1. Introduction

The Energy Performance of BuildingsDirective, (EPBD, Directive 2010/31/EU) andparticularly Article 4.1 recital 14, obligesMember States (MSs) to “assure thatminimum energy performance requirementsfor buildings or building units are set with aview to achieving cost‐optimal levels”. MSsshall also “take the necessary measures toensure that minimum energy performancerequirements are set for building elementsthat form part of the building envelope andthat have a significant impact on theenergy performance of the buildingenvelope when they are replaced orretrofitted, with a view to achieving cost‐optimal levels”.

The cost‐optimal level is defined in Article2.14 of the EPBD as “the energyperformance level which leads to the lowestcost during the estimated economiclifecycle” from two different perspectives:financial (looking at the investment itselfat the building level) and macro economic(looking at the costs and benefits of energyefficiency for society as a whole).

The cost‐optimal levels must be calculatedfollowing specific guidelines. Article 3 andAnnex I of the EPBD define the energyperformance calculation methodology.Article 5 and Annex III set out how toundertake comparative analysis between thedifferent options that results in thedefinition of the cost‐optimal levels. Energyperformance must be calculated accordingto a specific methodology, which must alsobe developed by MSs in line with therequirements set out in Annex I of the EPBD.

MSs must report on the comparisonbetween the minimum energy performancerequirements and calculated cost‐optimallevels using the comparative methodologyframework provided in Articles 5.2, 5.3and 5.4 and Annex III of the EPBD.

To support MSs in calculating the cost‐optimal levels, the EU publishedregulations for the comparativemethodology framework (CommissionDelegated Regulation, 244/2012) andaccompanying guidelines (2012/C 115/01)[1].

This report deals with questions relating toArticles 3‐8 of the EPBD, as well as Annexes Iand III, i.e., it is not limited to issues relatedto cost‐optimality, but also touches ongeneral issues related to procedures forcalculating a building’s energy performance.It describes the main discussions andconclusions reached by the Concerted Action(CA) EPBD on these issues.

2. Objectives

In March 2012, the Commission publishedthe comparative methodology frameworkfor calculating cost‐optimal levels ofminimum energy performancerequirements for buildings and buildingelements. The comparative methodologyframework was established in accordancewith Annex III of the EPBD and itdifferentiates between new and existingbuildings and between different categoriesof buildings. Furthermore, a documentguiding MSs on how to performthe cost‐optimum calculations andanalyses was published in April 2012.

OVERVIEW AND OUTCOMES

AUGUST 201 5

AUTHORSSKirsten EngelundThomsen,Kim B. Wittchen,Danish BuildingResearch Institute(SBi), AalborgUniversity

Energy performance requirements using

[1] Both documents are available at the European Commission’s web site:http://ec.europa.eu/energy/efficiency/buildings/buildings_en.htm

Cost-optimal levels

MSs have calculated their cost‐optimallevels of minimum energy performancerequirements using the comparativemethodology framework and relevantparameters, such as climatic conditionsand the practical accessibility of energyinfrastructure, and compared the resultsof this calculation to the minimum energyperformance requirements in force. If thiscalculation demonstrated a deviationfrom the requirements larger than 15%,the MS should have taken action to modifythe requirements, or indicated a way tomake the requirements come within a 15%deviation within a reasonable period oftime.

One of the primary objectives of the CAEPBD’s work during 2010‐2015 has been tofacilitate exchange of experiencesbetween MSs and the EC on how to carryout calculation of MSs’ cost‐optimalenergy performance levels. Additionally,MSs were offered the opportunity todiscuss the reports required by the EC andto suggest improvements to theaccompanying guidelines. Due to MScalculation of the cost‐optimal levels, itwas possible to create an overview of thepotential impact on MS minimum energyperformance requirements.

The CEN has developed a number ofstandards. Though these standards arenot directly implemented in everynational energy performance procedure,most countries use CEN‐compatibleapproaches. The package of CENstandards relating to the EPBD areundergoing revision during 2013‐2016, andnew versions of the Standards areexpected by 2016. MSs are following theprogress of this work, and there is closecollaboration between the CA EPBD andthe CEN. In particular, the CA EPBD hasprovided the CEN with input towardspreparation of the revised set ofstandards. A Liaison Committee wasestablished with the objective of makingMSs’ needs regarding the usability of theStandards explicit, in order to contributeto the effectiveness of the standards fromthe MSs’ perspective. The LiaisonCommittee acts as a liaison between theCEN and the EPB Committee (formerlyEnergy Demand Management Committee‐EDMC, representing the MSs) during thedevelopment of the revised EPBD‐CENstandards, and interacts with theEuropean Commission and the CA EPBD tomutually benefit from the knowledge andexperience available. Collaborationbetween MSs and the CEN is ongoing.

The introduction of Nearly Zero‐EnergyBuildings (NZEB) will require an increasedfocus on calculation procedures and onwhich renewable energy sources (RES) areto be included in future NZEBrequirements at a national level.Methodologies for calculating NZEB energyperformance and inclusion of RES in thecalculations have been investigated andare also discussed in the report “Towards2020: Nearly zero‐energy buildings”available from www.epbd‐ca.eu. TheCommission Delegated Regulation (No.244/2012) states that the calculation ofcosts for establishing NZEBs should beincluded as a variant in the MS calculationexercise to identify the cost‐optimallevels for new and possibly also forexisting buildings.

