Methods for evaluating and improving thermal performance of wall-to-floor thermal bridges

The amount of heat loss through thermal bridges increases with the improvement of the thermal insulation performance of the building exterior wall, making thermal bridges vulnerable points of thermal insulation. The wall-to-floor thermal bridge (WFTB) takes the most considerable fraction on the building envelope and has the largest heat flux. In this study, we aimed to (1) develop a new method to evaluate the insulation performance of the WFTB, which is easier to implement in engineering, and (2) propose a strategy to reduce heat loss due to the WFTB. The apparent thermal resistance of the WFTB (R-TB), which is affected by the thermal resistance of the wall (R-W) and the insulation layer (R-I), was defined to quantify the effects of the building envelope material on the thermal performance of the WFTB. Numerical simulations and full-scale (1:1) experiments were conducted to investigate the insulation performance of the WFTB under different conditions. The results indicated that R-TB increased monotonously with an increase in R-I. However, the increase became slower with an increase in R-I, indicating that improving the insulation performance of the insulation layer cannot effectively improve RTB when R-I is relatively high. Additionally, the changing rate of RTB with respect to R-W varied among different R-I values, indicating that R-W and R-I have a synergistic effect on R-TB. An empirical formula was obtained for calculating R-TB using R-W and R-I. WFTBs in different buildings can be analyzed using this formula. Suitable insulating materials for optimizing the performance of WFTBs can thus be identified at the design stage for new buildings and the renovation of existing buildings. (C) 2020 Elsevier B.V. All rights reserved.