Since 15 June 2025, many property owners have been surprised to see relatively modern double-glazed windows described as “Average” — or even “Poor” — on their Energy Performance Certificate (EPC).
As a Chartered Surveyor and long-standing EPC practitioner, I can confirm this is not an error. It reflects a fundamental update to the EPC calculation methodology.
What Changed in June 2025?
The EPC software update tightened the criteria for glazing performance bands:
- “Good” is now largely reserved for triple glazing or high-performance modern systems with strong documented U-values.
- “Average” generally applies to post-2002 double glazing without confirmed enhanced performance data.
- “Poor” may now apply to older double glazing where age or specification cannot be evidenced.
Previously, many standard double-glazed units installed in the 2000s would automatically attract an “Average” or sometimes better narrative rating. The revised methodology better reflects current energy efficiency standards and the UK’s drive toward improved building fabric performance.
Why Documentation Matters
If a FENSA certificate or manufacturer’s specification confirming thermal performance is unavailable, assessors must rely on age bands. Without verifiable data, the software will not assume enhanced efficiency.
Does This Affect My EPC Rating?
In many cases, the overall EPC band (A–G) remains stable. However, glazing performance can influence your property’s score — particularly for landlords concerned about Minimum Energy Efficiency Standards (MEES) compliance.
If you’re selling, letting, or reviewing compliance, instruct an experienced provider.
For accurate advice and fast turnaround on your EPC, contact EPC Choice — trusted assessors since 2008 and consistently 5-star rated across the UK.