With the increased energy performancerequirements of NZEBs included in futurenational building regulations, compliancechecking of new buildings’ performancebecomes increasingly important. Thesignificance of quality control in theentire building process (from design,through construction to the final buildingstages) is a topic that has been discussed,but will require further attention.

3. Analysis of insights

Since the publication of the EPBD Directive2010/31/EU, MSs have performed theirown national calculations of cost‐optimalenergy performance levels for new andexisting buildings. Therefore, the focus ofdiscussions within the CA EPBD has been onexchange of experiences regarding thecalculations, the identification ofreference buildings and energy savingmeasures, the interpretation of the rulesand guidelines provided by the EC, and theimplications on national energyperformance requirements.

The following topics are presented in thissection:

> energy performance calculationprocedures;

> calculating cost‐optimal energyperformance levels;

> energy performance requirements fornew and existing buildings.

Some of these topics were also discussedwithin a wider context in the CA EPBD andtherefore are also addressed fromdifferent perspectives in other reportsavailable from www.epbd‐ca.eu.

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3.1. Energy performancecalculation procedures

Energy performance methodologies havemostly been dealt with before theDirective 2010/31/EU, therefore onlyspecial topics that have been discussedafter 2010 are described in this section.For information about topics previouslydiscussed, information is availableonline[2].

3.1.1 Handling exceptions andinnovative systemsInnovative and not‐commonly‐knownsystems and materials, e.g., in preparationfor constructing NZEBs, cannot always behandled directly by the national energyperformance calculation tools. A surveyamong MSs showed that there are threefundamentally different ways of handlingexceptions and innovative systems in theMS energy performance calculations:

1. The performance of the innovativecomponent or system may be evaluatedwith a separate (unofficial, butvalidated) tool. The results from thisunofficial evaluation would then createinput for the official tool(s) to give thesame effect as calculated by theseparate tool used for evaluating theperformance of the innovativecomponent/system. An example of thisapproach is the calculation ofpreheating of ventilation air inunderground ducts using a separatesoftware. The calculated input is thendealt with as increased heat recoveryefficiency in the official calculationtool, resulting in the same annualimprovement of energy performance ascalculated by the separate tool. Thismethod can be more or less formalisedthrough its general acceptance and theimplementation of verificationrequirements. Among the advantagesare: the method is quick and flexible;comparison between different tools ispossible; the user can use specialisttools when appropriate. On thedisadvantages side are: problems withresult verification; results may dependon selected input data based onunreliable (user‐dependant) methods;lack of compatibility of results; unclearlegal aspect; CEN standards are notavailable for all innovativetechnologies.

2. No single calculation tool is prescribed,and it is thus possible to find a widevariety (ranging from ordinary, quasi‐stationary monthly methods toadvanced dynamic simulations) amongthose accredited tools that are capableof calculating or simulatingadvanced/innovative technology ormaterial. The advantages of thismethod are: it is flexible as anyappropriate tool may be used; it willboost competition in the market.Among the disadvantages are: differenttools will give different results therebygiving the possibility to use the toolthat gives the most favourable results;it is necessary to create additionalquality control for results from varioustools. The disadvantages are consideredso serious that this alternative is notrecommended.

3. Advanced or innovative technologiescan be used only after calculationroutines have been implemented in theofficial calculation tool(s). Themanufacturers need to provide thenecessary information for evaluatingand implementing the requestedmethodology. The main advantages ofthis method are: it provides a widemarket introduction for newtechnologies; it is legally acceptable;the quality of the information isuniform and coherent. The maindisadvantages are: implementation isslow and expensive; it is costly for theauthorities; it increases the complexityof the tool; it may exclude small,innovative market players. With thisapproach, it is suggested that groups ofmanufacturers in a MS jointly pay fortesting and development as well asvalidation, which will produce anacceptable procedure (which may,however, require independentdevelopment).

The best solution would be a combinationof the different approaches. The methodchosen and the way different methods arecombined depend to a high degree on thelegal framework of each MS. Using acombined approach allows for the optimalsolution in any context and offersincreased flexibility. An example of acombined methodology would be: when aMS, which is normally using method one orthree, in case the calculations need toaccount for an innovative system, allowsthe use of alternative calculation tools.

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[2] See www.epbd­ca.eu/outcomes/CA_Annex_4_Procedures.pdfand www.epbd­ca.eu/outcomes/CT_Reports_14­04­2011/CT4_Procedures.pdf

The use of the alternative tool should,however, only be allowed afterapplication and proper validation of thetool and models used.

It will be increasingly important to enableinclusion of innovative systems andmaterials in energy performancecalculations as requirements approachNZEB levels.

3.1.2 Introduction of renewableenergy sources in the energyperformance calculationsMSs have different approaches on how tohandle RES in their energy performancecalculations and legislation. Electricityproduction from photovoltaics (PV) isgenerally accepted in most MSs, but thereare differences in how the electricity isaccounted for in the national calculationprocedures. A few MSs allow for an annualbalancing of the electricity production,while the rest of the MSs balance theelectricity production on a monthly basis –primarily due to the overall balancingperiod of the national calculation tools,which in most cases is monthly (Figure 1).More or less the same differences andapproaches apply for RES‐based heatingand cooling production.

