A localized point in a building's envelope - a balcony slab, a steel beam through insulation - where heat escapes much faster than through the surrounding construction. A thermal bridge undermines an otherwise well-insulated wall or roof assembly, showing up as a cold spot, a condensation risk, and a real gap between a design's calculated and actual energy performance. Detailing insulation continuity around structural penetrations - and modeling those junctions accurately in Revit - is what a thermal bridging assessment actually checks.