Methods for improving the thermal performance of thermal bridges of lightweight steel-framed buildings

The existence of a large number of thermal bridges in the Lightweight Steel-Framed (LSF) building leads to its energy loss. The reduction of the heat transfer of thermal bridges is crucial for increasing the thermal performance of the building envelope. In this study, the infrared technology was first used to measure the temperature of LSF buildings, and clear thermal bridge junctions were determined. The THERM software was then used to simulate the thermal bridge of the external wall-beam junction, external and internal corners of the external wall, and cornice. Finally, according to the results obtained by numerical simulation, the thermal bridge was improved for reducing its thermal loss and meeting the design standard of thermal bridge free. The results of the simulation showed that, when the thickness of the rock wool (RW) of the external wall is greater than 75 mm, the linear thermal bridge coefficient (Ψ-value) at the junction of the external wall-beam is less than 0.01 W/(m·K), which meets the design standard of thermal bridge free. When polyurethane (PU) is used instead of RW for the external wall, its external corner meets the design standard of thermal bridge free in the case where the thickness of the PU is greater than 65 mm. The internal corner of the external wall can meet the design standard of thermal bridge free when PU is used instead of RW. The thermal bridge of cornice can meet this standard by adding a PU thermal insulation layer at the indoor sides, having a thickness greater than 20 mm. Studying the thermal bridge of LSF buildings allows to promote the development of the green building technology in China.