What Is Thermal Bridging? Causes, Prevention and Building Regulations Explained
Thermal bridging is one of the most overlooked factors affecting a building's energy performance. Even if walls, floors and roofs are well insulated, poorly detailed junctions can allow heat to escape, reducing efficiency and increasing the risk of condensation.
As energy efficiency standards continue to tighten, understanding thermal bridging has become essential for architects, contractors, self-builders and retrofit specialists.
What Is Thermal Bridging?
A thermal bridge is an area of a building where heat passes through the building envelope more easily than the surrounding construction.
This usually occurs where insulation is interrupted by a material with a higher thermal conductivity, creating a path for heat to escape. As a result, the internal surface temperature in these areas can be lower than elsewhere in the building.
Common examples include:
- Window and door reveals
- Floor-to-wall junctions
- Wall-to-roof connections
- Structural steelwork
- Concrete lintels
- Balconies
- Service penetrations
- Timber or steel framing junctions
Although these areas may appear small, collectively they can have a significant impact on the overall thermal performance of a building.
What Causes Thermal Bridging?
Thermal bridging is often the result of design, construction or installation details that interrupt the continuous insulation layer.
Typical causes include:
Structural Elements
Materials such as steel and concrete conduct heat much more readily than insulation. If these elements are not carefully detailed, they can create significant thermal bridges.
Incomplete Insulation
Missing or poorly installed insulation around junctions, openings or service penetrations leaves areas vulnerable to heat loss.
Poor Junction Detailing
Where walls meet floors, roofs or windows, gaps in the thermal envelope can occur if construction details are not carefully designed and installed.
Service Penetrations
Pipes, cables and ductwork passing through external walls must be carefully sealed to maintain both airtightness and thermal performance.
Why Does Thermal Bridging Matter?
Thermal bridging affects much more than energy efficiency.
Heat escaping through thermal bridges can lead to:
- Increased heating and cooling costs
- Reduced building energy performance
- Colder internal surface temperatures
- Surface condensation
- Mould growth
- Reduced occupant comfort
- Greater risk of fabric deterioration over time
Addressing thermal bridging helps create buildings that are warmer, healthier and more comfortable to occupy.
How Can Thermal Bridging Be Prevented?
Reducing thermal bridging begins during the design stage and continues throughout construction.
Good practice includes:
Maintain Continuous Insulation
The insulation layer should remain continuous around the entire building envelope wherever possible.
Pay Attention to Junctions
Wall-to-floor, wall-to-roof and window junctions should be designed to minimise heat loss while maintaining continuity of insulation and airtightness.
Seal Penetrations Properly
Service penetrations should be carefully detailed using appropriate airtight products to prevent unnecessary heat loss and uncontrolled air leakage.
Use Quality Installation Practices
Even the best design can be compromised by poor workmanship. Careful installation is essential for achieving the intended thermal performance.
Thermal Bridging and Airtightness
Although thermal bridging and airtightness are different aspects of building performance, they work closely together.
A building with excellent insulation but poor airtightness can still lose significant amounts of heat through uncontrolled air leakage.
Likewise, well-designed airtightness systems help maintain the continuity of the building envelope, reducing air leakage around junctions and penetrations while supporting overall energy performance.
Thermal Bridging and Building Regulations
The 2022 updates to Approved Document L place greater emphasis on improving the energy efficiency of buildings.
Designers and contractors are expected to minimise thermal bridging through careful detailing and improved construction methods as part of achieving compliance.
Reducing thermal bridging helps contribute towards:
- Improved fabric performance
- Lower operational energy use
- Reduced carbon emissions
- Better SAP calculations
- Improved occupant comfort
- Compliance with modern Building Regulations
As buildings become more energy efficient, attention to junction detailing and construction quality becomes increasingly important.
Supporting Better Building Performance
Creating a high-performing building envelope requires more than insulation alone.
Carefully detailing junctions, maintaining airtightness and ensuring continuity around service penetrations all contribute towards reducing unwanted heat loss.
Products such as Passive Purple, airtight tapes and reinforced detailing membranes can help create continuous airtight layers around complex junctions where traditional sheet membranes may be more difficult to install.
Whether you're working on a new-build or retrofit project, reducing thermal bridging is an important step towards creating more comfortable, durable and energy-efficient buildings. Contact us today for help with your build.