The reduced thermal resistance due to thermal bridging through steel and concrete framing can have a significant impact on the whole building energy performance. Uncertainty about the thermal performance of the building envelope can lead to inefficient design of HVACsystems, building operation inefficiencies, inadequate condensation resistance at intersections of components and compromised occupant comfort. ASHRAE 1365-RP's objective was to provide thermal performance data of 40 common building envelope details for mid- and high-rise construction. The goal of the project was to develop procedures and a catalogue that will allow designers quick and straightforward access to information but with sufficient complexity and accuracy to reduce uncertainty in the thermal performance of building envelope components.