What has been announced
Speaking at the Glazing Summit on 8 October 2026, OPSS confirmed it had already bought gas-testing equipment and planned spot checks on the factories that make sealed units, the glass-and-spacer sandwich at the heart of every double glazed window. Fabrication & Glazing Eye names the speaker as Richard Poate, an OPSS enforcement officer. We could not find a published OPSS statement on the checks, so what follows comes from the trade press and the GGF.
Kevin Jones, the GGF's technical director, put it plainly:
The OPSS has confirmed that it will be visiting IGU manufacturers and checking the gas content of units coming off production lines.
Kevin Jones, Technical Director, Glass and Glazing Federation, via Fabrication & Glazing Eye, 14 October 2026
OPSS has been the national regulator for construction products since April 2021, a role that followed Dame Judith Hackitt's 2018 review of building regulations and fire safety. Glass is one of its targets already. In March 2026 it published its first sector report, on heat soaked toughened glass, and said it plans similar work in other product sectors. Sealed units now look like the next one.
Why the gas matters to you
Argon is the standard fill for double glazing because it slows heat across the cavity better than air, and the U-value printed on your quote is calculated on the assumption that the gas is there. Our comparison of argon and krypton covers how much each gas is worth. If a unit leaves the factory with less argon than declared, the window is worse than its paperwork from day one, and you would never see it: an under-filled unit looks exactly like a full one.
| Figure | What it means |
|---|---|
| 90% argon | Typical nominal fill, per the GGF |
| 5 points | Largest shortfall BS EN 1279-3:2018 allows against the nominal figure |
| 85% argon | The floor for a unit declared at 90% |
| BS EN 1279-5:2018 | The designated product standard for sealed units in Great Britain |
| BS EN 1279-6:2018 | Factory production control and periodic testing |
Gas also leaves slowly over a unit's life, and a well-made unit should lose only a small share of it over decades. When a seal fails outright, the argon goes and condensation appears between the panes, which our guide to blown double glazing covers. The new checks are about something different: whether the gas was there to begin with.
What the regulator did last time
OPSS's toughened glass programme is the best guide to how it works. Its March 2026 report covered all 28 UK manufacturers that heat soak toughened glass in-house. Every one failed to provide a compliant Declaration of Performance at the first inspection, and only half could produce one at all. It issued nine Prohibition Notices to six manufacturers, stopping them supplying until they fixed the problems, and warnings to 25 of the 28. OPSS added that the low compliance it found "may point to systemic non-compliance throughout the wider UK glass industry".
The GGF's reading at the time was that the glass itself was often fine and the paperwork was not. The same risk applies here. The trade press expects serious failures to bring prohibition and minor ones improvement notices and re-testing, but OPSS has not said so for sealed units, and the GGF says it is still seeking answers on sampling, what counts as a failure and the enforcement that follows.
Will it change prices?
Not on any evidence yet. One trade title has asked whether prohibitions could cause a shortage of units, but that is a question, not a forecast, and OPSS has not started publishing results. A firm that already tests and records its gas fill should see no change. If a quote rises and the reason given is "the new gas rules", ask what exactly changed for that supplier. Our cost by glass spec guide shows what an A-rated argon unit normally adds, and the quote quality auditor checks a quote for the details that should be on it.
This is good news for buyers, and it is not a reason to worry about windows you already have. The gas fill has always been a number you took on trust. Now someone with powers is going to check it. Ask for the declared figures in writing and you have done your part.
Double Glazing Cost Calculator Team
What to do next
If you are pricing new windows, the gas fill is one line on a spec, not a reason to delay. Get a range from the uPVC window cost calculator, read our plain-English guide to U-values so the figures on a quote make sense, and compare quotes from local installers with the four questions above in hand.
Frequently asked questions
The gas content of sealed double glazing units as they come off UK production lines. OPSS told the Glazing Summit on 8 October 2026 that it had already bought testing equipment and plans spot checks on sealed unit manufacturers. The Glass and Glazing Federation expects the visits to look at factory records and Declarations of Performance as well.
The GGF's technical director says most manufacturers fill to 90% argon. Under BS EN 1279-3:2018 the concentration can fall at most five percentage points below the nominal figure used to calculate the declared U-value, so a unit declared at 90% should hold at least 85%.
Nobody has said so. No test results have been published, and the GGF is still asking OPSS how it will sample and what will count as a failure. What the checks do is put a regulator behind the number your U-value is calculated from, which until now has rested on the manufacturer's own records.
Not with anything you own. What you can check is the paperwork: ask your installer who makes the sealed units, what gas fill and U-value they are declared at, and for the Window Energy Rating of the whole window, which is calculated from the same figures.
Same regulator, same approach. In March 2026 OPSS reported on 28 manufacturers of heat soaked toughened glass: every one failed to provide a compliant Declaration of Performance at first inspection, and six received a total of nine Prohibition Notices. OPSS said then that it plans similar work in other product sectors.