Experimental verification of the theoretical aging of vacuum insulated panels

Vacuum insulation panels (VIPs) encompass a higher thermal resistance per unit of thickness compared to any other kind of insulation. However, their aging has often shown some critical concerns. To support the broader use of VIPs in the building sector, their physical properties, and in particular their thermal conductivity, over long-periods should remain consistent. This study investigates the effect of extreme temperature and relative humidity cycling on the service life and thermal conductivity of VIPs. The scope is to validate existing theoretical aging models for VIPs. First, the experimental results of the thermal conductivity for five VIPs in pristine and in laboratory-accelerated conditions are reported. The thermal conductivity in pristine conditions of the selected materials ranged between 0.0028 and 0.007 W/m K. The results of the thermal conductivity values after several aging conditions are reported in the temperature range from −20 °C to +40 °C. Then, an analytical aging method is employed to validate the collected data. Results show that aging has a more significant impact on the performance of VIPs with a core of fiberglass-core than on VIPs with a core of fumed silica. However, for all the investigated VIPs the service life corresponding to the thermal conductivity of 0.008 W/m K was higher than 25 years, confirming the reliability of these insulating systems.