Thermal performance currently presents one of the major global energy challenges. The practice and profession of building surveying holds a respected position in construction, but it is not clear how successful general surveying practice is when used to assess issues and conditions associated with thermal performance. This chapter sets out to improve knowledge transfer in the understanding of building thermal performance. Thermal bridging can have a significant impact on the thermal and energy performance of the building envelope. If the building is relatively poorly insulated, thermal bridging has little influence on its overall thermal performance. Behavioural responses are primarily driven by skin temperature, and result in an individual making a conscious decision to adapt to their thermal state. The adaptive thermal comfort index was developed in response to criticism of rational indices, which have been observed to show poor predictive accuracy of thermal comfort in field studies.