Beyond considering different RES sourceswhen calculating buildings’ energyperformance, another issue is the primaryenergy‐weighting factor used in thecalculation of the RES contribution andthe amount of RES energy that can besubtracted from the calculated energyperformance. The primary energy factorsfor different types of RES vary among MSs(Figure 2). The primary energy factor forbiomass varies between 0 and 1.08. Thisdiversity reflects different political waysof looking at biomass, beyond purecombustion chemistry. A primary energyfactor of 0 reflects 100% clean fuel, while1.08 may indicate that biomass is a scarceresource and not always possible toreplace. In the first case, almost noenergy saving measures will be profitablein case of a major renovation. The samevariation in calculations is found for otherheat sources, e.g., district heating thatvaries between 0 and 1.52.

From a sample of twenty MSs thatprovided detailed information on thisissue, seventeen MSs allow inclusion ofelectricity from PV, while twelve allowelectricity from local wind‐turbines andcombined heat and power (CHP) to beincluded in the calculated energyperformance of buildings. Nine of thesetwenty MSs also allow the inclusion ofelectricity from hydropower.

Production of heat from RES is, like theproduction of electricity, also accountedfor differently in different MSs. Here thediversity in possible sources of heatproduction is much more significant thanfor the production of electricity, andmethods of handling these differentsources vary significantly.

For instance, passive cooling is taken intoaccount in most MSs’ national calculationtools, while active cooling technologiesbased on RES are in most cases notaddressed, or handled indirectly in thenational tool for calculating buildings’energy performance.

Figure 1: Balancing period for electricity productionfrom RES for selected MSs.

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Figure 2:Primary energy

factors for electricity,biomass, and districtheating (average for

selected MSs).

One way for MSs to increase the share ofRES in a building is to offer subsidies tobuilding owners for setting up systemsfor RES production. From inquiries sentto selected MSs, it seems that the mostsubsidised RES systems for electricitygeneration are PV and on‐site windturbines. The most subsidised RESsystems for heating are solar thermal‐and heat pump‐based systems. For RES‐based solar cooling, only one MS has asubsidy scheme and other RES‐basedcooling production methods are onlysubsidised in a few MSs. In some MSs, thepossibility of obtaining subsidy for RES‐based systems depends on thecircumstances: either a local utilitycompany offers subsidies for their localcustomers, or subsidies only apply ifcertain conditions are fulfilled, e.g.,replacement of an old oil burner with aground coupled heat pump.

Since the implementation of NZEBs mustbecome the norm by 2018‐2020, there isan ever‐increasing need for MSs to clarifytheir understanding of NZEBs. It is notpossible to compare NZEB requirementsfor MSs that already have an establisheddefinition, due to variations in climateand in the way requirements are set up,but there are significant variations in theunderstanding of NZEB among MSs. Thistopic needs close monitoring in thefuture, and further information can befound in the report “Towards 2020: NearlyZero‐Energy Buildings” available fromwww.epbd‐ca.eu.

It is important for MSs to ensure thatunrealistic low primary energy factors donot hinder deployment of NZEB effortsand effective energy saving measures inexisting buildings.

3.1.3 Estimating realistic energysavings in Energy PerformanceCertificatesGiven the fact that most MSs use fixed orother kinds of default values as boundaryconditions for input data for energyperformance calculations (Figure 3), it isnot surprising that calculated energyperformance normally differs frommeasured energy consumption.Consequently, the calculated energysavings due to energy upgrades suggestedin the Energy Performance Certificate(EPC) will also deviate from the energysavings actually achieved. On the otherhand, the aim of the EPC is not tocalculate real energy consumption andhence energy savings but, rather, tocompare building energy performanceunder a standard pattern of use.

Adjusting input boundary conditions toactual values may result in realistic (incomparison with measured energyconsumption) calculations of energydemands. This is also the case for thesimpler, quasi‐stationary calculation toolsusing monthly average values.

The optimal solution for creating EPCs andcalculating realistic energy savings isachieved by carrying out threecalculations: one calculation using defaultvalues to calculate the label itself andthen one with actual input parameters forcalculating energy performance bothbefore and after implementing energysaving measures. This suggestion however,is not required in any MS. Additionally,actual values may be difficult to identify,so it is necessary to make adjustments forreality. Even if actual values are available,there are still issues that cause calculatedenergy savings to differ from the savings

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Figure 3: Type of input parameters used in MSs for internal loads in energy performance calculations.

achieved: the ‘prebound’ effect, i.e.,before refurbishment, users of buildingswith poor energy efficiency are using lessenergy than predicted, and the ‘rebound’effect, where users of energy‐refurbishedbuildings use more energy[3] thanpredicted; therefore the amount of energysaved is lower than expected.

There is no doubt that this issue willcontinue to be a central part of MSs’discussions on achieved energy savingsand on how the EPC can be used as a toolto promote and assess energy savings. TheEPC as a tool for building benchmarking,independent of user behaviour, isundoubtedly very valuable. This iscomparable to car energy labelling,where although no‐one expects to be ableto obtain the same degree of economy asstated by the manufacturer, it isgenerally agreed that the relativecomparison between two cars is reliable.EPCs should continue to act as abenchmarking tool for buildings that isindependent of user behaviour. It mayhowever be supplemented by additionalcalculations for realistic energyconsumption and hence savings valid forthe actual building and its use, e.g., useof realistic indoor temperature,ventilation rate, hot water consumption,pattern of use of heating systems inmoderate southern EU climates, etc.

