In situ measurement of the heat loss coefficient of thermal bridges in a building envelope

Abstract One way to achieve carbon neutrality is by improving the energy performance of existing buildings, which requires accurate measurements. In particular, accurate measurement of heat loss coefficient (HLC) is critical because a building envelope is an important parameter of the energy performance analysis. The international standard for measuring HLC is heat flow meter (HFM) method in ISO 9869-1, which can be used to obtain the HLC at representative points on the building envelope. However, this approach does not account for the HLC of thermal bridges, which means that adding up the HLCs obtained for individual elements of the building envelope underestimates the total HLC of the building. In this study, the in situ thermal bridge measurement (TBM) method, which combines the HFM method and the coheating test, was proposed. In situ TBM can quantitatively measure the HLCs of multiple thermal bridges within an existing building envelope without requiring information on the internal structure or material properties. Measurement tests in an experimental chamber demonstrated that the in situ TBM method can be used to quantify the HLC of thermal bridges, which are missed when the HFM method is used alone.