When it comes to Energy Performance Certificates (EPCs), insulation, heating systems, and windows often get most of the attention. However, one critical yet often overlooked factor is building airtightness. Even with top-quality insulation and modern heating, poor airtightness can reduce energy efficiency and prevent your property from achieving a high EPC rating.

At Urgent EPC, we regularly assess properties where airtightness issues undermine energy performance. Understanding this factor can help homeowners, landlords, and property developers meet EPC targets more effectively.

What Is Building Airtightness?

Building airtightness refers to how well a property prevents uncontrolled air leakage through the building envelope — including walls, floors, roofs, windows, doors, and joints.

• Poor airtightness allows warm air to escape in winter and cool air in summer.

• This leads to higher energy consumption, uneven temperatures, and increased costs.

• EPC assessors account for uncontrolled air leakage when calculating energy efficiency ratings.

How Airtightness Impacts EPC Ratings

1. Increased Energy Consumption
   Even small gaps or cracks allow heat to escape, forcing heating systems to work harder. This higher energy demand is reflected in the EPC calculation.

2. Lower EPC Band
   Properties with uncontrolled air leakage are rated less energy-efficient, even if insulation and heating systems are high-quality.

3. Interaction with Other Factors
   Airtightness works hand-in-hand with insulation. High-quality insulation cannot reach its full potential if warm air leaks through gaps, leading to misleading EPC assumptions.

4. Thermal Comfort and Moisture Control
   Poor airtightness can create drafts, cold spots, and condensation issues — factors that indirectly influence EPC outcomes.

Common Causes of Poor Airtightness

• Gaps around doors, windows, and skirting boards

• Penetrations for plumbing, electrical wiring, and ventilation

• Roof and loft hatch leaks

• Poorly sealed extensions or renovations

• Inefficient or unsealed ductwork in mechanical systems

How to Improve Airtightness

• Seal gaps and cracks using high-quality sealants, foam, or gaskets

• Install airtight doors and windows with proper weatherstripping

• Check roof and loft access points for leaks

• Use airtightness membranes in new builds or extensions

• Professional testing: Blower door tests identify leaks that may not be visible

How Urgent EPC Can Help

At Urgent EPC, our expert assessors:

• Evaluate building airtightness as part of a comprehensive EPC assessment

• Provide actionable advice to reduce heat loss and maximise EPC ratings

• Offer Same-Day EPC services for urgent compliance needs

• Deliver clear pricing plans and guidance for homeowners, landlords, and property managers

Conclusion

Building airtightness is a crucial factor in achieving high EPC ratings. By addressing gaps, leaks, and unsealed penetrations, homeowners and landlords can improve energy efficiency, reduce running costs, and achieve compliance with energy regulations.

For professional EPC assessments and guidance on maximising your property’s airtightness, contact Urgent EPC today.