Long-term thermal performance of impermeably faced polyiso foam boards: Field and laboratory observations

Researchers at the National Research Council (NRC) Canada-Construction Portfolio in association with the Canadian Polyisocyanurate Council conducted collaborative research activities on the long-term thermal resistance (LTTR) of polyisocyanurate (polyiso) foam insulation with impermeable facers. Polyiso boards are commonly used in building envelope constructions (roofs and walls) in cold regions. The primary objective of the research project was to contribute towards the development of a comprehensive test procedure that could be used to measure the LTTR of polyiso foam insulation products with impermeable facers. As a part of that initiative, a project was initiated in 2001 that consisted of accelerated aging tests using thin slices in parallel with a field investigation in which polyiso boards were installed in a purpose-built test hut at the NRC's Ottawa campus. The polyiso boards installed in the field were monitored for a period of 6 years and subsequently removed from the test hut and tested in the laboratory. This paper presents the field thermal performance of the rigid polyiso foam boards with impermeable facers and critically examines its relationship with the laboratory-measured thin slice aging data. It is hoped that these observations will help construction professionals and researchers to develop a better understanding on the LTTR of impermeably faced polyiso foam insulation boards.