Most homeowners are shocked when their Energy Performance Certificate (EPC) rating comes back lower than expected. While some issues are obvious — like old boilers or lack of insulation — many score-dropping factors are subtle, hidden, and easy to overlook. EPC assessors follow a strict methodology, and even small inefficiencies can significantly impact your rating.
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1. Poor or Missing Insulation (The #1 EPC Score Killer)
Nothing lowers an EPC rating faster than inadequate insulation. Assessors check insulation depth, coverage, and material quality. Common problems include:
Loft insulation below 270mm
Missing cavity wall insulation
Solid walls with no insulation layer
Gaps or patchy insulation from previous work
Without proof or visible insulation, assessors must assume the worst-case scenario.
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2. Outdated or Inefficient Heating Systems
Your heating system contributes heavily to your EPC score. Assessors quickly flag:
Non-condensing boilers
Old radiators with no TRVs
Manual thermostats with no zone controls
Immersion heaters without insulation
Upgrading your boiler or installing smart heating controls can dramatically increase your score.
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3. Single Glazing or Poor Window Seals
Even if the rest of your home is efficient, old or poorly sealed windows heavily reduce your rating. Assessors look for:
Single glazed windows
Failed double-glazing units (condensation inside panes)
Draughty frames
No trickle vents
Switching to energy-efficient glazing can boost comfort and your EPC score.
4. Inefficient Lighting Throughout the Home
Lighting may seem minor, but if more than half your home uses halogen or incandescent bulbs, the EPC score drops noticeably.
LED lighting is one of the cheapest, fastest EPC improvements.
5. Uninsulated Hot Water Cylinders & Old Pipework
Another major issue flagged immediately:
Bare hot water cylinders
Cylinders with thin or damaged insulation jackets
Exposed, uninsulated pipework
These cause heat loss, drive energy bills up, and reduce EPC efficiency.
6. Lack of Documentation for Upgrades
One of the most common (and frustrating) reasons for a low EPC score:
Homeowners forget to show the assessor proof of improvements.
This includes:
Loft insulation certificates
Boiler installation documentation
Solar panel system details
Window or door replacement invoices
Without proof, assessors must default to standard assumptions — often lower than reality.
7. Air Leakage and Draught Problems
Assessors routinely flag unseen air leaks that allow heat to escape:
Gaps around doors and windows
Cracks in walls
Draughty fireplaces
Uninsulated loft hatches
Draught-proofing is a low-cost solution that provides noticeable EPC improvements.
8. Old Construction Features in Older Homes
Older homes often lose points because they contain original features that aren’t energy-efficient:
Solid walls
Suspended timber floors
Uninsulated roofs
Inefficient chimneys
While upgrading these can be expensive, even partial improvements can boost a property’s rating.
How to Avoid a Low EPC Rating
To ensure your score reflects your home’s true energy efficiency:
Prepare documentation
Fix small inefficiencies like draughts, lighting, and insulation gaps
Upgrade heating controls
Consult with a professional assessor before your EPC appointment
If you’re ready to schedule your assessment, book here:
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For any questions or guidance, contact us directly:
https://epcrate.co.uk/contact-us-epc-services-london/
Conclusion
A low EPC score rarely comes from one major fault — it’s usually a combination of overlooked issues. Assessors immediately flag missing insulation, old heating systems, poor glazing, and lack of documentation. Addressing these areas ahead of your assessment can significantly increase your EPC rating, reduce energy bills, and improve your property’s value.
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