Members Area
report u values

1. Executive Summary

The calculations of the overall energy performance of buildings, according to the EPBD has to consider an integrated approach that takes into account all building related energy losses and 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, reflecting the knowledge that it saves costs and improves comfort to ensure first a low energy demand of a building before supplying the remaining energy demand in the most efficient way.

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.

Additionally, the sharp rise in energy prices of the last years and current discussions on climate protection targets have considerably changed the boundary conditions for applying insulation to buildings in Europe. This study therefore aims to contribute to the discussion of policymakers and regulators concerning reconsideration of the national or regional required or recommended U-values for building components.

Regarding the recommendation of U-values, one could choose for a financial point of view and calculate an economic optimum for insulation levels derived from the necessary investment costs and according energy cost savings from reduced heating and cooling energy demand. Another approach is to calculate necessary insulation levels to meet climate protection targets. In this study the results for both approaches have been assessed, leading to the following conclusions:

  1. The different argumentations, both for cost effectiveness and in the climate protection approach, result in comparable maximum U-values. This means that climate protection and cost efficiency are not contradictory but can be well combined.

  2. Recommended maximum U-values resulting from the analyses based on cost-efficiency and possible Post-Kyoto targets are in most cases more ambitious than current national standards, offering room for improvement of requirements.

  3. The study demonstrates that once the cost savings for heating and cooling energy exceed the total investment costs for insulation measures, the optimum U-value (mainly determined by the contribution of insulation) is the same for new and existing buildings, as long as no technical limitations occur. In this sense the recommended U-values apply to new and existing buildings.

  4. In residential buildings of southern Europe thermal insulation also reduces the energy demand for cooling. Especially roof and wall insulation combined with proper shading and a good ventilation strategy provides very robust and considerable savings. A well balanced package of floor, wall and roof insulation results in a significant and cost-effective reduction in the energy demand for heating and cooling.