Adding an extension to your home can create extra space and increase property value, but did you know it can also impact your Energy Performance Certificate (EPC) rating? Whether you’re building a loft conversion, side extension, or rear addition, understanding how home extensions affect energy efficiency is essential to maintaining or improving your EPC.

Learn more about our expert EPC services on our About Us page.

Why Extensions Affect EPC Ratings

EPC ratings measure the energy efficiency of a property based on:

  • Insulation quality of walls, floors, and roofs

  • Heating and hot water systems

  • Windows and doors

  • Ventilation and air leakage

When you add an extension, the new part of the property can either improve or reduce your overall rating, depending on how well it is built and insulated.

Key Factors That Influence EPC Scores for Extensions

1. Insulation and Thermal Performance

  • Poorly insulated walls, floors, or roofs in extensions create heat loss.

  • Ensure cavity walls are properly filled and loft or flat roofs are insulated to current standards.

2. Windows and Doors

  • Adding large glass panels or sliding doors without energy-efficient glazing can reduce EPC ratings.

  • Use double or triple glazing and Low-E glass to maintain efficiency.

3. Heating and Hot Water Integration

  • Extensions need to tie into the existing heating system efficiently.

  • Consider zoned heating, thermostatic radiator valves (TRVs), or smart controls to minimise energy loss.

4. Ventilation

  • Modern extensions may include extractor fans or MVHR systems.

  • Poorly installed ducting or uninsulated systems can reduce energy efficiency.

5. Renewable Energy Considerations

  • Adding solar panels, heat pumps, or other green technology to extensions can offset energy loss.

  • Consider these solutions during the design phase for maximum EPC impact.

For professional guidance, check our EPC Services – Assessors London page.

Tips for Maintaining or Improving EPC Ratings During Extensions

  • Plan insulation and glazing from the start

  • Use energy-efficient materials throughout construction

  • Avoid unnecessary draughts or thermal bridges

  • Integrate heating and ventilation systems efficiently

  • Consult a certified Domestic Energy Assessor (DEA) before and after the extension

Why Professional EPC Assessment is Crucial

A certified EPC assessor can:

  • Evaluate how your extension affects the property’s overall energy performance

  • Provide advice on cost-effective improvements

  • Ensure compliance for sales or rentals

Book an assessment through our Booking Page to get accurate ratings and recommendations.

Contact Us for EPC Guidance

Have questions about your home extension and EPC?
Reach out via our Contact Page for expert advice and professional support.

Email:info@epcrate.co.uk

Phone:020 34884142