Heat Loss Due To Thermal Bridges In Buildings: Fid-Bau Portal

Heat Loss Due To Thermal Bridges In Buildings

Fang, J B. / tarot, R A. / Childs, K W. / Courville, G. E.

Building envelopes often contain numerous highly conductive heat flow paths, called thermal bridges, which are major sources of heat loss and deterioration of building materials due to moisture condensation. Some examples of thermal bridges occurring in office buildings are presented. Infrared thermography was used to identify the locations and magnitudes of thermally defective areas resulting from inadequate construction, design, or substandard workmanship in existing buildings. Due to the large thermal inertia of building components and transient conditions caused by fluctuating outdoor and indoor temperatures, long measurement periods are required. This makes thermography impractical for quantifying the heat loss. In order to estimate the heat loss rate from thermal bridges and to obtain a better understanding of the physical processes involved, a two-dimensional heat flow model has been developed for transient heat conduction within the exterior wall/intermediate floor systems. The calculated results from the mathematical model are compared with available experimental data. An in-situ measurement technique, which is currently under development at NBS for quantifying the energy loss due to thermal bridges, is described.