When assessing a property’s Energy Performance Certificate (EPC) rating, the choice of roofing material is a key factor. While standard materials like clay tiles, concrete, and slate are commonly accounted for in EPC calculations, properties that use non-standard roofing materials—such as metal, thatch, green roofs, or modern composites—can present unique challenges and opportunities.

1. Why Roofing Materials Matter in EPC Assessments

The roof is one of the largest sources of heat loss in a building. EPC ratings consider:

  • Thermal performance of the roof covering and insulation.

  • Durability and airtightness, which influence long-term efficiency.

  • Impact on heating and cooling demand, especially in modern builds.

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2. Types of Non-Standard Roofing and Their EPC Impacts

✅ Metal Roofing (Steel, Zinc, Aluminium)

  • Highly durable and reflective, helping with summer cooling.

  • Can increase winter heating demand if not paired with good insulation.

✅ Thatch Roofs

  • Naturally insulating and breathable.

  • May struggle with airtightness compared to modern materials.

✅ Green or Living Roofs

  • Improve insulation and reduce heat loss.

  • Offer excellent EPC benefits if properly installed.

✅ Composite or Synthetic Roofing

  • Variable performance depending on the product.

  • Often designed for better insulation, but EPC impact depends on tested values.

3. Challenges for EPC Assessors

Homes with non-standard roofs may create assessment issues, including:

  • Limited SAP data – standard EPC software may not always have reference values for unique materials.

  • Variable performance – efficiency depends heavily on installation quality.

  • Ventilation considerations – some materials require different airflow strategies to avoid moisture problems.

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4. Improving EPC Scores with Non-Standard Roofs

Property owners can boost EPC ratings by:

  • Ensuring adequate insulation beneath non-standard materials.

  • Using vapour control layers to improve airtightness.

  • Combining roofing materials with renewable systems, such as solar PV on metal or composite roofs.

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5. Why Professional EPC Advice is Essential

Because non-standard roofs can complicate EPC modelling, a professional assessor is essential. They will:

  • Identify correct thermal values for unusual roofing.

  • Recommend upgrades compatible with your chosen material.

  • Ensure the EPC rating reflects real-world performance.

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Conclusion

Non-standard roofing materials can positively or negatively affect EPC ratings depending on insulation, airtightness, and installation quality. While some, like green roofs, may improve efficiency, others may require additional insulation measures to achieve strong EPC scores. A tailored EPC assessment ensures that your property’s unique roofing is properly evaluated for energy performance.