Study of the edge thermal bridging effect in vacuum insulation panels: Steady and unsteady-state approaches using numerical and experimental methods

This study presents an experimental and numerical investigation on edge thermal bridges effects in vacuum insulation panels. For this purpose, an experimental campaign was carried out using a guarded hot plate apparatus to determine the linear thermal transmittance between different types of panel joints assemblies. Numerical modelling under steady and unsteady boundary conditions were carried out and compared with the experimental results. Focusing on a VIP suitable for external thermal insulation composite systems (ETICS), a sensitivity analysis regarding different edge protection materials, thickness and panels dimensions were also carried out and discussed. Additionally, the contribution of the point thermal transmittance of mechanical fixing devices was numerically evaluated. Finally, transient thermal simulations are applied to VIP based ETICS in different support walls. The results allowed for the quantification of the influence of the edge thermal bridging effects on equivalent thermal conductivity, as well as on the overall thermal performance of ETICS walls. The size of the panels, edge material and air gaps between panels are key-factors to be considered for minimizing linear thermal bridges in VIP solutions. VIP based ETICS walls showed high thermal delay when compared with a conventional ETICS wall.