Answer extracted from the Glazing Insider podcast — listen to the full episode below.
What makes the PLC scheme different from other window certification databases?
The PLC scheme (Part L Compliance) was set up last year to provide detailed, transparent approvals for window and door specifications—showing exactly which frame types, glass configurations, and performance details are approved on a searchable public database. Other certification schemes only confirm that a company can make an A-rated window without publishing the specifics, making the PLC approach fundamentally more useful and verifiable for specifiers and manufacturers.
Unlike traditional certification databases that keep approval details opaque or generic, the PLC scheme publishes granular specification information online with filterable search. This means you can search for the exact frame profile, glass type, seal configuration, and thermal U-value combination you need—and immediately see if it's already been approved and by which testing body.
As John Warburton explains in the episode, the transparency has become the industry standard for Part L compliance verification. The scheme now has approximately 80 approval companies participating, with one major manufacturer holding over 2,500 individual approvals on the platform.
"I think we provide a very, very good service. Customers seem to appreciate what we do. I think we're firm but fair."
John Warburton — Managing Director of ER Certification Ltd. Warburton has spent over 40 years in the fenestration industry, starting in the mid-1980s at a small PVC window fabricator in Lancashire where he learned manufacturing from the ground up. He progressed through roles including field technician at Profile 22, exports manager during the global recession, technical manager at Commolin, and product development roles at Vika and Epwin. He later joined the Building Research Establishment (BRE) in Watford to help set up government certification schemes for windows and doors, before purchasing and leading ER Certification.
The searchability built into the PLC scheme solves a real problem in the industry: specifiers and fabricators no longer have to guess whether their chosen configuration exists in any database. They can filter by frame material, glass specification, sealing system, and performance rating in seconds. This level of transparency reduces design rework and accelerates certification timelines for new products.
Prior schemes relied on companies claiming compliance without public proof of what they'd actually tested. The PLC model inverts this: approvals are published with full technical detail so anyone in the supply chain can verify instantly. This is why the conversation in Glazing Insider emphasizes the PLC scheme as a major step forward in industry accountability.
For more context on certification challenges in the fenestration sector, discover John Warburton's full conversation on testing failure rates and how modern regulations have transformed product quality across the industry.
See also
Why are trickle vents problematic in modern thermally efficient windows?
Trickle vents destroy the thermal performance of highly efficient windows by putting holes through them. A government study published in 2019 found that they significantly compromise the insulation properties modern standards are designed to achieve.
What is the typical failure rate for windows and doors during certification testing?
The failure rate is around 70% per visit when testing windows and doors across all factors. Products rarely get through everything without a single issue on their first attempt.
What is the biggest change in the fenestration industry over the past 40 years?
The biggest change has been driven by standards and regulations pushing product quality much higher. Products from the 1980s were basic and insecure, but modern regulations have transformed the industry's commitment to performance and safety.