Members Area
report u values

2. Introduction

The European Directive on Energy Performance of Buildings (EPBD), which came into force 16 December 2002 to be implemented in the legislation of Member States in 2006, aims to improve the overall energy efficiency of new buildings and large existing buildings during significant renovation. Because the building sector being responsible for about 40% of Europe’s total energy consumption, the EPBD is an important step for the European Union to reach in order that it should achieve the level of saving required by the Kyoto Agreement; the EU is committed to reduce CO2 emissions by 8 per cent by 2010 relative to the base year of 1990.

The impact of the EPBD has been quantified in earlier Eurima studies(1) for the potential monetary savings, investments and CO2 savings. All studies were carried out by Ecofys. The basis for the analysis is the ECOFYS energy model of the European building stock BEAM (Built Environment Analysis Model).

Questions concerning the EPBD and its implementation were covered in the following Ecofys-reports:

Report Content
Mitigation of CO2 Emissions from the Building Stock – Beyond the EU Directive on the Energy Performance of Buildings

Report II, February 2004

Reduction of CO2 emissions in the EU15 building stock resulting from current and extended EPBD. Excursus:

Effects of insulation on cooling demand.

Cost-Effective Climate Protection in the EU Building Stock

Report III, February 2005

Economic assessment of CO2 mitigation measures and retrofit packages in the EU15 countries
Cost-Effective Climate Protection in the Building Stock of the New EU Member States - Beyond the EU Directive on the Energy Performance of Buildings

Reports IV and V, August 2005

Reduction of CO2-emissions in the new Eastern European member states (New EU8) resulting from current and extended EPBD including an economic assessment of retrofit measures and packages.
Sensitivity Analysis of cost effective Climate Protection in the EU Building stock

Report VI, June 2006

Sensitivity analysis of the calculations on cost- efficiency for the EU15 and NEW8 (reports III to V) on basis of 5 energy-price scenarios.

The reports cover the topics of CO2-emission savings and cost efficiency from energy saving measures in the existing EU15 and the New EU8 countries. The proven cost effectiveness of the investigated retrofit packages confirms the validity of the principles of the Trias Energetica, which postulate that energy- saving measures should be implemented to reduce demand first. The remaining energy demand then should be preferably generated by renewable technologies, or with energy efficient technologies based on fossil fuels.

The reports conclude that these principles can be implemented by the EPBD, following its transposition in national regulations, by the introduction of minimum insulation levels (or maximum U-values) in addition to the requirements for overall energy performance.

The calculations of the overall energy performance of buildings, according to the EPBD has to consider an integrated approach, that takes into account the calculation rules given in a suite of CEN standards for all building related energy losses and energy gains. National or regional energy performance requirements are given in national or regional regulations for fully integrated overall energy performance. In many countries additional requirements on the maximum energy transmission for single building components expressed in U-values or R-values are given. However the national U-value requirements for building components (roof, floor, wall, windows, etc.) often describe minimum requirements that do not reflect the economic optimum or specific environmental targets.

The study aims to contribute to the discussion concerning reconsideration of the national or regional required or recommended U-values for building components. Regarding the recommendation of U-values, there are two lines of argument that are reasonable to follow:

  1. Cost effectiveness : In article 6 ‘Existing buildings’ the EPBD states that when buildings with a total useful floor area over 1 000 m2 undergo major renovation, their energy performance should be upgraded in order to meet minimum requirements in so far as this is technically, functionally and economically feasible. It is essential to assess which measures are technically, functionally and economically feasible for average local market conditions.

  2. Climate change : In the Post-Kyoto discussion the EU25 ministers for the environment set the target for the reduction of greenhouse gas emissions as 70-90% by 2050. Taking retrofit cycles of 30-50 years in the building stock into account, each building which undergoes refurbishment in 2010 has to fulfil these targets. To implement the targets on a wide scale in 2010 their feasibility has to be demonstrated now. This raises the question, what does the target of 70-90% reduction actually mean for the maximum energy consumption and the associated minimum insulation standard of retrofitted houses in different European climates?

In order to make recommendations for minimum thermal performance levels for building component in Europe, the following steps have been taken:

  • Background work description:

    • Development of a European heating and cooling degree days maps for the EU25

    • Calculation of insulation impact on cooling energy demand in southern Europe

  • Recommendation for U-values (thermal performance levels) based on cost-effectiveness and 2 different price scenarios from the Ecofys-report “Sensitivity analysis of cost effective climate protection in the EU building stock”, which refers to:

    • WEO reference scenario and

    • Peak price scenario

  • Minimum requirements calculations on overall energy performance to meet the Post-Kyoto targets and conclusion on according insulation standards.

The detailed approach, giving results and their interpretation is described in the following chapters.

1 Eurima Ecofys studies: see: