When it comes to improving your Energy Performance Certificate (EPC) rating, many homeowners focus on insulation, heating systems, or double glazing. However, one frequently overlooked factor is thermal bridging—a phenomenon that can significantly reduce your property’s energy efficiency and EPC score.

Understanding thermal bridging, how it is assessed, and the practical steps you can take to minimise its impact can make a real difference in your EPC rating. Our EPC Assessors in London regularly identify thermal bridging issues during assessments:
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1. What Is Thermal Bridging?

Thermal bridging occurs when heat escapes through areas of a building that are less insulated or more conductive than the surrounding material. Essentially, it’s a “shortcut” for heat to leave the building, bypassing insulation layers.

Common thermal bridges include:

  • Junctions between walls and floors

  • Corners of rooms

  • Around windows and doors

  • Roof-to-wall connections

  • Structural elements like steel beams or concrete lintels

Even with excellent insulation, thermal bridges can create cold spots, condensation, and energy inefficiency, lowering EPC performance.


2. How Thermal Bridging Affects EPC Ratings

EPCs measure theoretical energy efficiency based on the building’s fabric, heating systems, and energy controls. Thermal bridging impacts EPC scores because:

  • Heat loss through thermal bridges increases calculated energy demand

  • The property is considered less energy-efficient

  • Points are lost in building fabric calculations, which can affect the overall EPC band

In some cases, a property with good insulation and heating may still have a moderate EPC score due to unnoticed thermal bridging.


3. Common Causes of Thermal Bridging

Understanding the typical causes helps homeowners address the problem before an EPC assessment:

a) Poor Construction Details

  • Uninsulated lintels above windows

  • Gaps at floor-to-wall junctions

  • Concrete balconies or steel beams without thermal breaks

b) Renovations and Extensions

  • Improperly insulated extensions

  • Junctions between old and new building fabric

  • Inconsistent insulation thickness

c) Structural Features

  • Exposed masonry

  • Chimneys

  • Party walls in flats or terraced houses


4. Identifying Thermal Bridging

Thermal bridging can be difficult to spot without professional guidance. Common signs include:

  • Cold spots on walls or ceilings

  • Condensation or mould in corners

  • Uneven heating in rooms

  • Drafts near structural elements

For accurate identification, EPC assessors use standardised software calculations or may recommend a thermographic survey to visualise heat loss.


5. Minimising Thermal Bridging

Addressing thermal bridging can have a direct and measurable impact on your EPC score. Effective strategies include:

  • Improved insulation detailing: Ensure continuous insulation at junctions

  • Thermal breaks: Insert insulating materials between conductive elements (e.g., steel or concrete)

  • Sealing gaps: Use draught-proofing at junctions and openings

  • High-performance window installation: Ensure frames and edges are well insulated

  • Professional guidance for extensions/retrofits: Integrate insulation properly with existing structures

These measures reduce heat loss, prevent condensation, and boost EPC points.


6. Thermal Bridging and Property Value

A home with visible thermal bridging may suffer from:

  • Higher energy bills

  • Cold spots and discomfort

  • Damp or mould issues

Correcting thermal bridges not only improves your EPC but also enhances comfort, reduces utility costs, and protects property value.


7. Strategic Planning for EPC Improvements

If your goal is to raise your EPC band, consider thermal bridging as part of a holistic improvement plan:

  1. Review current insulation and building fabric

  2. Identify potential thermal bridges in structural elements

  3. Implement insulation improvements and thermal breaks

  4. Ensure heating systems and controls are efficient

  5. Schedule an EPC re-assessment once all upgrades are complete

👉 Book an EPC assessment to see how thermal bridging affects your rating:
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8. Key Takeaways

  • Thermal bridging is heat loss through poorly insulated or conductive elements

  • It reduces EPC ratings even in homes with good insulation and heating

  • Common causes include construction details, renovations, and structural elements

  • Mitigation strategies include thermal breaks, improved insulation, and draught-proofing

  • Addressing thermal bridging improves energy efficiency, comfort, and property value

By proactively tackling thermal bridging, homeowners can maximise their EPC score and protect long-term property value.


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