Thermal bridging analysis on cladding systems for building facades

Abstract

Cladding systems have become an attractive solution in energy renovation of existing buildings since they combine multiple benefits. In such systems, the use of a metallic frame and brackets, which penetrates the thermal insulation layer, creates point thermal bridges that are usually neglected by thermal insulation regulations due to their calculation complexity and their supposed small magnitude in overall heat losses. The objective of this study is to perform a parametric analysis to quantify the magnitude of this thermal bridging effect. All necessary calculations are performed using a detailed 3-dimensional numerical analysis approach in order to overcome oversimplifications found in most thermal bridge estimation methods. Results of the analysis are applied in a refurbishment study of an existing office building in order to underline the significance of the problem under investigation, in practice. As it is shown, point thermal bridge effects in cladding systems can constitute a significant part of buildings’ thermal balance. Neglecting their presence can lead to significant underestimation of actual heat flows which can account for 5% to almost 20% of total heat flows through the building envelope, depending mostly on the thermal transmittance of the load bearing wall and the ventilation characteristics of the air cavity.