Members Area
report u values

9. Conclusions

U-value optimum and cost effectiveness

Whether it is cost effective or not to start applying additional insulation, depends on the fixed costs per m2, the starting point regarding U-value and the costs of saved energy. 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, in any given location, identical for different insulation applications as long as no technical limitations occur. U-value optimum only depends on investment costs for the incremental centimetres of insulation and on the corresponding additional energy-cost-savings.

Recommendations for retrofit and for new buildings

As the U-value recommendations are robust against different initial levels of U-value and the fixed costs for insulation measures per m2, the recommended optimum U-values apply to new and existing buildings.

Cost-efficiency and post-kyoto approach

Besides the economical analysis, a climate protection approach was able to identify the contribution of the residential buildings to the achievement of a 2050 CO2 emissions reduction target of 85%, hence the U-value requirements for the total building stock. When comparing the U-values resulting from the economical and the climate protection approach, it is very interesting to note that they are comparable for any given region. This means that there are at least two fundamental argumentations, economic and environmental, to move requirements towards the U-values recommended.

U-values recommended versus current national building codes

Recommended optimum U-values resulting from the analyses based on cost-efficiency and Post-Kyoto targets are in most cases more ambitious than current national standards. The gaps differ significantly depending on countries and the building component envisaged. However, the current situation of energy prices justifies reviewing the U-value requirements in Europe.

Insulation and cooling energy demand

In residential buildings of southern Europe, thermal insulation also reduces the energy demand for cooling. Especially roof and wall, insulation provides very robust and considerable savings. A well balanced package of floor, wall and roof-insulation, combined with proper shading and a good ventilation strategy, results in a significant and cost-effective reduction in the energy demand for heating and cooling. This effect can be generalized for all residential buildings with reasonable passive cooling strategies and is quite robust in relation to “non designed behaviour” of tenants, or in case of a lower mass building.