conservation benets

estimation and quantication of energy benets are a sustainable building retrot decision-support systemation of retrot measures. The performance of differentsures is commonly evaluated through energy simula-delling.e a number of whole-of-building energy simulationch as EnergyPlus, eQUEST, DOE-2, ESP-r, BLAST, HVAC-

YS, etc., that can be used to simulate the thermodynamicics and energy performance of different retrot mea-stance, TRNSYS was used by Santamouris et al. [60] tothe energy saving potential of green roofs in a nurs-n Greece. EnergyPlus was used by Chidiac et al. [18] andl. [46] to simulate the effectiveness of retrot measuresildings and historical buildings, respectively. Zmeure-ployed DOE-2 to estimate the energy savings due to

trots. A detailed comparison of the capabilities of 20ergy simulation packages can be found in Ref. [62].uilding energy simulation packages, a variety of energymodels have been developed and used to estimateformance of different retrot measures. The models

detailed physical models to grey box models and black. Asadi et al. [1] developed a multi-objective mathe-del to provide the decision support in the evaluationgy choices for building retrot strategies. This modellows for the simultaneous consideration of all available

of thistexts wcase stelling tanalys[64] toRafterycalibraimprovtion inused tomeasu

Buithe enof exisparingimprov

TheessentSince dbilitiesand itsmates.modelis impgenera

3.5. Ec

Theinvestmtion ofthe coan indcient a

A vate thethem, overalpaybacto assenativeother aeffecti

Theenergyis the ment the ecuse of by Kayinsulatconsummisatimost cemploDPP, tobuildinand ecmentin

Thenomicel is in its applicability to real retrot investment con-espect to decision-making. In the context of a particular

Murray et al. [63] stated that a static simulation mod-ique is sufcient as an underlying technique for retrot

articial neural network (ANN) was used by Yalcintasict the energy savings for building equipment retrots.l. [65] presented an evidence-based methodology forof whole building energy models. This methodology candel accuracy through using building veriable informa-odel calibration process. The calibrated models can be

lyse and estimate the energy savings of different retrot

information modelling (BIM) can also be used to predict performance of retrot measures by creating modelsbuildings, proposing alternatives, analysing and com-ding performance for these alternatives and modellingnts [24].dies above showed that energy simulation plays anle in analysing the performance of retrot measures.ent models (and tools) offer different prediction relia-

different uncertainties, the model (and tool) selectionmeter identication are essential to ensure reliable esti-orthwhile to note that simulation packages and energy

generally developed based on certain assumptions. Itt for users to recognise the simulation uncertaintiesy such assumptions.

ic analysis

ction of retrot measures is a trade-off between capital and benets that can be achieved due to implementa-retrot measures. Economic analysis, which facilitatesison among alternative retrot measures, can providen of whether the retrot alternatives are energy ef-st-effective.

y of economic analysis methods can be used to evalu-nomic viability of building retrot measures. Some ofas net present value (NPV), internal rate of return (IRR),

of return (ORR), benet-cost ratio (BCR), discountedriod (DPP), and simple payback period (SPP), can be usede economic feasibility of a single retrot measure. Alter-e life cycle cost method, the levelized cost of energy andced analysis methods can be used to evaluate the cost

ss of multiple retrot alternatives [66,67].e many studies related to economic analysis of buildingient measures. Remer and Nieto [68] identied that NPV

typical technique for optimal building energy assess-g 25 techniques. Verbeeck and Hens [69] discussedic viability of different retrot measures through the

NPV method. The life cycle cost assessment was usedi [70] to determine the optimum thickness of thermalaterial in a building envelope and its effect on energyn. Peterson and Svendsen [71] used an economic opti-ethod derived from the NPV method to determine theffective energy efciency measures. Nikolaidis et al. [72]our economic analysis methods, i.e. NPV, IRR, BCR, andlyse energy saving measures in common types of Greekuber et al. [73] studied the weights of social, culturalical factors in the decision-making process for imple-

trots measures in domestic buildings.lts from these studies have demonstrated that eco-

ssment techniques allow for selection of the most cost


effective retrot measures. This in turns aids the decision supportprocess in making an optimal design of building retrots.

