Thermal Bridges in UK Homes - Spot & Prevent Heat Loss

Thermal bridges are small and often overlooked but they can badly affect the energy efficiency and comfort of your home. These hidden weak spots in the building envelope allow heat to escape much faster than through properly insulated areas, increasing your energy bills and raising the risk of condensation and dampness. 

In this blog, ‘Thermal Bridges in UK Homes – Spot & Prevent Heat Loss’ we break down exactly what thermal bridges are, where they commonly occur, and why they’re such a problem in UK homes.

Whether you're considering external wall insulation for your home or just want to learn more, this guide will give you everything you need to understand thermal bridging.

What Are Thermal Bridges? 

Thermal Bridges - also known as cold bridges - are specific areas in a building envelope where heat escapes more easily than through the surrounding materials. These weak points typically occur where insulation is missing, thin or interrupted by material with high thermal conductivity like metal or concrete. When heat flows out more quickly through these spots, it can lead to cold patches indoors, increased energy usage, and higher heating bills.

In fact, thermal bridges can account for up to 30% of total heat loss in poorly insulated buildings. In the long term, thermal bridges can also cause condensation and damp problems, making them a serious concern for comfort of the occupants and structural integrity of the property.

Types of Thermal Bridges

Thermal bridges can take several forms, depending on how and where heat escapes through the building envelope. The main types include:

Linear Thermal Bridges 

These occur along lines where building elements meet—for example, at wall-to-floor junctions, roof connections, or around windows and doors. They are often caused by interruptions in insulation or poor detailing during construction.

Linear bridges are measured using a psi (Ψ) value, which calculates heat loss per metre.

Point (Punctual) Thermal Bridges

These happen at small, specific points where insulation is penetrated by a material with high thermal conductivity—like metal fixings or wall ties.

Point bridges are measured using a chi (χ) value, which calculates heat loss at individual spots.

Service and Geometrical Thermal Bridges

Some thermal bridges are caused by the design or use of the building, rather than just materials.

• Service Penetrations: Pipes, cables, and gas meter boxes that pass through insulation layers can create localised weak points.
  
  
• Geometrical Bridges: Occur at corners, edges, or junctions where the building’s shape causes more heat loss due to increased surface area.

Many thermal bridges are avoidable with professional installation of insulation systems.

How Are Thermal Bridges Identified?

Identifying thermal bridges is a key step in improving a building’s energy efficiency. These hidden heat-loss points can be tricky to spot without the right tools or knowledge, but there are a few reliable methods used by professionals.

1. Thermal Imaging (Infrared Thermography)

The most accurate and efficient way to detect thermal bridges is with a high-resolution thermal imaging camera. These cameras visually display surface temperature differences across walls, windows, and other parts of the building. Areas with lower temperatures often indicate spots where insulation is missing or ineffective.

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2. Visual Inspection

In some cases, thermal bridges can be spotted with the naked eye. Common signs include:

• Damp patches or mould growth on interior walls
  
  
• Discolouration or peeling paint
  
  
• Condensation build-up around windows, doors, and structural joints

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3. Condensation Patterns

Persistent condensation in specific areas of a home, especially around structural junctions or where insulation is likely interrupted, may also signal the presence of thermal bridges.

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Why Should Thermal Bridges Be Avoided?

Thermal bridges are often overlooked, especially during poorly planned insulation work. However, these small problem areas can have a big impact on energy performance, comfort, and long-term health of the building. They can lead to: 

• Higher Energy Bills: Thermal bridges allow heat to escape from your home more quickly, meaning your heating system has to work harder to maintain a comfortable indoor temperature. This increased energy demand leads to noticeably higher heating bills, a cost that adds up over time.
• Reduced Thermal Comfort: Cold spots created by thermal bridges can make rooms feel draughty or unevenly heated. These areas often lead to condensation forming on walls, especially in winter. Persistent moisture can cause mould growth, which poses serious health risks like allergies and respiratory issues.
• Structural Damage Over Time: When moisture builds up within a wall and freezes, it expands, potentially damaging building materials. Over time, this cycle of damp and freezing can weaken structural elements and lead to costly repairs.
• Sustainability and Lower Emissions: Homes that retain heat more effectively use less energy, which reduces carbon emissions. Tackling thermal bridges is a smart step toward building a more energy-efficient, environmentally friendly home.

How to Avoid Thermal Bridges During External Wall Insulation (EWI)

Thermal bridging is a common issue in solid-wall homes, but it can be significantly reduced with proper installation of external wall insulation. While thermal bridges can occur due to design elements, many are caused by poor installation practices.

Here’s how thermal bridging can be minimised during EWI installation:

• Continuous Insulation Layer - One of the most effective ways to avoid thermal bridging is by applying insulation in a continuous, uninterrupted layer around the entire external envelope. Gaps or interruptions, especially around corners or junctions can create cold spots that allow heat to escape. According to Approved Document L of the UK Building Regulations, continuous insulation and the reduction of thermal bridges are essential for meeting modern energy efficiency standards.
  
  
• Precise Detailing Around Openings - Window and door reveals, pipe penetrations, and meter boxes are key risk areas. To avoid cold bridging here, insulation should be carefully cut, fitted, and sealed.
  
  
• Attention to Wall-Floor and Wall-Roof Junctions - Thermal bridges often form at the wall/floor and wall/roof junctions. These areas should be detailed to ensure insulation continues seamlessly, without thermal breaks.
  
  
• Use of Low-Thermal Conductivity Fixings - Mechanical fixings can create point thermal bridges. To reduce this, installers often use low-conductivity plastic anchors and thermal break washers, especially when fixing insulation boards to solid walls.

Preventing Heat Loss Through Smart Detailing

Thermal bridges may be small in size, but their impact on energy efficiency, comfort, and even the structural integrity of a building can be significant. The good news is that, with careful planning and attention to detail, most thermal bridges can be avoided during external wall insulation installation.

Considering EWI? Make sure the work is carried out by experienced professionals who understand how to prevent thermal bridging. A well-installed system not only saves energy but keeps your home warmer, drier, and more comfortable for years to come.

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