Previously, insulation thicknesses of 30 – 40 cm and wall thicknesses of up to 60 cm were required in order to attain the U-values necessary for low-energy and passive houses. On the one hand, this resulted in architecturally unattractive "loophole effects" on windows whilst also reducing the amount of available living area for fixed outer dimensions.
The above problems may be solved by utilising vacuum insulation panels (short VIP) whose thermal conductivity is 5 to 10 times lower as compared to conventional insulation materials such as foam or fibre. However, it should be noted that these fragile vacuum insulation panels are not well suited to being machined on-site. Prefabrication by the facade element manufacturer can significantly reduce the risk of errors.
The goal of the project was to develop ultra-slim vacuum-insulated precast concrete units suitable for passive houses with an average U-value (incl. all thermal bridges) of only 0.15 W/m²K. These VIPs can also be replaced at a later date. A demonstration building was constructed in Ravensburg (Germany) to field-test the VIP-insulated precast concrete units.