3.6. Risk assessment

Risk asseitative valuthreat [74].mation aboprobability estimate [6many uncetion, energyenergy conetc. These uretrots is hto provide dselect and d

While thmethods aare probabbased risk meanvariadiscount raCarlo simuanalysis [66

There arrisk assessminstance, Mmining theby taking incycle cost aprobabilistiin building Heo et al. [was studiedof the buildstrategies a

The resualso plays a

3.7. Measur

Measuremeasuremewithin an in[29]. The mings due to tcan be detebetween thperiod and ferences res

Esaving = Eprwhere Esavinsured (or esEpost-retro isperiod in ththe energy caused by asuch as wea

The maineed to idechanges in Performancfour M&V o

savings, including Option A: retrot isolation key parametermeasurement, Option B: retrot isolation all parameter measure-ment, Option C: whole facility, and Option D: calibrated simulation.Details of energy savings calculation methods and typical applica-

f eacV ha

savify anhortance&V cy painty

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lding towalogiece. Tted b

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ildin

4 illud in risedd sid.e. hu

retrg eles solrmale ele, theergyed aergyuildntiat

retrstrate usees. Td thed teergy

l ven of prot

diffenetentinnmenhy isg fas lesl benssment is the determination of the quantitative or qual-e of risk related to a concrete situation and a recognised

Risk assessment provides decision makers with infor-ut the risk exposure inherent in a given decision, i.e. thethat the outcome will be different from the best-guess6]. As presented earlier, a building retrot is subject tortainty factors, such as uncertainty in savings estima-

use measurements, weather forecast, the changes ofsumption patterns, system performance degradations,ncertainty factors result that investment in buildingighly uncertain. Risk assessment is therefore essentialecision makers with a sufcient level of condence toetermine the best retrot solutions.ere are many risk assessment and risk management

vailable, probability-based risk assessment methodsly the most commonly used methods. Probability-assessment methods include expected value analysis,nce criterion and coefcient of variation, risk-adjustedte technique, certainty equivalent technique, Montelation, decision analysis, real options and sensitivity].e a number of studies that have specically focused onent and uncertainty analysis of building retrots. For

enassa [75] presented a quantitative approach to deter- value of investment in sustainable building retrotsto account different uncertainties associated with lifend perceived benets of this investment. A scalable andc methodology that can support large scale investmentretrots under uncertainty was recently developed by47]. A sensitivity analysis of building energy retrots

by Gustafsson [76], which showed that life cycle costing is subject to only small changes so long as optimalre chosen.lts from the studies above show that risk assessmentn important role in a building retrot.

ement and verication of energy savings

ment and verication (M&V) is the process of usingnt to reliably determine the actual savings createddividual facility by an energy management programmeain purpose of M&V is to determine actual energy sav-he implementation of retrot measures. Energy savingsrmined by Eq. (1) through calculating the differencee energy measured (or estimated) in the pre-retrotpost-retrot period after accounting for the energy dif-ulting from non-energy retrot measure factors [28]:

e-retrfo Epost-retro Eadjust (1)

g is the energy saving; Epre-retro is the energy use mea-timated) for a dened period in the pre-retrot period;

the energy use measured (or estimated) for a denede post-retrot period; Eadjust is the difference betweenuse in the pre-retrot period and post-retrot period,ny differences in non-energy retrot measure factors,ther conditions, occupancy schedules, etc.n challenge faced in realising good M&V practice is thentify and quantify the energy changes resulting fromnon-energy retrot measure factors. In Internationale Measurement & Verication Protocol [29], there areptions that can be used to estimate and verify energy

tions oM&

energyto veriusing simportused Mefcienuncertof M&Vto validof a chis an eenergy

4. Resbuildin

Buieffortstechnoformanpresenstudies

4.1. Bu

Fig.be usecategodemanterns, i

Thebuildinsuch ageotheprovid5 yearsable enincreasable enofce bdiffere

Theof the and thnologireduceadvancLow ennaturaDetailsing ret

Fortial berepresenvirohierarcbuildinrequirementah M&V option can be found in Refs. [28,29].s been widely used to verify and measure buildingngs. For instance, Lee [44] presented three case studiesnual energy savings associated with lighting retrots- and long-term monitoring. Mozzo [77] discussed the

of M&V in performance contracting projects. Roosa [78]Option A to estimate energy savings of three energyrojects. Kromer and Schiller [79] discussed the use of

analysis in M&V and how to select an appropriate levelspecic projects. Erpelding [80] performed a M&V studythe initial energy savings calculation due to the retrotlant. The results from these studies indicated that M&Vive approach to measuring, computing and reportingngs achieved by implementing retrot measures.