3.1.4 Buildings as providers ofdemand side flexibilityA collaboration between the threeConcerted Actions (i.e., the CA on theRenewable Energy Sources Directive, theCA on the Energy Efficienty Directive andthe CA on the Energy Performance ofBuildings Directive) has been establishedto investigate the possible promotionwithin the three Directives of DemandSide Flexibility (DSF), i.e., flexible use ofelectricity by customers based on pricesignals.

DSF has the potential to contribute to anaffordable, reliable and sustainableelectricity system. DSF is considered tohave many and significant potentialbenefits as it increases the flexibility of theelectricity system. The existing electricitysystem already includes a high degree offlexibility provided mostly by stand‐bypower plants and a few large customers.

The increase of intermittent (renewable)generation will result in a greater need

for flexibility. However, DSF is notexpected to deliver this flexibility alone:storage, fuel shift technologies, moreinterconnection between MSs and optimalfunctioning of the EU internal energymarket will all contribute to meeting theneed for flexibility.

Buildings conditioned by a heat pump or bydirect electric heating, especially NZEBswith large inertia and, thus, with a longtime constant, will be able to offer inducedor postponed use of electricity especially inperiods with fluctuating electricityproduction from renewable energy. In thisway, the building can use extra electricity inperiods with abundance and help reducingthe peak‐demand by postponing demand inperiods with shortage. A building’s thermalmass and its built‐in potential water storagecan provide flexibility by shifting thetemperature setpoint within the acceptablecomfort range (or even more in hoursoutside use) and thus allow for accelerationor delay of energy demand. In case ofoverheating or undercooling a building inperiods of abundant RES‐based electricity,the building’s overall energy consumptionwill increase, while overall CO2 emissionsmay well decrease. If DSF is going to beincluded in MS building energy requirementsin the future, there is thus a clear need fornew regulation and calculation procedures,both taking into account the value offlexibility for the electricity grid.

There is little doubt that DSF in generalwill draw increased interest in balancingthe growing production of electricity fromRES and hence the fluctuating productionthat is sometimes out of phase withtraditional electricity demand. This willcall upon buildings to become activeplayers and provide their share of DSF inthe future by induced use of greenelectricity at periods with abundance anddeferred use in periods with shortage ofgreen electricity.

It is not always possible to directlyaddress innovative and uncommonsystems and materials in the nationalmost energy performance calculationtools, e.g., in preparation forconstructing NZEBs. Threefundamentally different ways ofhandling exceptions and innovativesystems were identified.

There is a large diversity among MSsregarding inclusion of RES in nationaldefinitions and requirements. In some

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[3] Minna Sunikka­Blanka & Ray Galvina (2012). Introducing the prebound effect: the gap between performance and actualenergy consumption. Building Research & Information. Volume 40, Issue 3, 2012.

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cases, RES contributions are calculatedwith a primary energy factor of 0,making almost no energy savingmeasures cost effective.

Standard calculations, as carried out inthe EPC, are the best tool forbenchmarking buildings withoutinfluence of the users. Estimates ofrealistic energy savings requireadditional calculations, taking intoaccount user behaviour.

3.2 Calculating cost­optimalenergy performance levels

The EPBD requires MSs to report on thecomparison between their legal minimumenergy performance requirements andcalculated cost‐optimal levels using thecomparative methodology framework.The Comparative Methodology Frameworkis accompanied by Guidelines from theCommission to enable the MSs to:

> Establish at least nine referencebuildings – one for new buildings andtwo for existing buildings subject tomajor renovation, for single‐family,multi‐family, and office buildingsrespectively. In addition to officebuildings, MSs must establish referencebuildings for other non‐residentialbuilding types for which energyperformance requirements exist, e.g.,educational buildings, hospitals, hotelsand restaurants, sports facilities,wholesale and retail trade servicesbuildings, and other types of energy‐consuming buildings. Several buildingtypes can be represented by the samereference building type, e.g., hotelsand prisons, or offices and universities,if appropriate.

> Define packages of energy efficiencymeasures to be applied to thesereference buildings.

> Assess the primary and final energyneeds of the reference buildings andthe impact of the applied improvementmeasures.

> Calculate the life cycle cost of thebuilding after energy efficiencymeasures are implemented, by applyingthe principles outlined in thecomparative methodology framework.

The Guidelines give reasonablerecommendations on how to carry outcalculations of the cost‐optimal levels andprovide an overview of the inputparameters and results. However, some

MSs have decided not to use the tablessuggested in the Guidelines, but ratheradapt the data to the format used in theirown national calculation tool in order tomake reporting more targeted to theirneeds.

The use of only one reference building perbuilding type does not cover the widedifferences in the real building stock.According to experience from test runs,3‐4 reference buildings for each buildingtype would be necessary in order to get arepresentative picture of the building stockdiversity. When analysing the existingbuilding stock, it is possible to identify alarge number of different building typesdue to differences in construction and use.Based on this, some MSs have defined up to184 (in the case of The Netherlands)different reference buildings to describetheir building stock, while other MSs simplyused the minimum number (nine) asdescribed in the Guidelines.

