How Installers Stay PAS-Compliant and Avoid Failures
External Wall Insulation (EWI) is one of the best retrofit measures for cutting heat loss and improving EPC ratings. But under PAS 2030/2035, the margin for error is razor-thin.
Mistakes don’t just mean expensive remedials—they can cost installers funding, damage reputations, and even compromise occupant safety.
Why Getting External Wall Insulation Right Matters
External Wall Insulation (EWI) is one of the most closely monitored measures within the ECO and GBIS frameworks. This heightened scrutiny stems from a history of EWI failures over recent years, which has prompted stricter compliance and auditing standards.
Find and Fix
Under TrustMark’s “Find and Fix” initiative, Retrofit Coordinators (RCs) now face significant financial implications if non-conformities are identified during audits. A fee of £395 + VAT is charged to the RC when an issue is found on a project that includes Internal Wall Insulation (IWI)—even if the non-conformity does not relate directly to the EWI installation. Additionally, TrustMark may apply a discretionary £50 review fee once remedial evidence has been submitted.
Are there costs to the Installer?
Yes, In practice, these costs are often passed on to installers by the RC. This makes it absolutely critical for both parties to ensure that installations and documentation meet all compliance requirements from the outset. Attention to detail and robust quality assurance processes are no longer optional—they are essential to avoid costly penalties and maintain trust in the retrofit process.
Here’s a no-nonsense guide to the 7 biggest compliance risks in EWI—and how to avoid them.
1. Substrate Preparation — The Hidden Foundation
Biggest Fails:
- Leaving dirt, algae, or loose render in place.
- Ignoring cracks and damp ingress.
- Skipping adhesion pull-off tests.
Stay PAS-Compliant:
✔ Repair cracks and damp before install
✔ Clean thoroughly and check substrate soundness
✔ Test adhesion and keep photo records
2. Fixings & Adhesives — Secure, Don’t Guess
External Wall Insulation Biggest Fails:
- Using the wrong anchor for the substrate
- Poor embedment depth leading to board movement
- Skipping wind-load pull-out tests
Stay PAS-Compliant:
✔ Follow the fixing design for each elevation
✔ Record pull-out test results
✔ Never “eyeball” fixing patterns
3. Junctions, Edges & Openings — The Weakest Links
Biggest Fails:
- Poor detailing at sills, verges, and rooflines
- Missing trims and closures
- Gappy overlaps at DPC levels
Stay PAS-Compliant:
✔ Seal window reveals, roof eaves, and verges
✔ Fit trims as per system spec
✔ Document all junction closures with photos
4. Fire Stops & Compartmentation — Non-Negotiable
Biggest Fails:
- Omitting fire breaks altogether
- Installing them too high/low across floor slabs
- Using the wrong material instead of mineral wool
Stay PAS-Compliant:
✔ Check every elevation against fire design
✔ Photograph fire stops before covering
✔ Use only approved materials
5. Weatherproofing External Wall Insulation — Keep the System Dry
Biggest Fails:
- Rendering in wet, frosty, or blazing hot conditions
- Poor sealing around pipes and vents
- Rushing curing times
Stay PAS-Compliant:
✔ Render in safe weather windows only
✔ Seal penetrations with system-approved collars
✔ Use temporary protection when weather turns
6. Ventilation & Moisture Management
Biggest Fails:
- Blocking airbricks and trickle vents
- Ignoring ventilation upgrades when airtightness increases
Stay PAS-Compliant:
✔ Extend all airbricks through the system
✔ Maintain trickle vents
✔ Coordinate with the retrofit coordinator on MVHR or PIV upgrades
7. Documentation & Handover — Proof is Everything
Biggest Fails:
- Missing evidence for fixings, fire stops, or junctions
- No homeowner handover pack
- Incomplete installer declarations
Stay PAS-Compliant:
✔ Photograph every stage (“if it’s not pictured, it didn’t happen”)
✔ Provide digital handover packs with care & maintenance info
✔ Keep installer declarations complete and signed
Quick PAS Checklist for Installers
- Substrate tested, repaired, and sound
- Correct fixings & adhesives installed and logged
- Junctions sealed and trims fitted
- Fire barriers installed and photographed
- Weather protection applied correctly
- Ventilation preserved or upgraded
- Documentation and handover complete
Final Word
EWI delivers massive benefits—but under PAS, detail is everything. Most failures aren’t about the insulation itself; they come from prep, junctions, weatherproofing, and poor record-keeping.
Get those right, and you’ll:
- Pass audits first time
- Protect ECO and funding streams
- Future-proof your installs
- Build long-term trust with clients
External Wall Insulation is highly scrutinised and audited within the ECO and GBIS environment. Get it wrong at your peril…
