Thermal bridge

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A thermal bridge, also called a cold bridge or heat bridge, is an area of an object (frequently a building) which has a significantly higher heat transfer than the surrounding materials resulting in an overall reduction in thermal insulation of the object or building. Thermal bridges occur in three ways, through: materials with higher thermal conductivity than the surrounding materials, penetrations of the thermal envelope, and discontinuities or gaps in the insulation material.

Thermal bridging in buildings reduces energy efficiency and can allow condensation (moisture) and thermal comfort problems. Condensation can result in indoor air quality problems and building deterioration.

Thermal bridging is prevented by careful design applying materials to achieve a uniform thermal resistance such as thermal breaks and continuous insulation.

Low-energy buildings use a thermal insulation layer that carefully encloses the whole building without any missed area, which means no "holes" in the insulation. If there are, heat transfers significantly through any "hole", greatly reducing the whole system of insulation. Thermal bridges are characterized by multi-dimensional heat transfer, and therefore they cannot be adequately approximated by the one-dimensional models of calculation typically used in norms and standards for the thermal performance of buildings (U-values). Surface moisture due to condensation, typically occurring in such regions as floor-wall connections and window installations, as well as mold growth in humid environments can also be effectively prevented by means of multi-dimensional evaluation during planning and detail design.

Thermal bridges take places commonly in reinforced concrete exterior walls surrounding seismic columns, ring beams, lintels doors, reinforced concrete or steel frame beams, columns, reinforced concrete or metal roof in a small side ribs, and metal curtain wall glazing where the metal frame and window extrude to outside.

While thermal bridges exist in various types of building enclosures, two types show significant reduced R-value caused by thermal bridges, masonry and curtain wall.

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