For any reference building, a number ofvariations on packages of energy savingmeasures must be calculated in order toidentify the cost‐optimal level. There is alarge diversity in the number ofcalculations carried out in different MSs.The Flemish region of Belgium, forexample, used random variations ofenergy saving measures and calculatedmore than 100,000 combinations for eachreference building. Other MSs havecarefully selected, among logicalpackages, the variation of energy savingmeasures to calculate, and have thuslimited the number of calculationssignificantly.

The methodology for calculating cost‐optimal levels seems to work well, as itdelivers interesting results and the effortneeded to make the calculations ismanageable. Calculation of numerousvariants of energy‐saving measures orpackages of measures is necessary in orderto obtain accurate cost‐optimum values. Aminimum of ten variants per referencebuilding must be calculated in order toidentify the cost‐optimal level, butsomewhere between twenty and fourtyvariants seems to be the ideal number inorder to more clearly identify the cost‐optimal level. Even so, many of thecalculated cost curves are quite flat (i.e.,they show little difference in energyperformance compared to investmentlevels) and, in many instances, noindividual, clear optimal point could beidentified. This means that many MSs find

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a cost‐optimal range of measures bycombining the building envelope and thetechnical systems rather than anindividual optimal point. The cost‐optimallevel is often defined at the lower end ofthe range to ensure the lowest possibleenergy consumption within the optimalrange of costs (Figure 4).

Most MSs (27) have submitted[4] theircalculation of their cost‐optimal levels.Lessons learned from the cost‐optimalcalculations vary significantly among MSs.Exchange of experiences and informationduring CA EPBD discussions (see box on theright) have been of great value for thedevelopment of the current Guidelines, andpotential further advice provided by theCommission.

Implications of cost‐optimalitycalculations on national energyperformance requirements

Examples from selected MS calculations ofthe cost‐optimal levels for new andexisting buildings are given next in orderto illustrate the huge variety among MSsin setting requirements that are withinthe acceptable range of 15% from thecalculated cost‐optimal level.

In Slovakia, the 2013 minimum energyperformance requirement for blocks of flatswas 126 kWh/m².year. Due to the results ofthe calculation of the cost‐optimal levels,these requirements will be tightened to63 kWh/m².year in 2016. The NZEBrequirement, which will be the minimumrequirement by 2019 (for public buildings)and by 2021 (for all buildings) is estimatedto be 32 kWh/m².year (see Figure 5).

[4] http://ec.europa.eu/energy/en/topics/energy­efficiency/buildings

Lessons learned relating mainly to thecalculation process

> The input from experts with experiencein this kind of calculation (e.g.,development of scenarios for referencebuildings) is essential to supportlegislative changes, and in particular toaddress real complexities rather thanjust presenting academic exercises forsimple example buildings. This wouldresult in more widely applicableGuidelines and better results.

> Minimum energy performancerequirements are usually set at thenational level and do not take intoaccount the possibilities for RES at theregional, local, district or site level.Therefore, the cost‐optimal level isoften a compromise, using only thosetechnologies that can be used in alllocalities. As a result, some real cost‐optimal packages with RES may bemissed. More flexible minimumrequirements with a focus on localconditions should be recommended totrigger the use of RES depending on thespecific local conditions, e.g., a localsource for small‐scale hydropower.

> Cost‐optimal levels derived from non‐renewable primary energy might notalways be cost‐optimal for individualusers because they are based onanalyses of reference buildings ratherthan a specific building, as required bythe EPBD. Decisions on energy savingmeasures for the building owner mightneed technical‐economic analyses thatare adjusted to the actual building.

Wish list for additional advice

> Provide further guidance on choosing thetype and characteristics of referencebuildings.

> Provide further clarification of economicscenarios.

> Improve description of how to establishtypologies for new residential buildings.

> Define standard forms for reporting onenergy management systems.

> Define common variants of packages forenergy efficiency.

> Extend the calculation period to 60 yearsto reflect the typical economic life ofbuildings. In particular, the 30‐yearperiod does not fully account for thebenefit of installing longer‐lasting fabricimprovements.

Figure 4:Example graph

showing the cost­optimal range of

different packagesof energy saving

measures.

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In the Flemish region of Belgium, thecost‐optimal level for residential and non‐residential buildings was calculated in thespring of 2013. In Flanders, the primaryenergy use (kWh/m².year) is not anindicator used for checking compliancewith Flemish building regulations.Instead, the so‐called E‐level (primaryenergy consumption divided by areference value) is used. The results(Table 1) indicate that the cost‐optimallevel for residential buildings with PV isE50, which should be compared with the2014 requirement of E60. For offices andschools, the cost‐optimal level without PVis E57, which is close to what is alreadydefined in the 2014 Flemish buildingregulations. Since the E57 level is close tothe 2014 requirement, further steps areplanned in order to gradually reach NZEBlevels by 2021 (and E55 by 2016).

In the expected 2021 Flemish buildingregulations, the E‐level requirements willbe E30 for residential buildings, and E40for offices and schools. These moredemanding levels represent the expectedfuture cost‐effective levels.

In order to find the cost‐optimal point,different packages of energy‐savingmeasures were chosen, reflecting theinteraction between various measures.Generation of random combinations ofmeasures is believed to help identify amore accurate optimum. These randomlygenerated combinations also includedimprobable and clearly non‐optimalpackages. Although those were excludedfrom the calculations, the number ofpackages calculated per referencebuilding was still more than 100,000.

