Thermal bridges are very common in old houses or houses with insufficient insulation. The affected part of the construction results to a significantly higher heat transfer than the surrounding materials resulting in an overall reduction in thermal insulation of construction. Partially insulated building elements are responsible for up to 35% of thermal losses and increased condensation that leads to mold growth.
Thermal bridges can be classified into three main types (Leeds Beckett University: Low Carbon Housing Learning Zone):
- Repeating or quasi-homogeneous thermal bridges usually follow a regular pattern and are evenly distributed over an area of the thermal envelope
- Non-repeating or linear thermal bridges are often caused by discontinuities in the thermal envelope and occur at a specific point in the construction
- Geometrical thermal bridges are a result of the geometry or shape of the thermal envelope
The most common parts of a construction where the thermal bridges can occur are:
- The parts of the building envelope that are exposed to the external environment and have different thermal conductivity
- The parts where a change in the thickness of the fabric occurs
- The wall-floor-ceiling junctions of the building where there is a difference between internal and external areas
To avoid thermal bridging you should provide your house with enough insulation at the affected parts such as:
- Concrete balconies that extend the floor slab through the building envelope.
- Areas around glazing, window frames and rooflights
- Metal ties in masonry cavity external walls
- Ceiling joists in cold pitched roofs
- Ground floor joists in an insulated suspended timber ground floor
- Timber studwork and I-beams in timber frame constructions
- Mortar joints in an insulating block inner leaf
- Areas round loft hatches
- Wall/ roof junctions or wall/ floor junctions
- At the corner of an external wall
- Junctions between adjacent walls
There are many strategies and methods that the builder should follow to avoid thermal bridges:
- Apply a continuous layer of insulation around the external walls of you house such as expanded polysteryne or mineral wool insulation.
- By adding insulation at the outside corner of your building where the walls and floor are connected
By reducing thermal bridges you will have saved a great amount of heat losses and energy needs of your home resulting in reduced energy bills and increased building lifespan.