Vacuum Insulation Panels in Wood Frame Wall Constructions

Energy use in buildings accounts for a significant part of the energy use and greenhouse gas emissions. New building regulations and new measures have been introduced to improve the energy efficiency of buildings. In these buildings the envelope constructions will have significant amounts of traditional thermal insulation, e.g. wall thicknesses up to about 400 mm are expected in passive houses. Such large thicknesses are not desirable due to several reasons, e.g. floor area considerations, efficient material use and need for new construction techniques.

Vacuum insulation panels (VIPs) are regarded as one of the most promising existing high performance thermal insulation solutions on the market today. Thermal performances 5 to 10 times better than traditional insulation materials (e.g. mineral wool) are achieved, resulting in substantial slimmer constructions. However, the robustness of building envelope systems applying VIPs has been questioned. In addition, thermal bridging due to the vacuum insulation panel envelope and load bearing elements of the walls may have a large effect on the overall thermal performance. Degradation of thermal performance of VIPs with time is also a crucial issue due to moisture and air diffusion through the panel envelope.

In this work the thermal performance and robustness of vacuum insulation panels in wood frame wall constructions were studied by hot box measurements and numerical simulations. The thermal performance of three different wall configurations was examined. VIPs were sandwiched between traditional insulation in walls where the load bearing elements were standard 36 mm thick wooden studs, I-profiled studs and U-profiled studs. The measured mean values of the thermal transmittance (U-value) were 0.09 W/(m2K) with 36 mm wooden studs, 0.10 W/(m2K) with U-profiled studs and 0.11 W/(m2K) with I-profiled studs.