Table 2 summarises the Danish cost‐optimal levels in comparison with theenergy requirements for new buildings inthe 2010 Danish building regulations(BR10). Analyses are based on a financialperspective (i.e., effects on the wholebuilding stock). The gap between theBR10 energy regulations and thecost‐optimal levels is shown as apercentage of the cost‐optimal level ofrequirements in kWh/m².year primaryenergy, inclusive of renewables.A negative gap indicates that therequirements in the Danish BR10 aretighter than the cost‐optimal level.The BR10 includes the 2010‐2015minimum energy performancerequirements in Denmark. Two voluntaryclasses, LEB2015 (Low Energy class 2015)

Figure 5: Calculation of costs and primary energy use in block of flatswith indication of the current requirements level, the requirementlevel from 2016 and the 2020 level (NZEB) for different heatingsources (example from Slovakia). Conversion factors for primaryenergy used in the calculations are biomass: 0.2; natural gas: 1.36;CHP district heating: 0.7. The blue curve (a) represents heat pumpsand biomass solutions while the red curve (b) represents heatsources that are feasible for all locations.

Table 1:Comparison ofenergyperformance levelsfor new andexisting buildings inFlanders, Belgium.

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and B2020 (Building class 2020) are bothalready defined in the BR10 as prospectsfor minimum requirements for 2015 and2020 respectively. Only the relevant heatsupply sources in relation to Danish heatplans are included in the calculations.

In relation to the new housing examples,the present minimum energy requirementsin the BR10 all show gaps that arenegative, with a deviation from the cost‐optimal point of up to 16%. With theplanned tightening of the requirements fornew houses in 2015 and again in 2020, theenergy requirements can be expected tobe tighter than the cost‐optimal point inthe current price structure. However, itmust be expected that the costs for thenecessary improvements and for newtechnologies will decrease, and hencefuture requirements and cost‐optimalpoints will eventually converge.

In relation to new office buildings, thereis a gap of 31% between cost‐optimalityand the 2010 requirement. In relation tothe 2015 and 2020 requirements, thereare negative gaps to the point of cost‐optimality based on 2014 prices.

If the gaps for all new buildings areweighted on an average, based on a mixof building types and heat supply for newbuildings, in Denmark, there is a gap of3% on average for new buildings, in thecurrent regulations (BR10). The plannedtightening of the energy performancerequirements in 2015 and 2020, usingtoday's prices, is 34% and 49% more strictthan the cost‐optimal levels.

Many MSs have noted that one or morebuilding types had more lax minimumenergy performance requirements thanthe calculated cost‐optimal levels(resulting in more than 15% differencebetween the two). In many cases, theidentified gap has already been addressedby changing the national legislations, orwill soon result in new, tighter national

minimum energy performancerequirements. A survey showed that ninecountries saw a tightening of 11% to 25%on the energy performance requirementbetween 2011 and 2014.

In most cases, the curve defining thecalculated cost‐optimal level is almosthorizontal over a range of equally cost‐optimal combinations of energy savingmeasures around the cost‐optimal level.This means that there is little additionalinvestment required to obtain additionalenergy savings if the building is within thecost‐optimal range. Many MSs have thusdecided to define their cost‐optimal levelat the lower end of the range to ensurethe lowest possible energy consumptionwithin the optimal cost range.

Most MSs have experienced that one ormore building types have more lax energyperformance requirements than thecalculated cost‐optimal levels (with morethan 15% difference between the two).

3.3 Energy performancerequirements for new andexisting buildings

MSs deal with setting energy performancerequirements for new and existingbuildings in different ways.

Especially for existing buildings subject tomajor renovations, the diversity isimmense. Some MSs set requirements onlyfor those individual building componentsthat are being renovated or replaced,while other MSs set requirements for thewhole building.

Setting requirements for new buildingsalso differs among MSs, not only in termsof energy performance levels, but also interms of other properties in the buildingenvelope. For example, there aresubstantial differences in the units ofmeasure used by MSs (kWh/m2,

Table 2: Cost optimal requirements for new buildings in the Danish BuildingRegulations 2010. For the different building types and heat supply, the table shows the

cost optimum in kWh/m2.year primary energy and the percentual gap between thecost­optimal level and the 2010­2015 requirements

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comparison with reference building,kg CO2/m2). There are also differencesamong the properties of the buildingenvelope. For example, infiltration ishandled very differently by MSs (e.g.,compulsory tests versus qualitycertification programmes). On the otherhand, most MSs tend to set limits on U‐values. There are also very different waysof checking compliance. For example,Sweden set requirements that are verifiedthrough comparison with the measuredenergy consumption two years aftertaking the building into use. Designersthus need to establish a margin that canabsorb the variations caused by userbehaviour and different climates.

Compliance checking and settingrequirements for new and existingbuildings has been one of the focus areasduring 2010‐2015. Additionally, settingrequirements for technical buildingsystems has also been discussed.

3.3.1 Energy performancerequirements for renovation ofexisting buildings

The two main methods for settingrequirements for existing buildingssubject to major renovation both haveadvantages and disadvantages (Table 3).