h and application of retrot technologies forrformance enhancement

researchers and professionals have made signicantrds the development and application of various retrots and decision support tools to enhance building per-he-state-of-the-art of such efforts in last two decades iselow, which is intended as a summary of most of suchpleted to date.

g retrot technologies

strates major possible retrot technology types that canbuilding applications. The retrot technologies can be

into three groups, they are, supply side management,e management, and change of energy consumption pat-man factors.ot technologies for supply side management includectrical system retrots and the use of renewable energy,ar hot water, solar photovoltaics (PV), wind energy,

energy, etc., as alternative energy supply systems toctricity and/or thermal energy for buildings. In the lastre has been an increasing interest in the use of renew-

technologies as building retrot solutions due to thewareness of environmental issues. The use of renew-

technologies may bring more benets for commercialings where a utility rate structure includes time-of-useed electricity prices and demand charge is applied.ot technologies for demand side management consistegies to reduce building heating and cooling demand,

of energy efcient equipment and low energy tech-he heating and cooling demand of a building can berough retrotting building fabric and the use of otherchnologies such as air tightness, windows shading, etc.

technologies may include advance control schemes,tilation, heat recovery, thermal storage systems, etc.articular retrot technologies that can be used in build-projects can be found in Refs. [5,23,67,81,82].rent retrot measures, the cost to implement and poten-s that can be achieved are different. A diagram forg the cost to implement retrot measures versus thetal (CO2 emissions reduction) benets of the energy

illustrated in Fig. 5 [82]. It can be found that retrottingbric, building services systems and metering systemss cost investment while providing much more environ-ets, as compared to retrot measures using renewable


Fig. 4. Main categories of building retrot technologies.

energy techcern for theof retrot te

4.2. Retro

In this sbuildings ar

Guo et albased and lighting retmeet two mand the abi

Dascalakvation potetypes in fosimulationsbuilding engration of pdeveloped

g renmen

use med Fluleme

build[87] re the typ

sho buildch.low inuon bporties fnologies. Therefore, the project targets and clients con- environment have a signicant impact on the selectionchnologies.

t studies on commercial ofce buildings

ection, the major retrot studies on commercial ofcee reviewed and major outputs are summarised.. [83] developed a software tool integrating knowledge-database approaches to solving commercial buildingrot problems. Simple tests showed that this tool canain validation criteria, i.e. consistency of performance,

lity to be modied to reect other practices.i and Santamouris [84] reported on the energy conser-ntial of selected retrot options for ve ofce buildingur different European climatic zones using computer. The retrot options used include interventions on thevelope, HVAC, articial lighting systems, and the inte-assive components for heating and cooling. Rey [85]

buildinenviroously.

Theing com[86] anative ewholeet al. compaand thresultswholeapproa

Barmight based tive opstratega multiple criteria methodology for evaluating ofce to be includ

Fig. 5. Cost versus environmental benets of the enetrot strategies. This methodology takes into accounttal, socio-cultural and economic criteria simultane-

of deep retrots (i.e. whole building retrots) for exist-rcial building stock was discussed by Olgyay and Serutohrer et al. [87]. Olgyay and Seruto [86] discussed cre-nts of whole building retrot and pointed out thating retrot is a gateway to climate stabilisation. Fluhreremployed a commercial building as a case study toe difference between whole building retrot approachical retrot approach commonly used by ESCOs. The

wed that more energy (i.e. 38%) can be saved by usinging retrot, as compared to using the typical retrot

and Fiala [5] discussed how adaptive comfort theoriesence future low energy ofce refurbishment strategiesuilding surveys. The results showed that active adap-unities play an important part in future refurbishmentor existing ofce buildings. Passive interventions need

ed in future refurbishment strategies.

