Energy Performance Certificates
Your EPC may include useful information about your property's recorded wall construction and insulation — but an EPC is an energy assessment, not a specialist cavity wall condition inspection. This page explains what your EPC can and cannot tell you about your cavity wall insulation.
"Check My EPC" opens the official GOV.UK EPC Register in a new tab
Step by Step
Finding your EPC takes a few minutes and gives you a useful starting point for understanding your property's recorded wall construction.
Use the button on this page to open the official GOV.UK Find an Energy Certificate service in a new tab.
Open GOV.UK EPC RegisterEnter your postcode on the official EPC Register and select your property from the list of results.
Open the most recent Energy Performance Certificate for your property. Note the date — EPCs are valid for ten years.
Look for the section describing wall construction. It will typically appear in the energy efficiency features table or in the property details.
The wording describing your walls and insulation — particularly any terms such as "assumed" or "insulated" — is what this page will help you understand.
Understanding EPC Wording
"Cavity wall, as built, insulated (assumed)"
This is one of the most common descriptions a homeowner may see. Read below to understand what it does and does not mean.
EPC assessors record wall construction based on information available at the time of the assessment. Where cavity wall insulation appears to be present — typically identified from external drill-hole evidence, documentation, or local building records — the assessor may record the walls as "insulated".
The word "assumed" is important. It indicates that the insulation has not necessarily been physically verified by a specialist inspection of the cavity — it reflects an inference based on available information.
This does not mean the EPC assessor has done anything wrong. An EPC is an energy assessment, not a specialist CWI condition inspection, and assessors are not required to carry out invasive investigation of the wall cavity.
Common EPC wall descriptions
"Cavity wall, as built, no insulation (assumed)"
The cavity walls appear not to have insulation installed. This may be based on the absence of drill-hole evidence or documentation.
"Cavity wall, as built, insulated (assumed)"
The cavity walls appear to have insulation installed, based on available evidence. Not a specialist condition inspection.
"Cavity wall, filled cavity insulation"
Cavity wall insulation appears to have been installed. As above, this is typically based on observable evidence, not invasive inspection.
"Solid wall, as built, no insulation (assumed)"
The property appears to have solid wall construction rather than a cavity — typically properties built before the 1920s.
Understanding the Limits
An EPC is a valuable document — but it is important to understand what type of information it provides and what lies outside its scope.
This is not a criticism of EPC assessors. An EPC is an energy assessment and EPCs are not designed to be specialist cavity wall condition investigations. They serve different purposes and provide different types of information.
Comparison
Energy Assessment
Specialist Inspection
Signs to Look Out For
The following symptoms can sometimes be associated with cavity wall insulation problems — but they can equally arise from other causes. They do not automatically mean CWI is to blame or that extraction is required.
Damp staining or patches on internal walls, particularly on external-facing walls, may be worth investigating.
Mould growth, especially in corners or behind furniture, may indicate a moisture-related issue within the wall fabric.
External walls that feel noticeably cold even when the heating is running can be a sign that insulation is not performing as expected.
Condensation appearing consistently on walls — rather than just windows — can point to underlying moisture or thermal performance issues.
Peeling wallpaper, blistering paint or blown plaster on external walls may indicate moisture within the wall construction.
None of these symptoms automatically confirm a cavity wall insulation problem. Each property is different, and appropriate investigation is needed before any conclusion can be responsibly reached. Other causes — including penetrating damp, rising damp, roof defects, plumbing issues, or inadequate ventilation — should also be considered.
Property-Specific Approach
Where there are concerns about the condition of cavity wall insulation — whether prompted by an EPC, visible symptoms, or a property transaction — an OSCAR Onsite CWI Condition Inspection Survey provides a property-specific specialist assessment.
Our approach is always to inspect first, consider all available evidence, and provide clear and objective findings before any recommendations are made.
OSCAR's Approach
Inspect
Examine the property, cavity condition and all available evidence.
Investigate
Consider the insulation, external factors and any contributing defects.
Report
Provide clear and objective findings in a written report.
Recommend Next Steps
Advise on appropriate options based only on what the evidence supports.
What We Do
An accredited specialist inspection of your cavity wall insulation, with a detailed written report on its condition.
Find out moreWhere specialist assessment confirms extraction is needed, accredited OSCAR member firms carry out professional CWI removal.
Find out moreIndependent certification that cavities have been properly cleared — accepted by mortgage lenders, surveyors and solicitors.
Find out moreSpeak to our team about your property, a survey, accreditation, membership or any other enquiry.
Find out moreCommon Questions
Questions we are often asked by homeowners who have checked their EPC and want to understand what it means for their cavity wall insulation.
If you have checked your EPC and have concerns about the condition of your cavity wall insulation — or if you are seeing symptoms such as damp, mould or cold walls — a specialist CWI Condition Inspection Survey is the appropriate next step.