The main advantages of componentrequirements are that they are easy toexplain, confirm and enforce, andtherefore they offer the possibility forincreased user acceptance. On the otherhand, this method is difficult to regulate(especially indoor works are difficult orimpossible to check) and does not lead toimprovements of adjacent areas orcomponents. Moreover, it is not easy todecide which measure to implement firstwithout a holistic approach.

Applying whole‐building requirementsmakes it easy to set ambitious energy

Table 3:Pros and cons forthe differentapproaches forsetting energyperformancerequirements toexisting buildingssubject to (major)renovation.

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Figure 6:Number of MSs that

set requirementsfor existing

buildings subject tomajor renovationas whole­building

or componentrequirements.

requirements for major renovations,change of use and extensions, and toavoid costly energy measures, which mayonly have a small effect on the energydemand of the building. However, thereare no requirements ensuring the use ofenergy‐efficient components for normalmaintenance or minor refurbishments,and there is a risk that additional costsdue to requirements for the wholebuilding may be a hinderance forimplementing energy‐saving measures atall. Moreover, in many cases, especially inthe case of refurbishment of smallbuildings, the owner and craftsmen arethe only players involved and there is noarchitect nor engineer to encourage (ordesign and calculate) a holistic approach.

A combination of whole‐building andcomponent requirements makes it easierto tighten the requirements, as there arepossible alternative solutions that canmeet the overall requirement. However,this approach also implies the negativepoints for each of the individual paths.

Only two MSs/regions have only whole‐building requirements in force, while sevenMSs/regions rely solely on componentrequirements. The other MSs/regionsrequire a combination of component andwhole‐building requirements (Figure 6).

Some MSs, even some of those MSs withcombined requirements, have suggestedthat setting requirements for buildingcomponents that are being replaced orrenovated is sufficient to ensure anoptimal energy performance of therenovated building. In an earlier study[5], ithas even been suggested that “compliancewith whole‐building energy performancerequirements may hinder majorrenovations if the procedure for meetingthe regulations is too complicated or toocostly”. It seems that a combination ofwhole building and componentrequirements is the optimal solution toensure a holistic approach for energysavings in the building stock in general.

3.3.2 Requirements fortechnical building systems innew and existing buildings

The EPBD uses the term technical buildingsystem (TBS) in the recitals and Articles 1,2, 8 and 11. Article 8 calls for minimumstandards for energy performance,installation, dimensioning, adjustmentand control. These standards areobligatory in existing buildings, and theyrefer to system performance rather thanproduct performance or whole buildingperformance.

Most MSs have TBS performanceregulations of some kind in place andabout two‐thirds report having the samerequirements for TBS for new andexisting buildings. The EPBD does notrequire that MSs set regulations for TBSin new buildings, though most MSs applyTBS regulations to new, as well asexisting buildings. In most cases, thereare no requirements for carrying out awhole building energy performancecalculation to prove compliance, asminimum TBS requirements areconsidered sufficient.

When TBSs are being installed in newbuildings, regulations might require designcalculations to be carried out so thatsystem energy performance can beevaluated. However, in existing buildings,the original design information for TBSswill not usually be available, nor willbuilding data (in the form of dimensions,heat loss, etc.). So, in the context ofsystem replacement in existing buildings,it may be too difficult and time‐consuming to carry out a rigorous systemdesign and performance evaluation. TBSrequirements are thus often limited toperformance requirements for eachindividual component.

More detailed information about TBSregulations is found in the report on“Inspections”, available fromwww.epbd‐ca.eu.

[5] Thomsen et al (2009). Thresholds related to renovation of buildings ­ EPBD definitions and rules. SBi 2009:02. DanishBuilding Research Institute, Aalborg University.

3.3.3 Checking and enforcingcompliance for new buildings

MSs have different approaches todemonstrating compliance with energyperformance requirements, and some haveadapted their regulations to implementArticle 27 of the EPBD on penalties.

With the progressive increase of theenergy performance requirementsincluded in national regulations, the issueof checking compliance of energyperformance of new buildings becomesincreasingly important. An effectivecompliance scheme becomes a crucialelement of regulation, especially in thecontext of NZEB.

As previously indicated, the requirementsset by MSs affect different parameters ofthe building (e.g., U‐values, infiltration,system efficiency, overall performance,etc.). MSs may choose to check differentelements at different stages.

Compliance with energy performancerequirements is checked at different stagesof the building process in different MSs.Some MSs even check compliance severaltimes during the building process (Figure 7).

In addition to the energy performancerequirements for new buildings, mostcountries also set other requirements.Figure 8 shows some of these requirements.

Compliance check and quality controlregarding the airtightness, thermalbridges, summer comfort and availabilityof daylight in new buildings requireincreased attention, as buildings aremoving towards NZEB, since these topicsaccount for an increasing share ofbuildings’ total energy consumption.

A special compliance check philosophy isin place in Sweden, based on anoperational rating system applied to newhouses or apartments after two years ofoperation. It is not necessary to measuresingle parameters as long as the measuredvalue of energy consumption complieswith the building code.

A combination of whole building andcomponent requirements seems to bethe optimal solution for ensuringimplementation of the most effectiveenergy saving measures in existingbuildings – not only when undertakingmajor renovations, but also whenrenovating minor parts of the building.

Many MSs have chosen to prescribe thesame TBS component requirements fornew, as well as for existing buildingswhen replacing TBSs.

