When homeowners think about Energy Performance Certificate (EPC) ratings, the focus often falls on insulation, windows, and heating systems. However, one of the most overlooked factors is air tightness — the degree to which a building prevents unwanted air leakage. Air tightness plays a critical role in determining energy efficiency, comfort, and your EPC score.
What is Air Tightness?
Air tightness refers to how well a building prevents uncontrolled airflow through gaps, cracks, and openings in the fabric of the property. Poor air tightness leads to:
Heat escaping through walls, floors, roofs, and windows
Increased energy demand for heating or cooling
Drafts and uneven indoor temperatures
Higher carbon emissions
During an EPC assessment, the degree of air leakage influences the calculated energy use and overall rating.
How Air Tightness Impacts EPC Ratings
1. Energy Loss Through Gaps
Even a well-insulated home can lose significant heat if air leaks are present. For example:
Draughty windows, doors, or skirting boards
Gaps around loft hatches or pipework
Cracks in walls or floors
Impact on EPC: Increased heat loss leads to lower SAP (Standard Assessment Procedure) scores, which reduces the EPC rating.
2. Heating Efficiency
Homes with poor air tightness require more heating to maintain comfortable temperatures.
Upgrading heating systems without improving air tightness may not yield the expected EPC improvement.
3. Ventilation Balance
While airtight homes retain heat better, ventilation must be adequate to prevent damp, condensation, and poor indoor air quality. Proper mechanical or passive ventilation is essential for high-performing EPCs.
Ways to Improve Air Tightness
Seal gaps around windows, doors, and skirting boards
Insulate loft hatches and roof access points
Use draught-proofing around pipes and utility entries
Ensure proper installation of insulation and glazing
Combine with controlled ventilation systems to maintain air quality
Improving air tightness can enhance comfort, lower energy bills, and contribute to a higher EPC rating.
Professional EPC Assessment with Urgent EPC
At Urgent EPC, we provide thorough EPC surveys that take air tightness into account, along with insulation, heating, and renewable energy systems. Our assessors ensure your certificate accurately reflects your property’s efficiency.
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Contact Us to schedule your EPC today.
Final Thoughts
Air tightness may be hidden from plain sight, but its impact on your EPC rating is significant. By addressing drafts, sealing gaps, and combining with proper insulation and heating, homeowners can improve comfort, reduce energy bills, and boost their EPC scores — a smart investment for compliance and long-term efficiency.
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