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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.
Ok thanks for posting. Do you have a manual on how to avoid thermal bridging at the parapet? We are looking to insulate the walls of the back of the house, but the roof is near flat, so I would like to understand how it can be finished off at the top.
Hi Simon there are ways to do this to minimise cold bridging but some of the options could be quite expensive. For example you can use coping stones or you can extend the roof profile so the insulation buts up against the roof line.
If you go to the EWI Pro system designer website they will have more information on this subject.
I have had external wall insulation installed and have noticed mould form on top of the back bedroom wall – the insulation I belive is on the other side. Has anyone else experienced this? I spoke to the installer and he said it could be something to do with the loft insulation I also had installed. Any help, much appreciated.
How can I prevent cold bridging if I need to put a screw into a wall – does the rawlplug prevent cold bridging occurring or are there special plugs that prevent this from occurring. Thoughts would be useful as we have just had cavity wall insulation injected into our cavity and I need to put up a washing line, but don’t want to get condensation forming on the inside wall where a new cold spot appears because of the cold bridging.
Thermal bridging is critically important. I am glad you are making people aware of it.