Thermal Bridge

A localised area of a building's envelope with significantly worse thermal performance than the surrounding elements - for example, a steel beam penetrating the insulation layer, a concrete lintel, or a window frame. Thermal bridges create localised cold spots that can cause condensation and mould and reduce overall energy efficiency. Psi (ψ) values quantify the heat loss at linear junctions (e.g. wall-floor or wall-roof).