rgy hierarchy [82].


devel

Effectiveenergy conset al. [18]. Aauthors [19tiveness ofmethodologdevelop a dmathematicbuildings ba

Hestnesdesigned foconsidered ments, the improvemereduce builgies. Howevon the very

Coopermlope is a kebuildings. Cglazing, lowings, and el

A multi-MEthodologofce buildincluding eimpact on and cost. ORysis (PCA) a

A refurboped by Arbuildings caplan, includgets, reviewpurchase sselecting op

Decisiondetermininsented an inretrots. Thtion and di

, enesultsbuilde bu

decition cturon thed bl solmbin

decn typ3]. Fped oratiemehe card PIenergFig. 6. Architecture of the decision support system

ness of single and multiple retrot measures on theumption of ofce buildings was investigated by Chidiac

screening methodology was further developed by the] in order to determine the feasibility and cost effec-

different retrot measures for ofce buildings. Thisy uses the concept of building archetype modelling toatabase, which is then employed to formulate a set ofal equations to estimate energy consumption of ofcesed on a set of key variables.

and Kofoed [20] evaluated a set of retrot strategiesr ten existing ofce buildings. The retrot strategiesinclude combinations of building envelope improve-use of passive cooling techniques, lighting, and HVACnts. The results showed that it is possible to signicantlyding energy use through implementing retrot strate-er, the selection of retrot strategies should be based

specic building energy characteristics.an et al. [88] presented that retrotting building enve-y step to improve energy performance of commercialurrent windows retrot technologies include multiple

qualitying rele of upgradgratedrenovaarchitebased improvoptimathat co(GA). Asures iet al. [9develoincorpmanag(PIs). Tstandalist of -E coatings, noble gas lls or vacuums between glaz-ectro-chromic windows.criteria rating methodology, named as Ofce Ratingy (ORME), was developed by Roulet et al. [89] to ranking retrot scenarios according to a list of parametersnergy use for heating, cooling and other appliances,external environment, indoor environmental quality,ME was developed based on principal component anal-nd ELECTRE family algorithms.ishment guide for existing ofce buildings was devel-up [90]. In this guide, the upgrading of existing ofcen be achieved through the implementation of a six-steping determining the baseline, establishing goals & tar-ing building maintenance, housekeeping and energy

trategy, crunching time: establish or demolish, andtimal upgrade initiatives and getting started.

support tools are useful for quickly identifying andg optimal retrot measures. Flourentzou et al. [91] pre-teractive decision aid tool (TOBUS) for ofce buildingis tool has seven modules, including building descrip-mensions, building diagnostics, indoor environmental

on the comThe stud

ronmental can be impimplementried out basdue to the inot reportecase studieneeded. Thiowners to r

4.3. Retro

In literaresidential retrot expanalysis ofIt was shobuildings woped by Juan et al. [92].

rgy use, retrot scenarios, cost analysis, and report-. It can support the user in establishing a completeing state and help to identify the actions required toilding performance. Juan et al. [92] developed an inte-sion support system to recommend a set of sustainableactions for existing ofce buildings. Fig. 6 shows thee of this decision support system, which was developede consideration of trade-offs among renovation cost,uilding performance, and environmental impacts. Theution was determined using an optimisation techniquees A* graph search algorithm with genetic algorithms

ision support model for evaluating energy saving mea-ical existing ofce buildings was developed by Doukasig. 7 illustrates the model architecture. The model wasbased on the experience database through systematicon of energy data collected from the building energynt system to calculate building performance indicatorslculated PIs are then compared with the correspondings to evaluate building energy performance. A priorityy saving measures for retrots will be provided based

parison results and a nancial evaluation.ies above have demonstrated that energy and envi-performance of existing commercial ofce buildingsroved greatly if the retrot measures are selected anded properly. However, most of these studies were car-ed on numerical simulations. The actual energy savingsmplementation of the selected retrot measures wered. More research and application work with practicals on commercial ofce building retrots is essentiallys can help to increase the level of condence of buildingetrot their buildings for better performance.

