Methodology

See paper on EPLabel (521 kb PDF) presented at IEECB'06 in Frankfurt for more detail of EPLabel’s graduated response methodology for the energy certification of non-residential buildings on the basis of their actual annual energy use.

For ease of description, we have broken down the process required to produce an energy certificate based on an operational rating into five main steps. What have we got? STEP1 - Collect relevant data and calculate the appropriate building energy performance indicator(s). *What does it mean?* STEP 2 - Identify appropriate benchmarks with which the indicators can be compared. STEP 3 - Compare the indicators with the benchmarks to grade the building's energy efficiency. What can we do? STEP 4 - Identify cost-effective energy saving measures. Tell everyone about it: STEP 5 - Bring together all the relevant data on the energy performance certificate. The EPLabel methodology employs benchmarks expressed in delivered energy terms for both electricity and fossil/thermal energy as these continue to be the primary information on which effective benchmarking systems rely. The approach requires two benchmark values, Rr (regulatory standard) and Rs (stock median), for both the electricity and fossil fuel/thermal energy use, to be designated for each building sub-type in each country. Due to their lack of national benchmarks, some countries elected to use sub-types and the corresponding benchmarks from other countries. To deal with the issue of setting values for Rr, many Partners decided to set Rr at a fixed percentage of the Rs value eg 50% or 70%. This followed the lead of the UK where it was felt that the existing Good Practice benchmarks were less robust than the Typical values and a fixed percentage across all sub-sectors could end a lot of futile argument. Alignment with the EPBD Although the EPBD came into force on 4 January 2006, Member States can request an additional period of up to three years for introducing the mandatory energy certification requirements of Article 7. Implementation of Article 7.3 in many countries may start with an Operational Rating approach requiring eligible buildings to provide a summary of their energy use, weight the different fuels used (e.g. by primary energy or by kg CO₂), report their energy performance indicator (EPI) and compare it with simple benchmarks (where these are available). Energy Performance Indicator The measured Energy Performance Indicator (EPI) is defined by draft CEN Standard (CEN prEN 15203, 2005) as the weighted sum of the actual annual consumption of all energywares (also called the Operational Energy Rating) divided by the building’s total conditioned floor area. Building energy use For buildings with active renewable energy systems, the same CEN Standard also recommends reporting the Building Energy Use (BEU): the net weighted delivered energy that would be used if the renewable energy systems were not present. The differences between the EPI and BEU are illustrated by the diagram below. A briefing note provides more details and gives worked examples for five different energy supply situations.
Development of Benchmarks at 3 levels We have categorised building energy benchmarks at three levels of sophistication: Level 1: simple, usually derived from stock statistics for the type of building concerned. Level 2: corrected, taking account of special energy uses not included in the Level 1 benchmarks. Level 3: customised, taking more detailed account of the building's schedule of accommodation, activities and use.
Climate adjustment and weather corrections Most benchmarks are national values and, by inference, are related to an average national climate. Historically, in many countries, it has been customary simply to adjust the actual energy to take account of the difference between the local and this average national climate. This has the benefit of enabling all buildings in the country to be compared on a single basis. However, it suffers from two serious flaws: 1. In most buildings the energy used solely for space heating purposes is not separately metered. Where, for example, gas is used for heating, it is often also used for producing hot water and often also for cooking. In some cases, it will be used for co-generation (CHP) and/or absorption cooling. In all-electric buildings, identifying the electricity used for space heating may be even more problematic. Given that most countries have substantial regional climatic variations, the potential error that might be introduced by correcting an estimated value for heating energy use is unacceptably large. 