Thermal bridging problems on advanced cladding systems and smart building facades

Double-skin facades (DSFs) are a technology that lies behind innovative energy efficient facade systems. While it provides a potential for high energy efficient buildings, other important parameters, like point thermal bridge problems, are in most cases overlooked. The aim of this study is to investigate the magnitude of this approach and the effect it might has on the overall heat flow estimation in buildings. The study performs a numerical analysis of heat flow through the points where such effects are found, in order to analyse their nature under different design parameters selection like the use of thermal breaks, the substrate wall material, the thermal insulation thickness and the type of anchors used to securely connect both facade skins. The results are then applied to a case-study office building aiming at quantifying the overall contribution of point thermal bridges to heat flows through the building envelope. As the analysis shows, point thermal bridges in well-insulated envelopes have a heat-loss similar to the one from 1 m(2) of facade's wall. The overall effect at DSFs can surpass 25% of total envelope heat flow, leading to a large underestimation of actual heat flows through the building envelope. Overlooking their contribution, as many European national energy efficiency regulations currently do for the shake of simplicity, has a significant effect in widening the gap between predicted and actual energy efficiency of buildings. (C) 2018 Elsevier Ltd. All rights reserved.