What is a Thermal Bridge?

Source: Building Science Corporation Newsletter #49: Aqua Tower and Infra Red by Fluke Corp

A thermal bridge is an area of extreme heat transfer caused either by a conductive material crossing through an insulation layer or a geometric transition in the thermal boundary.  Commonly found at studs, plumbing penetrations, steel beams, and balconies, thermal bridges can significantly reduce the overall R-Value of an assembly.  Passive House buildings are thoughtfully designed to eliminate thermal bridges, thereby mitigating energy loss.

A commonly used example showing the extreme heat transfer through cantilevered balconies on the Aqua tower in Chicago.

Super insulated wall assemblies not only reduce energy consumption, but they greatly increase the long-term durability of the homes envelope, by maintaining consistent surface temperatures through the assembly, which greatly if not completely eliminates the possibility of mold formation.