Analysis of the temperature dependence of the thermal conductivity in Vacuum Insulation Panels

Over the last few years, the adoption of Vacuum Insulation Panels (VIPs) in building envelopes has increased. However, in order to obtain a correct implementation of VIPs in buildings, it is crucial to conduct a proper analysis of the thermal bridging, the service life and the ageing effects at both the design stage and during building operation. A further factor that should be considered is the dependency of thermal conductivity on temperature. In this paper, an experimental campaign has been carried out to evaluate the variation in the thermal conductivity of VIPs with the average temperature and to qualitatively assess the heat transfer contributions that affect this variation. The study has also been devoted to evaluating the effect of a variation in the thermal conductivity considering various VIP ageing stages. Moreover, dynamic heat transfer simulations have been performed, using a validated model, to investigate the impact of considering a temperature dependent thermal conductivity on the overall thermal behaviour of a building roof with VIP-based insulation.