Cavity wall insulation (CWI) has long been marketed as a surefire way to improve a property’s energy efficiency. However, if your insulation was installed decades ago—or with outdated techniques—your Energy Performance Certificate (EPC) rating could be silently suffering.
At EPCrate, we often encounter properties where aged or compromised cavity wall insulation is dragging down EPC scores, even when owners assume the insulation is helping.
How EPC Assessments Account for Cavity Wall Insulation
During an EPC survey, assessors determine:
Whether cavity walls are insulated.
The method and quality of insulation (full-fill, partial-fill, blown-in, etc.).
The age and integrity of the insulation—especially if records are vague or installation predates modern standards.
EPC software generally applies efficiency credits for cavity insulation, but older methods and signs of insulation failure can lead to downgrades or default assumptions that reduce the EPC benefit.
Common Outdated Cavity Wall Insulation Methods That Harm EPC Ratings
1. Early Blown Mineral Wool (Pre-1980s)
Older mineral wool installations are prone to slumping, leaving uninsulated voids over time. Moisture retention and thermal bridging become serious concerns.
2. Polystyrene Bead Installations Without Bonding Adhesives
Early cavity bead systems sometimes lacked proper bonding agents, leading to bead settlement, voiding, and poor air sealing.
3. Urea-Formaldehyde Foam Insulation (1970s-1980s)
Once popular for its ease of injection, urea-formaldehyde foam has been known to shrink, degrade, and release harmful gases over time. EPC assessors are trained to spot and downgrade this insulation type.
4. DIY or Uncertified CWI Installations
If cavity wall insulation was installed without certified paperwork (CIGA Guarantee or equivalent), assessors may default to a conservative assumption, penalising EPC efficiency credits.
How Outdated Cavity Wall Insulation Can Lower Your EPC Score
Thermal Bridging & Voids: Insulation gaps result in cold bridging, which EPC software interprets as increased heat loss.
Increased Air Infiltration: Poorly installed insulation can worsen draughts, affecting EPC air permeability calculations.
Moisture Issues: Deteriorated insulation that allows water ingress leads to downgraded wall U-values in EPC assessments.
Lack of Documentation: Without proof of specification and installation quality, default values (often worse than uninsulated assumptions) may apply.
Signs Your Cavity Wall Insulation May Be Hurting Your EPC
The insulation was installed before 1990.
You experience cold patches on internal walls.
There’s evidence of damp or condensation near cavity walls.
You lack installation paperwork or guarantees.
Your current EPC has a lower-than-expected wall efficiency rating, despite declared insulation.
Solutions: How to Rectify EPC Issues Caused by Old Cavity Insulation
Thermal Imaging Surveys
Conduct a thermal imaging inspection to identify cold spots, insulation voids, and moisture ingress.Cavity Wall Insulation Extraction & Re-Installation
If the insulation is failing, specialist contractors can extract old material and re-install modern, certified insulation.Provide Updated Documentation
After remedial work, ensure certificates and U-value calculations are documented for future EPC assessments.Air Tightness Improvements
Complement wall insulation upgrades with draught-proofing and air permeability tests to enhance EPC results.Full SAP Assessment for Complex Cases
If RdSAP defaults continue to penalise, consider a bespoke SAP assessment for a more precise thermal performance evaluation.
Book a Cavity Wall Insulation-Aware EPC Assessment with EPCrate
Concerned that old cavity wall insulation is harming your EPC rating?
EPCrate’s expert assessors can advise on documentation, inspections, and upgrading strategies to ensure your property’s true efficiency is reflected.
Book your EPC assessment today or explore our pricing plans.