t studies on residential buildings

ture, there are also a number of studies focused onbuilding retrots. Goldman et al. [94] introduced theerience in US multifamily buildings based on the

measured data from a database of dwelling units.wn that the retrot costs ($370/unit) for fuel-heatere much lower than that for electric-heat buildings


velop

($1600/unitelectric-hea

The eneroptions in sbased on anlation costsinsulation aa good retrenergy savi

The retrexamined bThe mixed as the optimapartment studies shomal solutioclimates wasubstantial the implem

Hens [99storey houusing solarbetter insuupgraded v

Bin and footprint ofhouse durinpost-use phshowed thaenvironmenin their serv

Alanne [select the mof a renovawas performodel propmising the cycle cost mof differentbenets ovepresented ascale of theand hot wapointed outsavings.

costs in 104]onominedientrimaapartd thrd rece m

ierarent wnmenergy

ttingquipadskectivd thalysitegiel ho

savio etystegs inFig. 7. Illustration of the decision support model de

). The payback periods for fuel-heat buildings andt buildings were 6 years and 2025 years, respectively.gy savings and cost effectiveness of individual retrotingle family buildings were studied by Cohen et al. [95],alysing metered energy consumption and actual instal-. The results showed that the ceiling insulation and wallre cost effective while the windows replacement is notot option since it has a very small normalised annualng (25%).ot of the heating systems in residential buildings wasy Gustafsson and Bojic [96] using the OPERA model.integer linear programming (MILP) method was usedisation technique. Optimal fenestration retrot of an

building by using MILP was studied in Ref. [97]. Bothwed that the MILP is effective in identifying the opti-ns. The retrot of residential buildings in hot and arids studied by Al-Ragom [98]. The analysis showed thatsavings could be achieved at the national level even ifentation cost was fully supported by government.] reported on the results due to the retrot of a two-

se built in 1957. It was shown that the benets of boiler and PV panels are minimal compared to usinglation, energy efcient windows, better air-tightness,entilation, and central heating.Parker [100] compared the initial and retrot ecological

a century home. The environmental performance of theg the three phases (i.e. pre-use phase, use phase andase) of its full service life was examined. The results

Theretroet al. [late ecdetermof efccycle pframe showestandanicanused.

A hbishmenviroable enretrovices e

Zavthe effings anThe anon straof panenergy

Zhaation sbuildint enhancing energy performance by renovation is antally sound action for houses with decades remainingice life.101] proposed a multi-criteria knapsack model to helpost feasible renovation actions in the conceptual phasetion project. A case analysis of a real Finnish apartmentmed to test the applicability and functionality of theosed. Gorgolewski [102] developed a method for opti-renovation strategies for housing refurbishment. A lifeethod was used to assess and compare the performance

retrot measures and to give an indication of nancialr the life of the retrot measures. Goodacre et al. [103]

cost-benet analysis framework to assess the potential benets from comprehensive upgrading of the heatingter systems in the English housing stock. The authors

that uncertainty surrounds the precise nature of energy

oped basedcombined wprocess meevaluation

Stovall eine wall rewere applieimpacts. It cially effecgreater fram

Nabingeunoccupiedair-tighteniresults shodepends oning and cooreduced byed by Doukas et al. [93].

tbenet analysis and emission reduction of lightingMalaysia residential sector were presented by Mahlia. Annualised costs and cash ow were used to calcu-ical impact of lighting retrots. The costbenet was

as a function of energy savings due to the retrot lighting systems. Dodoo et al. [105] analysed the lifery energy implication of retrotting a four-storey wood-ment building to a passive house standard. The resultsat retrotting of the building to the passive houseduced nal energy use, but the primary energy sig-ainly depends on the type of energy supply system

chical pathway towards zero carbon building refur-as proposed by Xing et al. [23] to decouple builtt from fossil fuels and integrate with local renew-. Zero carbon refurbishment can be achieved through

building fabric, the use of more efcient building ser-ment, and micro generation.as et al. [106] presented a new approach to determiningeness of house retrots based on expected energy sav-e increase in market value of the renovated buildings.s indicated that the choice of retrot scenarios dependsc urban development programmes, and the conditionuses and their environment, renovation cost, heatingng and expected increment of market value.

