When retrofitting a building, or constructing to higher insulating levels, the finished thickness of the building envelope must be considered. To meet the energy and space saving requirements of today’s market, builders are looking for new materials to insulate their walls that do not require new assemblies, new construction practices, or that require a large thickness to meet the desired insulating levels. Vacuum insulation panels (VIPs) have shown potential to meet or exceed today’s high insulating levels while keeping the thickness of the building envelope down. Integrating VIPs within a building envelope can significantly decrease home heating requirements, especially in heating dominated climates. However, integrating VIPs into the construction market remains a challenge, as there is an unknown service life of the panels, which degrade over time, and no data on how different climate conditions affect panel lifespan. It has been presented in literature that moisture can diffuse into panels under humid conditions, resulting in a decrease in thermal resistance over time. Recent research has used varying climate conditions in accelerated ageing testing to determine the service life of VIPs, however, a disconnect remains between results obtained under laboratory conditions and the degradation in performance observed in actual applications. This paper presents a new method to link results obtained from accelerated ageing with real time degradation, using moisture as the principle ageing mechanism. To determine how moisture affects the thermal performance of VIPs, VIPs from two manufacturers were held in a Constant Temperature and Humidity Chamber (CTHC) at 30℃ (86°F) and 90% RH for 30 days. VIPs from the first manufacturer experienced a 0.2% mass increase from an initial mass of 840 g (29.63 ounce) due to moisture and a decrease of 5% in thermal resistance. VIPs from the second manufacturer experienced a 0.05% gain in mass from an initial 246 g (8.67 ounce) and a decrease of 6.5% in thermal resistance. In finding that moisture gains within VIPs can cause a decrease in insulating capacity, the new accelerated ageing method links CTHC ageing to real time VIP degradation through moisture content of the panels.
Citation: Thermal Buildings XIV 2019