Grenzen der Dämmung opaker Bauteile

The limits of insulation for opaque structural elements.

The German Federal government's Energy Concept pledges an 80 % reduction in the use of fossil fuels in buildings by 2050. Since around 80 % of existing buildings will still be standing in 2050, this target primarily encompasses the current building stock. The main tools available for use in achieving this target are improvements to the thermal envelope and the use of renewable energies. Yet there are limits to the scope for using these tools. This begs the question of the extent to which each tool can help achieve the target. The level of thermal protection depends directly on the heat transfer coefficients (U-values) that can be achieved in each structural element. Current U-values are in the order of 0.30 to 0.14 W/(m²K). In the present article, we investigate any significant reduction in heat transfer coefficients that can be achieved in future using insulation measures. The properties of as yet undeveloped insulation materials are of course unknown, and hence for the purposes of our investigation cannot be considered in full. It will however be possible to demonstrate basic principles which will also apply to any future insulation materials, and to derive from these specific lower limits for U-values.