al. [107] developed a three-grade check and evalu-m for energy efcient retrot of existing residential

heating areas of northern China. This system was devel-

on a multi-index comprehensive evaluation methodith life cycle assessment theory, analytical hierarchy

thod, post-evaluation thought, and successful degreemethod.t al. [108] performed a series of experiments to exam-trot options. The results from the experimental testsd to an energy model to estimate whole house energywas found that external insulative sheathing is espe-tive in reducing the heat transfer through walls withing heat transfer paths.

r and Persily [109] performed a retrot study in an manufactured house to investigate the impacts ofng on ventilation rates and energy consumption. Thewed that the reduction in the house inltration rates

weather conditions and the manner in which the heat-ling system is controlled, but in general these rates were

one third due to the retrots.

Z. M

a et

al. /

Energy and

Buildings 55

(2012) 889902

899

Table 1Summary of key ndings from previous studies.

No. Reference Building type Major retrot technologies used Savings determination method Major results

1 Chidiac et al. [18] Canadian ofce building inEdmonton, Ottawa and Vancouver

Heat recovery; Day-lighting; Boiler efciency economizer;Preheat upgrade; Lighting load reduction.

Simulation program, EnergyPlus The use of ve retrot options could achieve 20% reductionin electricity consumption for Edmonton, Ottawa andVancouver, and 30%, 32% and 19% reduction in natural gasfor each of the respective cities.

2 Ascione et al. [46] A historical building hostingpresidential ofces and someclassrooms

Modication of indoor temperature set-point; Inltrationreduction; Increase of the vertical wall thermal insulation;Replacement of the old boiler with a condensation gasheater.

Numerical model calibrated byexperimental data

Could achieve 22% primary energy savings. The total costof the refurbishment would be 53,280 D with a discountedpayback period of 11 years and a net present value of30,748 D.

3 Santamouris et al.[60]

A nursery school building Green roof. Experimental test and simulation In summer period, the cooling load reductions fornon-insulated building and insulated building with thegreen roof were 1549% and 633%, compared to thatwithout using the green roof, respectively.

4 Verbeeck and Hens[69]

Five Belgian residential buildings Insulation measures; Glazing measures; Solar collectorsand PV cells.

Building simulation model and netpresent value

Roof insulation, better performing glazing and efcientheating system appeared to be the most effectivemeasures. Floor insulation appeared to be protable inmost cases (if easily accessible).

5 Dascalaki andSantamouri [84]

Five types of ofce buildings infour climatic regions in Europe

Building envelope improvement; Using passive systemsand techniques; Installation of energy saving lightingsystems and use of daylight; Improvement of heating,cooling and ventilation systems.

Simulation model developed For enclosed/light/skin dependent/cellular ofce buildings,the combination of all retrot options resulted in areduction of total energy use ranging from 48% in the NorthCoastal to 56% in the North European climatic regions.

6 Fluhrer et al. [87] Empire State building Windows upgrading; Insulated reective barriers; Tenantday-lighting, lighting and plugs; Chiller plant retrot;Using a new air handling layout unit; Demand controlventilation; Balance of direct digital controls; Tenantenergy management.

Energy and nancial modelling Can achieve a 38% reduction in energy use, save105,000 metric tonnes of CO2 over the next 15 years, andhas an incremental net present value of approximately $22million.

7 Goldman et al. [94] Multifamily buildings Heating controls and heating system equipment retrots(for fuel-heat buildings); Window retrots and insulationof water heat tank and installation of low-owshowerheads (for electric-heat buildings).

Analysis of measurement datafrom the database

Energy consumption after the retrots decreased by1215 MBtu/unit in fuel-heat buildings and by1450 kWh/unit in electric-heat buildings. Energy savingswere between 10% and 30% of pre-retrot energy use in60% of the buildings studied.

8 Cohen et al. [95] Single family buildings A range of retrot options, such as ceiling insulation, wallinsulation, foundation insulation, windows replacement,heating system retrots, etc.

Analysis of metering data andactual installation costs

Both ceiling and wall insulation are cost effective withnormalised annual consumption savings ranging between12 and 21% and average cost of conserved energy valuesbetween $1.60 and $6.50/GJ.

