Retrofitting Timber Frame Walls with Vacuum Insulation Panels

A U-value of 0.35 W/(m2K) (about 10 cm mineral wool) in walls was required in Norwegian buildings in the 1970s (Building regulations 1969), whereas today the requirement is an U-value of 0.18 W/(m2K) (TEK 1997), i.e., nearly 50 % less. The passive houses have even higher requirements. Retrofitting of buildings with vacuum insulation panels (VIPs) might be advantageous as passive house standards may be achieved without major changes to the building structure. Adding insulation on the exterior may prevent moisture problems as the temperature in the old wall structure rises, and furthermore reduces the effect of thermal bridges. However, a vapor- tight layer on the cold side increases the risk of condensation inside the wall, especially if the thermal resistance of the VIPs is reduced due to aging or puncture.

This work investigates ways of retrofitting timber frame walls, both with VIPs on the cold side and with VIPs on the warm side. A wall section with different test fields were placed between two climate chambers with indoor climate and outdoor climate. Moisture and temperature conditions in the wall were measured, analyzed, and compared with numerical simulations and calculations.