How Thermal Bridging Affects Building Performance

As the UK continues to focus on energy efficiency and reducing carbon emissions, improving the performance of existing buildings has become a priority. One of the most critical, yet often overlooked, factors influencing building performance is thermal bridging.

Understanding what thermal bridging is, how it affects energy efficiency, and how to mitigate it is essential for homeowners, designers, and retrofit professionals working under PAS2035:2023 standards. This article explores the concept in detail and provides practical guidance for ensuring your building achieves optimal thermal performance.

What is Thermal Bridging?

A thermal bridge occurs when there is a break or weakness in a building’s insulation layer, allowing heat to pass through more easily than surrounding materials. These bridges create paths of least resistance for heat flow, often around structural elements, junctions, or openings.

Common areas where thermal bridging occurs include:

• Junctions between walls and floors or roofs

• Around window and door frames

• At wall-to-wall or wall-to-roof intersections

• Around steel beams or concrete lintels

While insulation may cover most of the building envelope, thermal bridges can significantly reduce its effectiveness, leading to higher heat loss, increased energy bills, and poor occupant comfort.

Why Thermal Bridging Matters

Thermal bridging affects building performance in several ways:

1. Increased Heat Loss
   Even small thermal bridges can account for a substantial proportion of heat loss. This reduces overall energy efficiency and can compromise the savings achieved through other retrofit measures like insulation or upgraded heating systems.

2. Condensation Risk
   Thermal bridges create cooler spots on interior surfaces. When warm, moist air comes into contact with these surfaces, condensation can occur. Persistent condensation may lead to mould growth, damp issues, and structural damage over time.

3. Reduced Comfort
   Occupants may experience cold spots, drafts, or uneven heating in rooms affected by thermal bridging. This can make living spaces less comfortable, even in well-insulated homes.

4. Impact on PAS Compliance and EPC Ratings
   Under PAS2035:2023, thermal bridging must be assessed and mitigated in retrofit projects. Unaddressed bridges can reduce the energy performance rating of a property, affecting compliance and eligibility for schemes such as ECO4 or government-backed retrofit funding.

Identifying Thermal Bridges

Accurate identification is the first step in addressing thermal bridging. Several methods are commonly used:

• Visual Inspection: Look for junctions between structural elements, corners, and areas around windows and doors.

• Thermal Imaging (Infrared Cameras): These cameras can detect temperature differences across surfaces, highlighting potential thermal bridges.

• Building Modelling Software: Tools like PASHUB or dynamic simulation software can predict heat flow and identify areas of concern before installation.

By identifying thermal bridges early, retrofit teams can plan mitigation measures during the design phase rather than addressing problems after installation.

How Thermal Bridging Affects Retrofit Projects

Thermal bridging is particularly relevant in retrofit projects, where new measures are added to existing structures. Without careful planning, retrofits may unintentionally create new thermal bridges or fail to address existing ones.

Some common retrofit-related scenarios include:

• Installing wall insulation that doesn’t fully cover junctions, leaving gaps at floors or ceilings.

• Adding external cladding without addressing bridging at window or door reveals.

• Retrofitting new heating systems without improving the building envelope first (fabric-first approach).

Failure to address these issues can compromise the performance of all other energy-efficiency measures.

Mitigating Thermal Bridging

Effective mitigation requires a combination of design, materials, and installation practices.

1. Design Considerations

• Ensure insulation is continuous across the building envelope.

• Pay special attention to junctions, corners, and penetrations.

• Incorporate thermal breaks where structural elements (like steel beams) penetrate insulation layers.

2. Material Selection

• Use high-performance insulation materials with low thermal conductivity.

• Specify insulated window and door frames where possible.

• Consider aerated blocks or thermal break pads for structural elements.

3. Proper Installation

• Ensure installers follow PAS2030:2023 standards.

• Avoid gaps, compression, or misalignment of insulation.

• Perform site inspections to verify that thermal continuity is maintained.

At Armstrong Eco Works, our team combines PAS2035-compliant design and coordination with expert oversight during installation to minimise thermal bridging and ensure maximum energy efficiency.

Thermal Bridging and Building Regulations

Thermal bridging is not just an efficiency concern; it’s also a regulatory requirement. UK building regulations set U-value targets and require measures to reduce heat loss through bridges.

Retrofit projects must:

• Comply with PAS2035:2023 guidance for junctions and detailing

• Document thermal bridging calculations for all structural elements

• Ensure that final energy performance aligns with predicted EPC ratings

Addressing thermal bridging proactively ensures regulatory compliance, improves building comfort, and protects long-term structural integrity.

The Role of PAS2035 in Managing Thermal Bridging

PAS2035:2023 emphasises a whole-house approach, ensuring that thermal bridging is considered at every stage of the retrofit process:

1. Retrofit Assessment: Identify potential thermal bridges and assess risk areas.

2. Design Stage: Integrate mitigation measures into the overall retrofit plan.

3. Installation Stage: Ensure continuity of insulation and proper execution by PAS2030-accredited installers.

4. Post-Installation Verification: Conduct site inspections and testing to confirm thermal performance.

This structured process minimises the likelihood of overlooked bridging and ensures the retrofit delivers its intended energy savings.

Benefits of Addressing Thermal Bridging

When thermal bridging is properly addressed, buildings experience:

• Lower energy bills due to reduced heat loss

• Increased occupant comfort with fewer cold spots

• Lower risk of condensation and mould

• Improved EPC ratings and compliance with PAS2035

• Long-term durability and reduced maintenance costs

Effectively managing thermal bridges is therefore a cost-effective investment that enhances both building performance and occupant wellbeing.

Conclusion

Thermal bridging is a subtle but significant factor affecting the energy efficiency, comfort, and longevity of buildings. In retrofit projects, failure to identify and address thermal bridges can undermine the benefits of other energy-saving measures, leading to higher bills, poor comfort, and non-compliance with PAS2035:2023.

By taking a proactive, whole-house approach, using detailed assessments, PAS2035-compliant design, and PAS2030-certified installation, thermal bridging can be effectively minimised.

At Armstrong Eco Works, we specialise in Retrofit Assessments, Consultancy, and PAS-compliant project coordination. Our expertise ensures that every project not only meets regulatory standards but also delivers lasting energy performance and comfort for building occupants.

Get in touch with Armstrong Eco Works today to discuss how we can help you identify and mitigate thermal bridging in your next retrofit project.