A new Office for Product Safety and Standards report has uncovered systemic compliance failures across UK manufacturers of heat-soaked thermally toughened glass, with every insulated unit assessed failing checks. The findings carry significant implications for specifiers, fabricators, and building envelope consultants tracking documentation risk in their supply chains.
A Wake-Up Call for the Glass Supply Chain
A newly published regulatory report from the UK's Office for Product Safety and Standards (OPSS) has exposed widespread compliance failures across manufacturers of heat-soaked thermally toughened glass (HSTTG), raising urgent questions about documentation, traceability, and accountability throughout the global glazing supply chain.
The findings come in a sector regulatory report published on 5 March 2026 by the Office for Product Safety and Standards (OPSS), following an inspection programme targeting UK manufacturers of the safety-critical construction product. While the inspections were UK-based, the implications travel well beyond British borders for any architect, contractor, or facade consultant who specifies HSTTG in commercial, high-rise, or high-traffic environments.
What the Inspections Found
In total, OPSS inspected 28 UK manufacturers of heat soaked thermally toughened glass who conducted heat soaking using in-house equipment. The results were stark:
- Every single heat soaked insulated glass unit assessed failed compliance checks. Only half of the companies inspected were able to produce any form of Declaration of Performance at the point of inspection – a legal requirement on every manufacturing business.
- A further 93% failed to meet labelling requirements and 86% could not demonstrate compliance with marking requirements.
- Some manufacturers were unable to produce the legally required Declaration of Performance, while others could not demonstrate that their products had been tested against the relevant performance standards. In others there was no evidence of initial type testing or records to confirm that required factory production control tests had been carried out.
Importantly, the issue is not necessarily that the glass itself is unsafe. According to the Glass and Glazing Federation, what OPSS uncovered is not a systematic attempt to produce unsafe glass, but a systematic failure to maintain the evidence that proves products are safe and compliant. In too many cases the glass itself was fine, but the declarations, labelling and conformity marking were incomplete, out of date or simply non-existent.
Why This Matters for the Building Envelope
Heat-soaked thermally toughened glass is engineered to dramatically reduce the risk of spontaneous breakage caused by nickel sulphide inclusions in tempered glass. HSTTG is primarily used in construction applications where the product's performance and its safety are critical, such as settings with high footfall like commercial developments, high-rise buildings, infrastructure projects, and premium residential developments.
The scrutiny stems directly from post-Grenfell construction product reform. Established following the Grenfell Inquiry, OPSS has the power to stop the supply of products to the market where compliance cannot be demonstrated. That power has already been exercised, with several manufacturers prevented from selling HSTTG until they resolved documentation issues.
Potential issues in the HSTTG sector first came to OPSS' attention in a report by Collaborative Reporting for Safer Structures (CROSS-UK), published in November 2022, which identified challenges with HSTTG products including a significant issue with traceability, claims of absent or falsified factory records for the heat soaking process, and claims that glass marketed as heat soaked thermally toughened glass and compliant with BS EN 14179-2:2005 experienced far more nickel sulphide-related breakages than expected.
Practical Implications for Architects and Contractors
For specifiers and building envelope professionals, the OPSS findings translate into immediate due-diligence obligations:
- Verify Declarations of Performance at procurement. For building engineers and specifiers, the report reinforces the importance of verifying product documentation and quality assurance processes when selecting glazing systems, particularly where failure could pose a safety risk. Industry guidance has long emphasised that designers rely heavily on manufacturer records and certification to confirm that glass has been properly heat-soaked, as the process cannot be verified visually once the glass is installed.
- Audit supplier paperwork now. Businesses have allowed their conformity systems to decay—old managing director signatures on critical documents, outdated standards references, missing labels and missing declarations. All of those things are enough to trigger enforcement action. If something goes wrong on site and you do not have that documentation, you do not have a leg to stand on.
- Plan for supply disruption. OPSS prohibition notices can halt glass deliveries with immediate effect, putting facade schedules at risk if a supplier is caught short on technical files.
What Comes Next
The response is already underway. GGF Consulting is already working with IGU manufacturers, glass processors and fabricators, to audit documentation, rebuild technical files and ensure that Declarations of Performance and labelling systems remain current and compliant. In some cases that means starting from almost nothing. In others it means tightening up systems that were good in 2013 but have not kept pace with product changes.
PAS 2000:2026 has been published by BSI, providing a voluntary code of practice to help construction product manufacturers and other economic operators demonstrate that they have taken all reasonable steps to ensure their products are safe for their intended use.
The broader message for the global fenestration industry is unmistakable: as construction-product regulation tightens in the wake of Grenfell, paperwork is no longer an afterthought. For project teams specifying safety-critical glazing on high-rise and commercial work, demanding—and verifying—a complete documentary chain from float plant to installed unit is rapidly becoming a baseline standard of care.