An Analytical Model for Calculating Thermal Bridge Effects in High Performance Building Enclosure

Abstract

Although vacuum insulation panels (VIPs) are excellent thermal insulators, edge effects decrease their overall thermal performance. Moreover, they are often used with protections, such as integration into a panel. These panels typically use spacers that cause a significant additional thermal bridge. The effect of this thermal bridge is either determined accurately with numerical simulation tools or estimated with simple thermal resistance networks. The first approach is laborious, while the latter approach lacks accuracy. This study therefore presents and validates an analytical approximation model for calculating this thermal edge effect. A comparison of this model with numerical simulation shows that it can be applied with an inaccuracy of <10%. The total inaccuracy, however, also includes an error due to the schematization of the edge of the building panel. Yet, this model appears to be very useful for estimation of the linear thermal transmittance of the edge of building panels.

Vacuum insulation panels for building applications: A review and beyond

“…The resistance of the edge spacer is included in the equation to determine the fictive temperatures of the face sheets in front of the thermal bridge and the analytical formulae for those values are given by Tenpierik et al [30]. It seems that the linear thermal transmittance depends on the environmental temperatures, but it can be proven that, after some rewriting, that these are eliminated from the equation.…”

“…Two modifications are made [30] on the previous model to meet to the scale of a building component: First, the heat balance at the corners of the component is modified. Second, the equation for the linear transmittance is extended to include the additional heat flow through the edges.…”

“…Originally, the high barrier laminate consisted of stainless steel or glass [41] envelopes, aluminium foils or laminated polymer films but gradually developed into laminated metallized polymer films with a low GTR and WVTR to decrease the thermal conductivity of the foil. The analytical models [29,30] consider the thermal bridges due to the VIP envelope and they are developed to understand the systems of heat transfer at the panel edges, which is impossible if only numerical simulations are used. The models of [29,71] start with the same formulae of the direct heat transmission coefficient as in Eq.…”

“…Analytical models [28][29][30] and numerical investigations [28,[31][32][33][34] have been proposed on the calculation and prediction of this thermal bridge effect. Numerical investigations or parts catalogues are more likely to be used to be used to estimate thermal bridge effects in the common application of VIPs [35][36][37][38][39][40], while analytical models are of more interest to be programmed in an ordinary spreadsheets.…”

Vacuum Insulation Panels (VIPs) for building construction industry – A review of the contemporary developments and future directions

“…Nussbaumer et al [60] also observed the reduced thermal bridging effect when expanded polystyrene was used as a facing in building components. Tenpierik et al [61] and Quenard and Sallee [53] calculated thermal bridging effect of facing and spacers and found that aluminium and stainless steel facing caused larger values of linear thermal transmittance as compared to polyester facing. Same trend was observed for spacers made up of aluminium as compared to thermoplastic spacer.…”