With the progressive increase of energyperformance requirements included innational regulations, the issue ofchecking new buildings’ compliance withrequirements becomes more and moreimportant. An effective compliancescheme becomes a crucial element ofregulation, especially in the context ofNZEB.

Figure 7:Most countries check compliance with the requirements for newbuildings on more than one occasion.

Figure 8: MSs that set requirements in addition to energyperformance requirements for new buildings.

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4. Main outcomes

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5. Lessons learned andrecommendations

Energy performance calculationprocedures

Innovative and not‐commonly‐knownsystems and materials cannot always behandled directly by the national energyperformance calculation tools. It isrecommended that MSs ensure smoothinclusion of innovative systems in energyperformance calculation methodologies inorder to promote the design of NZEBs.Development of new energy efficientproducts is often ahead of the capabilitiesof energy performance calculaton tools,and there is a need for flexibility toinclude them in the calculations.

MSs implement different approaches as tohow to handle renewable energy sources(RES) in their energy performancecalculations and legislation. In some casescontributions from RES, e.g., biomass, arecalculated using a primary energy factorof 0, making almost no energy savingmeasures cost‐effective. It is importantfor MSs to ensure that primary energyfactors do not hinder implementation ofNZEBs. According to the EPBD, it isrequired that the RES be located “nearby”the building if it is to be taken intoaccount in the building’s energyperformance. Also, there are significantdifferences among MSs on how far“nearby” is, ranging from “at the buildingand the building site” to “within theborders of the MS”.

Most MSs use standard inputs for energyperformance calculations and thus theseresults are generally not in line with themeasured energy consumption. Calculatedenergy savings presented in the EPC aretherefore often different from the energysavings actually experienced. However,standard calculations, as carried out forthe EPC, are the best tool forbenchmarking buildings without influenceof the users, while a supplementarycalculation can provide realistic energysavings. Cost‐effective renovation towardsNZEB requires improved methods forestimating realistic energy savings.Several MSs have issued differentguidelines for calculating realistic energyuse and savings, as summarised in a reportfrom CIBSE[6].

Calculating cost‐optimal energyperformance levels

There is an increased focus on setting outadequate and cost‐optimal energyrequirements in the national buildingregulations. Additionally, the cost‐optimalcalculation exercise resulted inrecommendations for an update of theGuidelines to the Regulations forcost‐optimal calculations, e.g., moreguidance on choosing the type andcharacteristics of reference buildings,more clarification on economic scenariosand improved Guidelines of how toestablish building typologies.

In most cases, the curve defining thecalculated cost‐optimal level is almosthorizontal over a range of equally cost‐optimal combinations of energy savingmeasures around the cost‐optimal level.It is recommended that MSs set theirrequirements at the lower end of thecost‐optimal range.

Many MSs have experienced that one ormore building types have looser energyperformance requirements than thecalculated cost‐optimal levels. Many MSs areworking on closing, or have already closed,this gap by implementing tighter nationalminimum energy performance requirementsfor new and existing buildings.

Energy performance requirements fornew and existing buildings

With the increased energy performancerequirements for NZEB included in futurenational building regulations, compliancechecking of the performance of newbuildings becomes increasingly important.Compliance with requirements is not limitedto energy performance requirements, but inseveral MSs also includes other aspects likeairtightness, daylight levels, summercomfort, etc. There are differentmethodologies for compliance checks usedin MSs depending on the assessment methodand the requirement(s) to be checked.

There are two fundamentally differentapproaches to setting requirements forexisting buildings subject to majorrenovation, namely whole buildingrequirements or component requirements.Neither of the two methods is ideal and itis recommended that a combination of thetwo is implemented. The main advantages

[6] Cheshire D. & Menezes A.C. (2013). Evaluating operational energy performance of buildings at the design stage.CIBSE TM54:2013.

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The sole responsibility for the content of this report lies with the authors. It does notnecessarily reflect the opinion of the European Union. Neither the EASME nor theEuropean Commission are responsible for any use that may be made of the informationcontained therein.

The content of this report is included in the book “2016 – Implementing the EnergyPerformance of Buildings Directive (EPBD) Featuring Country Reports”,ISBN 978‐972‐8646‐32‐5, © ADENE 2015

More details on the IEE Programme can be found atec.europa.eu/energy/intelligent

This individual report and the full 2016 book are available atwww.epbd‐ca.eu and www.buildup.eu

of a combined approach are: it is easy tostrengthen requirements when analternative is available; the approach ishelpful during the setup of fundingschemes; it is possible to achieve the costoptimum for each component; and thereis an easy and direct connection to theenergy performance indicator(s). It isrecommended that requirements shouldensure maximum energy savings withoutimplementing requirements that are toorigid, too costly or too complicated.Works that do not require a buildingpermit or which are performed inside thebuilding are especially difficult tomonitor.

Setting standards for technicalbuilding systems (TBS) is obligatory inexisting buildings, and it refers tosystem performance rather thanproduct performance or wholebuilding performance. Even though itis not obligatory to set standards forTBS in new buildings, it isrecommended to prescribe the samecomponent requirements in new andexisting buildings. This will make iteasier for the industry to deliverhighly efficient components as onlyone set of rules apply, andconsequently prices will decrease asthe market increases.

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