Energy Performance Certificates (EPCs) are essential for property compliance, sales, and rentals. Yet, many homeowners and landlords are shocked when a property fails to achieve the expected rating. Often, the issues are hidden, rare, or overlooked during regular maintenance. Understanding these can help you avoid surprises, improve energy efficiency, and ensure compliance.

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1. Hidden Thermal Bridges

Even modern homes with insulation can have areas where heat escapes due to thermal bridging.
Common locations include:

  • Corners of walls and roof junctions

  • Steel or concrete structural beams

  • Balcony connections

  • Floor-to-wall junctions

These bridges allow heat to bypass insulation, lowering EPC scores unexpectedly.

Our EPC Assessors London identify these hidden problems accurately.

2. Unnoticed Draughts and Air Leaks

Small gaps in doors, windows, or loft hatches can dramatically reduce efficiency. Many homeowners assume their modern double glazing prevents heat loss, but tiny leaks often go unnoticed:

  • Poorly sealed window frames

  • Gaps around loft hatches

  • Vents without backdraft shutters

Sealing these can quickly raise your EPC rating.

3. Outdated or Inefficient Heating Controls

Even with a modern boiler, your EPC can fail if heating controls are inadequate:

  • Old or missing thermostatic radiator valves (TRVs)

  • Inefficient programmable thermostats

  • Unbalanced heating systems

Upgrading these controls is a cost-effective EPC improvement.

4. Incorrect Documentation or Building Data

Sometimes an EPC fails due to errors or missing information:

  • Renovations not reported

  • Incorrect floor plans or room dimensions

  • Outdated building specifications

Professional assessors check documentation thoroughly to prevent these mistakes.

5. Recessed Lighting or Fixtures Breaking Insulation Continuity

Modern lighting and built-in cabinets can unintentionally reduce energy performance:

  • Downlights cutting through loft insulation

  • Gaps behind built-in furniture

  • Uninsulated pipework in concealed areas

These rarely visible issues are often flagged during EPC inspections.

6. Poor Ventilation System Performance

Mechanical ventilation systems (MVHR or extractor fans) may leak heat if:

  • Ducting is uninsulated

  • Dampers/backdraft shutters fail

  • System balance is incorrect

Even small ventilation inefficiencies can negatively impact EPC ratings.

Why Professional EPC Assessment Matters

A certified Domestic Energy Assessor (DEA) can detect these uncommon problems and advise on remedial action.

  • Accurate rating based on actual building performance

  • Identifies hidden issues affecting efficiency

  • Provides actionable recommendations to improve EPC

Learn more or get in touch via our Contact Page.

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Avoid unexpected EPC failures. Schedule your assessment with our qualified London EPC assessors for accurate, actionable results.

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