9 Al-Ragom [98] A two-story house Wall and roof insulation; Change of glazing system anddecrease of window area.

DOE-2.1E and simple paybackmethod

The use of wall and roof insulation and reective doubleglass with reduced window area can achieve annual energyconsumption of 293 kWh/m2 in hot and arid climates.

10 Bin and Parker[100]

A two-storey single detached brickhouse built in 1910

A high level insulation of the roof, walls, foundation andbasement oor; Air sealing and replacement of windowsand doors; The adoption of renewable energy and energyefcient appliances.

Life cycle energy analysis The environmental upfront cost of the retrots will beoffset within 2 years although the renovations resulted inadditional embodied environmental impacts.

11 Mahlia et al. [104] Residential sector Retrotting incandescent lamps with more efcientcompact uorescent lamps (CFL).

Simple energy calculation The potential monetary savings were $37 million, $74million and $111 million for 25%, 50% and 75%replacement of the lamps (for 5000 operation hours ofefcient lighting), respectively.

12 Stovall et al. [108] Typical houses in multiplelocations

Wall retrots including replacing the cladding, addinginsulation under the cladding, and air sealing methods forreplacement windows.

Energy modelling andexperimental tests

Annual utility cost savings could be 10% for most locations.Additional savings are possible through the adoption ofeither low-e storm windows or replacement vinyl-frameddouble-paned windows.

13 Nabinger andPersily [109]

An unoccupied manufacturedhouse built in 2002

Installing house wrap over the exterior walls, sealingleakage sites in the living space oor and leakages in theair distribution system, and tightening the insulated bellylayer.

Site measurement The retrots reduced building envelope leakage by 18%and duct leakage by 80%, resulted in 10% energy savings.

14 Stefano [111] The campus of MelbourneUniversity, Australia

Replace 1.2 m uorescent lighting xtures with theelectronic ballasts, T8 magnetic ballasts, T8 electronicballasts, and T5 electronic ballasts.

Simple energy calculation The installation of four lighting technology alternativeswould result in energy savings of 13.9%, 20.5%, 24.4% and64.9%, respectively.


Boait et al. [110] studied the performance of domestic groundsource heat pumps (GSHPs) in retrot installations in UK. It wasfound that the seasonal performance of GSHPs was not good asthat reported in studies from continental Europe. The thermal timeconstant of projects inc

Jaggs anas Energy Pidentify thefor apartmaspects, incand retrotcondition a

The studtechnologieimum energnote that salso be used

4.4. Researc

The studcommerciaas other typ

Xu et al.performancciency retrocategorisedcess; (b) prsustainableable develoexternal eco

Santamotal performa nursery senergy saviduring the system.

Stefano and reducebourne Unefcient ligcent lightinalternativesballasts, T8results are s

Energy eAscione et proposed aof historicato simulatecal feasibilisignicant eoptimal retof a real scatoring of a hpolymers (C

The enetation of reby Ardentebenets wetion. The resignicant e

Fonsecatation of anschools. The

different areas of a school facility, and can identify suitable light-ing solutions from 17 distinct bulb types and 38 ballast types.Gatton [114] examined particular characteristics of the predeter-mination of energy inefcient public buildings, and cost effective

retr.lausriteritage

and evaltic anedimle totrose st

progs.

clus

s papts of

ovealuarentThe m. Thn thi

ere ie in tbe uprcialroxiviountal nicast prtionsrot imathelpetsole-

ion, eroacearcilitatachinge,

ildingpropnts timisategirotsnt ofmanpre

tors ce incertarotsthe building is a critical factor to be considered in retrotorporating heat pumps.d Palmer [43] introduced an evaluation tool, namederformance Indoor Environmental Quality Retrot, to

most appropriate refurbishment or retrotting actionsent buildings. In this tool, there are four technicalluding indoor environmental quality, energy use, costs,

measures, to deal with the assessment of the buildingnd recommendations for refurbishment.ies above showed that appropriate selection of retrots is very important in building retrots to achieve max-y and environmental performance. It is worthwhile to

ome methods developed for residential buildings can in other types of buildings.

h studies on other types of buildings

ies addressing building retrots that do not fall intol ofce buildings and residential buildings are groupedes of buildings herein.