2. By adjusting actual energy to a national average climate, one is effectively moving the building from its real location to an 'average' location for that country. If one uses this adjusted building energy performance to assess the viability of energy saving measures, the results could be grossly misleading. The alternative of offering the adjusted performance to judge the building's energy efficiency but using the unadjusted performance to judge energy saving measures would be too confusing. We have also found it dangerous to adjust actual consumption, as touch is lost with reality; and adjusted consumption can be confused with actual consumption. In order to overcome these shortcomings, EPLabel adopted a two stage process (see diagram): 1. Climate correction of benchmarks: In order to cope with regional climatic variations, EPLabel adjusts the 'national' benchmarks for fuel/thermal and electrical energy use in order to create benchmarks applicable to the regional average climate for the building. This is done by defining national and regional climate indices (eg degree days to a given base) for heating and cooling. The part of the benchmarks for fuel/thermal and electrical energy use which are heating and cooling climate dependent are defined separately for each sub-sector. This part is adjusted pro rata the ratio of the national and the building's regional climate indices. 2. Weather correction of actual energy: This takes account of the differences in weather experienced by the building during the year of the assessment compared with the regional average climate. It will also deals with local year-on-year weather variations experienced by the building, which is important when data for more than one year is being reported. Due to the inevitable approximations involved, EPLabel recommends that an adjustment of the actual energy for the regional average climate should only be made when year-on-year comparisons are being undertaken. To do the weather correction, the user enters the heating and cooling (if applicable) climate indices for the year of assessment for the building's region. The actual energy is climate corrected pro rata these climate indices and the 20 year average climate index for the region. We do not recommend making a weather correction for cooling unless the annual cooling energy has been sub-metered (to check it is consistent with the assumed part of the benchmarks for fuel/thermal and electrical energy use which is cooling climate dependent in that sub-sector). Diagram illustrating methodology for climate and weather corrections
Energy weighting factors Weighting factors need to be applied to measured energy values in order to convert them into a common currency. Benchmarks are also commonly available as energy values, often with electricity and fuel/thermal given separately, and must also have weighting factors applied to them. EPLabel has developed an approach to energy weighting factors consistent with the draft CEN standards on implementation of the EPBD. The following choice of energy weighting factors is offered: Carbon Dioxide emissions (kgCO₂/kWh) Primary Energy use Energy cost Policy-weighting The choice of energy weighting factor type is normally determined by national specifications for building energy certificates. The above choices are all allowed by the (draft) CEN Standards. Additionally, there is flexibility to select the context for these factors from the following: National factors Local factors EU factors Further details are given in a briefing note.
	For a detailed review of how energy performance certification might work for buildings in operation, using actual energy consumption, see a benchmarking operational energy discussion paper (215 kb PDF)
EPLabel's other focus was on developing the Level 3 benchmarking approach. These allow more meaningful and fairer assessments of the energy use and CO₂ emissions of individual buildings than can be done by comparison with bulk energy statistics for the sector. The procedure needed to be as compatible as practicable with the Level 1 and 2 assessments that may well be employed in initial statutory implementations of Article 7.3. In due course, it might become verified and accredited as an alternative to the Level 2 correction.
	For technical detail describing the principles of customised benchmarks see the Europrosper final summary report (281kb PDF)

A graduated response and unification of the 3 benchmarking levels Governments are sensitive to accusations of creating unnecessary red tape and “gold plating” European Directives. However, in practice a minimum implementation of the EPBD could be more disruptive than a well-integrated one: some annoying hurdles to jump, instead of an integrated driver of continuous improvement. The solution offered by EPLabel is a graduated response which allows a progressive introduction of EPBD Article 7.3 to suit the knowledge available in each country/region for each building sector and the level of resources an organisation is able to apply. An easy entry level exists for cases where detailed information is hard to get or may be less rewarding, whilst progressively more detailed assessment is available, providing more insight, where the need and scope for improvement is greater, all within a cohesive framework which makes assessments at different levels as mutually consistent as possible.
	See paper on EPLabel (521 kb PDF) presented at IEECB'06 in Frankfurt for more detail of EPLabel’s graduated response methodology for the energy certification of non-residential buildings on the basis of their actual annual energy use.