Entwicklung von hybriden Wärmedämmsteinen aus LAC

Development of new heat-insulating masonry blocks made of LAC.

The actual discussion of the necessity of sustainable reduction of primary energy for heating of housing structures and of the reduction of CO₂-emissions led the University of Luxembourg to issue a project aimed to develop hybrid lightweight concrete blocks with high heat-insulating properties. The progressing Energy Saving Regulation (EnEV) in Germany and the grand-ducal Regulation in Luxembourg [1] are limiting the annual primary energy consumption for housing structures and office buildings. Supplementary, these regulations are also limiting the heat transfer coefficient U for the transmission of the heat flow through the outer walls. In Luxembourg e.g. the actual U-value is limited to maximal 0,32 W/m²K. Based on the measured values, the static and thermal properties of the materials themselves (e.g. lightweight concrete with open structure) as well as the whole masonry bricks and blocks, taken from the European free market, were tested and simulated by the finite element method to study their weak spot and to use this experience for the construction of new prototypes. It was revealed that it is suggestive to separate the load bearing from a thermal construction part in the masonry block. The market study showed, that is only possible to reach certainly the declared limit values of the thermal and mechanical properties of the masonry block by separating the load-bearing from the thermal function of the block.