[42] developed a set of critical success factors of energye contracting (EPC) for sustainable building energy ef-t of hotel buildings. The critical success factors were

into six clusters, including (a) project organisation pro-oject nancing; (c) knowledge and innovation of EPC,

development and M&V; (d) implementation of sustain-pment strategy; (e) contractual arrangement; and (f)nomic environment.uris et al. [60] investigated energy and environmen-ance of an experimental green roof system installed inchool building. The results showed that a remarkableng was achieved due to the reduction of cooling loadsummer period after the installation of the green roof

[111] reported on the potential to save electricity electricity related carbon dioxide emissions at Mel-iversity by modelling the installation of four energyhting technology alternatives to replace 1.2 m uores-g xtures. The four energy efcient lighting technology

considered were the electronic ballasts, T8 magnetic electronic ballasts, and T5 electronic ballasts. The keyummarised in Table 1.fcient retrot of historical buildings was studied byal. [46] and Bastianini et al. [112]. Ascione et al. [46]

multi-criteria approach for the energy refurbishmentl buildings and employed a numerical energy model

the energy performance effectiveness and economi-ty of several retrot actions. The results showed thatnergy and economic benets can be achieved by using

rot actions. Bastianini et al. [112] presented the resultsle experimental work regarding the retrot and moni-istorical building using Smart carbon bre reinforcedFRP) with embedded bre optic Brillouin sensors.

rgy and environmental benets due to the implemen-trot actions in six public buildings were investigated

et al. [17]. The results showed that most signicantre from the improvement of envelope thermal insula-novation of HVAC plants and lighting systems providednergy benets as well.

et al. [113] discussed the development and implemen- easy-to-use expert system for lighting retrots in public

prototype computer-based system can evaluate eleven

energysystem

Kaktiple cof 12 sdegreefor theaesthenius Gexampbest re

Thetion tobuildin

5. Con

Thiretroity. Anand evof diffevided. Table 1work i

(1) Thablto meapp

(2) Premesig

(3) Moularetestto ben

(4) Whlatappresfac

(5) To chabu

(6) Apmeopstrretme

(7) Hucomfac

(8) Sinunretot alternatives and how they can be solved by an expert

kas et al. [115] developed a multivariate design and mul-a analysis method for building refurbishment. A totals were designed to determine the signicance, utility

priority of the retrot alternatives. This method allowsuation of economic, technical, qualitative architectural,d comfort aspects. The main public building from Vil-inas Technical University, Lithuania, was used as an

demonstrate how to use this method to determine thet options.udies also showed that retrotting is an effective solu-mote energy efciency and sustainability of existing

ions

er presented a systematic methodology for appropriateexisting buildings for energy efciency and sustainabil-rview of previous studies related to the investigationtion of energy performance and economic feasibility

retrot technologies for building applications is pro-ajor ndings from previous studies are summarised in

e concluding remarks and recommendations for futures area are as follows.

s a large body of research on building retrots avail-he public domain. However, existing buildings continuegraded at a very low rate. For instance, existing com-

building stock is currently being retrotted at a rate ofmately 2.2% per year only [86].s studies have demonstrated that energy and environ-performance of existing buildings can be improvedntly through appropriate retrots.evious studies were carried out using numerical sim-. Actual energy savings due to the implementation ofmeasures in real buildings may be different from thoseed. More research with practical case studies is needed

increase the level of condence in potential retrot.of-building retrot with comprehensive energy simu-conomic analysis and risk assessment is an effectiveh to identifying the best retrot solutions. Furtherh work and investigation in this regard are needed toe cost effective building retrots.eve building resilience due to the effects of climate

more research on low energy adaptive strategies for applications is needed.riate selection criteria and weighting factor assign-are essential in the formulation of multi-objectiveation problems to select the most cost effective retrotes. Major concerns of building owners in regard to

should be carefully considered during the develop- the optimisation problem.

factors directly affect building energy use. Morehensive research associated with investigating humanon building retrots is needed.vestment in building retrots has a high degree ofinty, more research on risk assessment of building

is also needed.


To sum up, there is still a long way for building scientists andprofessionals to go in order to make existing building stock be moreenergy efcient and environmentally sustainable.

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