Thermal bridges, also known as cold bridges, are weak points (or areas) in the building envelope which allow heat to pass through more easily. They occur where materials which are better conductors of heat are allowed to form a 'bridge' between the inner and outer face of a construction. Thermal bridges result in an overall reduction in. Often, the culprit is not just moisture from daily activities, but a structural issue known as cold bridging, or simply a cold spot on a surface where warm, moist air inside the property can condense. Condensation and mould formation can be caused by structural thermal bridges.