VIP service life assessment: Interactions between barrier laminates and core material, and significance of silica core ageing

As a result of temperature and humidity vacuum insulation panels (VIP) age: their thermal resistance decreases due to the combined effect of internal pressure and solid conduction increase. For given conditions this depends on the duration of the exposure and on the permeance of the envelope, as well as on the hygric and thermal behaviour of the core material. This paper begins by assessing the severity of the various building applications with regard to the VIP. It then presents the main behaviours and models needed and explains the life evaluation approach under stationary conditions. Furthermore particular attention is paid to the ageing of silica core material. It concludes that for a realistic estimation of the service life one needs to take into account both the thermal and hygric behaviour of the core material, the permeance of air and water vapour through the envelope, the temperature and humidity service conditions, and the thickness of the panel.