Most homeowners expect an EPC to pass smoothly—until the rating comes back surprisingly low. Beyond common issues, assessors frequently uncover hidden, unusual problems that dramatically reduce your property’s score. Understanding these rare factors can help you prepare before your next assessment through services like our certified team at EPC Assessors London.
1. Hidden Air Leaks You Never Knew Existed
Tiny gaps behind walls, floors, or extension joints create silent heat loss.
When these leaks are found during an EPC inspection, they almost always reduce your rating.
If you’re unsure whether your home has unseen energy leaks, booking a professional inspection early helps:
Try our fast appointment service here: Book EPC Online.
2. Insulation That Has Degraded Over the Years
Insulation that has compressed or become damp no longer performs at the level it should. Even homes that once had a good rating may fail unexpectedly if insulation has deteriorated.
If you’re not sure what your old insulation is worth today, read more about our assessment approach in About Us.
3. Structural Cold Bridges Causing Invisible Heat Loss
Many EPC failures come from “cold bridges”—parts of the home where heat escapes rapidly through:
Steel beams
Lintels
Uninsulated connection points
These structural issues are usually hidden, so they surprise homeowners during assessments.
4. Missing or Incorrect Documentation
Even if you’ve upgraded your home, failing to provide proof means the assessor must assume the worst-case scenario.
Missing confirmation of insulation, glazing, or renewable installations is one of the most common reasons for unexpected EPC results.
To avoid this, check pricing options and documentation requirements beforehand here:
EPC Pricing.
5. Outdated or Poorly Installed Heating Controls
A modern boiler alone cannot guarantee a good EPC score if:
TRVs are missing
Thermostats are in wrong locations
Programmers aren’t functioning
No smart controls are installed
Your heating controls influence your home’s efficiency more than many homeowners realise.
6. LED Bulbs Missing in Key Rooms
Leaving just a few halogen bulbs in bathrooms or kitchens can lower the overall score.
Switching all lighting to LEDs is one of the easiest ways to improve your EPC rating instantly.
7. Extensions and Loft Conversions Without Proper Insulation
Modern extensions, loft conversions, and conservatories often cause EPC surprises.
Even newly built additions sometimes lack adequate insulation, reducing the property’s overall performance.
Before planning upgrades or extensions, it helps to speak with an expert here:
Contact Our EPC Team.
8. Ventilation Issues That Cause Damp or Energy Loss
Blocked vents, non-working extractor fans, or excessive ventilation can lead to heat loss and condensation—both of which impact EPC scoring.
Assessors frequently find poorly designed airflow systems in older homes or renovated properties.
9. Solar Panels Not Logged or Certified Properly
Solar PV only improves an EPC rating if all documentation is available.
Missing MCS certificates or unregistered installation dates often lead to lower scores than expected.
10. Old Hot Water Cylinders Without Insulation Jackets
Many EPC failures involve outdated cylinders that lose heat rapidly.
Adding a jacket or upgrading the cylinder can quickly improve efficiency.
Recovering From an Unexpected EPC Fail
To raise your rating quickly:
✔ Upgrade insulation
✔ Fix draughts
✔ Install smart heating controls
✔ Prepare all documentation
✔ Re-book an up-to-date EPC evaluation
You can find trusted local assessors here:
➡ EPC Assessors London
➡ Book Your EPC Appointment
Email :info@epcrate.co.uk
Phone:020 34884142
