June 2023 marks the twelve-month anniversary of the update to the Building Regulations. But with the rise in FENSA assessment failures, there still appears to be confusion about where and how the new regulations apply. This is the view of Phil Parry, Business Development Director at Epwin Window Systems, who commented:

“The year-on-year increase in FENSA assessment failures is striking. In January to March 2023, 39% of FENSA assessments failed. In the same period last year, it was just 13%. What is more troubling is all 39% of this year’s failures were because they didn’t meet the evidence requirements of thermal efficiency of the new Part L of Building Regulations as well as other failures relating to Part F and Part C”.

Phil continued:“It’s fair to assume that following an update of Building Regulations, we’d naturally expect an uptick in the failure rate. However, the jump is unexpectedly large, given the extensive industry coverage.”

As documented, windows and doors on a new dwelling must meet a ‘notional’ U value of 1.2 W/(m2K) or a ‘limiting’ U value of 1.6 W/(m2K) for England and 1.4 W/m²K for Scotland and Wales. The ‘notional building specification’ is a recipe approach that ensures compliance if all standards are met. ‘Limiting U values’ are the worst acceptable level of performance, but designing to these values is unlikely to result in compliance.

Windows and doors installed in an existing dwelling need to meet a ‘limiting’ U value of 1.4 W/(m2K) (or a minimum Window Energy Rating of B/DSER Band C).

Phil said: “The first confusion is over the definition of ‘new dwelling’ and ‘existing dwelling’. A new dwelling covers everything from a large-scale property development to a new extension on an existing dwelling. The figures for an existing dwelling only apply when windows and doors are being replaced.”

He continued: “The second confusion is over how the U values are calculated. U values must be calculated as set out in the GGF’s Glazing Manual Data Sheet 2.3, which means the BS EN 14351 sample size of 1230w x 1480h must be an opening light next to a fixed light with a central divider, i.e., not a single opener”.

To help customers navigate the changes, Epwin Window Systems set out a series of Building Regulation downloads available from their Connect digital portal. And with over 1000 views, they have proven to be an essential source of reliable information.

Phil said: “As the UK’s largest manufacturer and supplier of PVC-U and aluminium window and door systems we have a responsibility to our customers to keep them informed and guide them, and their customers, through the changes. Our in-house technical experts can also provide additional insight or advice to ensure customers are complying at all levels.”

As we see from the data, these new regulations aren’t immediately straightforward and, in some instances, have been misinterpreted. With Epwin Window Systems, the clarity, guidance, and support are readily available to ensure fabricators comply.