Numerical investigation of buildings point thermal bridges observed on window-thermal insulation interface

Practices to avoid thermal bridges in the building shell, consists one of the key elements in the comprehensive assessment of the energy behaviour of buildings. As we are moving fast to the era of nearly zero energy buildings, both the use of non-invasive measurement techniques as well as the use of analytical and numerical models, have intensified research and substantiated best practices around this interesting issue. The sole criterion of the energy assessment of thermal bridges is the reduction of the heat losses, thus heat transfer analysis dominates the field. This short technical note presents and analyses the thermal behaviour of point thermal bridges, observed in areas of higher thermal transmittance at the joints of windows and supporting structures through different types of fasteners. Specifically, the method of direct support of windows in a layer of stone wool is considered, and the energy performance of three alternative ways of supporting the construction is examined. The heat transfer assessment of the investigated solutions is conducted with the use of numerical analysis, performed with the use of two analytical tools (THERM and HEAT3), in two- and three dimensional domains. The work concludes with substantiated suggestions in relation to the solutions that are proposed, always guided by the reduction in energy consumption. The paper aspires to provide informed answers to engineers and researchers in the field of energy efficiency of buildings, thus creating the field for future developments in the field of point thermal point bridges in window.