Let’s be honest: if you’re involved in large-scale domestic retrofit, the phrase “TrustMark Audit” probably makes your heart rate spike just a little bit. We’ve all been there. With the rollout of the Warm Homes Plan 2026 and the pressure to hit EPC C by 2030 for landlords, the stakes for PAS 2035 compliance have never been higher.

At CPH Retrofit, we’ve spent over 15 years on the front lines as installers and energy efficiency consultants. We’ve seen the good, the bad, and the “how on earth did they think that would pass?” Whether you are managing a social housing decarbonisation fund (SHDF) project or a private landlord portfolio, the Retrofit Coordinator is the glue that holds the whole project together. But often, that glue is a bit… thin.

If you want to survive the next audit from the Warm Homes Agency or your accreditation body, you need to stop making these seven common mistakes. Here’s how we fix them using real-world, hands-on experience.

1. Treating the Retrofit Assessment as a "Tick-Box" Exercise

One of the most frequent errors we see is rushing the Retrofit Assessment. Some coordinators treat the assessment like a standard EPC: a quick 20-minute walk-through.

The Mistake: Using incomplete or inaccurate data to speed up the project. If your assessment doesn't include a detailed condition survey or fails to identify structural issues like rising damp or crumbling masonry, your entire design is built on sand.

The Fix: You need to ensure your assessors are looking at the entire building. Under PAS 2035:2023, the assessment must be comprehensive. At CPH, we recommend a "measure twice, cut once" philosophy. Before the audit, review your assessment files. If there isn't a clear record of the building's current condition, occupancy, and energy use, you’re looking at a major non-conformance.

2. Ignoring the "Fabric-First" Hierarchy

We get it: renewable tech is exciting. Heat pumps and solar PV look great on a sustainability report. But if you’re specifying a high-tech heating system before you’ve addressed a drafty, uninsulated building envelope, you’re failing PAS 2035.

The Mistake: Prioritizing technology over the building fabric. This isn't just bad practice; it’s a violation of the fundamental principles of domestic retrofit.

The Fix: Always follow the hierarchy: Insulation → Airtightness/Ventilation → Heating/Renewables. Your Retrofit Coordination logs must demonstrate that you considered fabric improvements first. If you skipped them, you need a documented, technical reason why (e.g., the building was already at peak thermal performance).

3. The "Communication Silo" Trap

In many projects, the Assessor, the Designer, and the Installer barely speak to each other. They operate in silos, and the Coordinator only steps in to sign off the paperwork at the end.

The Mistake: Acting as a "paper-pusher" rather than a project hub. When roles are disconnected, you end up with designs that are impossible to install or ventilation strategies that don't match the new airtightness of the building.

The Fix: You need to be the central point of truth. Hold regular "toolbox talks" between the design and installation teams. Ensure the installer understands the designer’s intent. We’ve found that TrustMark registered businesses that foster open communication have a 40% lower remediation rate.

4. Documentation Gaps (The Audit Killer)

If it isn't documented, it didn't happen. That is the golden rule of TrustMark compliance.

The Mistake: Missing photographic evidence, unsigned declarations, or lack of "As-Built" records. Audits often fail not because the work was bad, but because the proof was missing.

The Fix: Implement a digital-first documentation strategy. Every stage of the installation should be captured in real-time. This includes photos of insulation thickness, floor-to-wall junctions, and ventilation ducting before they are covered up. If you're scrambling for photos the day before an audit, you've already lost.

5. Forgetting the Human Element (Occupant Lifestyle)

A house isn't just a thermal envelope; it’s a home. We’ve seen perfectly designed retrofits fail because the coordinator didn't account for how the residents actually live.

The Mistake: Ignoring occupancy assessments. If a resident dries laundry on radiators or keeps windows permanently locked, your "perfect" ventilation strategy might lead to condensation and mould.

The Fix: PAS 2035:2023 places a huge emphasis on occupant engagement. You must document that you’ve assessed the residents' needs and, more importantly, that you’ve explained the new measures to them. Provide clear, simple handover packs. This isn't just a "nice to have": it’s a compliance requirement.

6. Using Non-Accredited Installers

With the surge in demand driven by the Warm Homes Plan, there are a lot of new players in the market. However, not all of them have the pedigree required for PAS 2030 compliance.

The Mistake: Failing to verify the PAS 2030:2023 accreditation for specific measures. Just because a company is "TrustMark Registered" doesn't mean they are certified for every measure (e.g., they might be certified for loft insulation but not for Internal Wall Insulation).

The Fix: Do your due diligence early. Check the Stroma Certification or other body databases. At CPH Retrofit, our 15 years of installer experience means we know exactly what to look for in a sub-contractor’s credentials. We highly recommend implementing C3 Technical Monitoring to catch installer errors before they become permanent fixtures.

7. Staying Stuck in 2019 (The Update Oversight)

The industry moves fast. If you are still coordinating projects based on the 2019 version of PAS 2035, you are essentially working with an outdated map.

The Mistake: Not aligning with the PAS 2035:2023 updates. The new standards brought in clearer definitions of roles, more rigorous risk assessments, and a heavier focus on "Retrofit Remediation" for failed projects.

The Fix: Schedule a mandatory team update. Review your internal processes against the 2023 standards. Are your risk assessments still relevant? Are your ventilation calculations following the new annexes? If you're unsure, it’s time to consult with an expert.

Why "Good Enough" Isn't Good Enough Anymore

The landscape of UK energy efficiency is changing. With the Warm Homes Agency taking a more active role in oversight, the days of "flying under the radar" are over. Whether you are aiming for non-domestic energy performance certificates or residential compliance, the quality of your coordination determines the longevity of your business.

At CPH Retrofit, we offer more than just consulting; we offer peace of mind. Our team has lived and breathed retrofit for over a decade and a half. We know the pitfalls because we’ve had to climb out of them ourselves in the early days of the industry.

Need an Audit-Ready Review?

Look no further! If you're worried about your current PAS 2035 projects or need a hand navigating the complexities of the Warm Homes Plan 2026, we are here to help. From air pressure testing to full-scale project coordination, we provide a one-stop shop for retrofit excellence.

Don't wait for the audit notification to drop in your inbox. Fix these seven mistakes today and ensure your projects contribute to a greener, warmer, and more energy-efficient UK.

Ready to streamline your compliance? Contact our expert team at CPH Retrofit today.