Compliant by design

With the changes to Part L upon us, Paul Booth, design director at Epwin Window Systems and chair of the technical committee at the Council for Aluminium in Building [CAB], explains why its customers can be confident that the Stellar aluminium system will always be ahead of the curve.

On 15 June, one of the biggest shake-ups to Building Regulations in England for some time will come into force. When it comes to Part L, which covers the conservation of fuel and power, the changes are especially significant.

The changes are the first step towards the government’s Future Homes Standard, which says that by 2025, new homes will be zero-carbon ready. The changes being introduced this year will deliver a meaningful reduction in carbon emissions on the way to 2025.

What’s interesting about these new regulations is that, on the face of it, nothing too much has changed. Limiting U Values for existing dwellings and new dwellings are 1.4 W/(m²K) and 1.6 W/(m²K) respectively.

Look a little deeper, though, and you’ll see that everything has changed. Because the way window U values are calculated has become more demanding as part of these new regulations.

U values must now be calculated as per the GGF’s Glazing Manual Data Sheet 2.3, Guide to the Calculation of Energy Ratings for Windows, Roof Windows and Doors. U values can no longer be calculated on the CEN standard window.

The GGF’s calculation uses a window with an opening light next to a fixed light with a central mullion. The CEN standard window doesn’t have a mullion, which increases the glazed area and makes it easier to achieve a U value.

This change makes it much harder for windows that use workarounds in their construction to meet the new requirements. This is particularly true for aluminium systems, many of which use a dummy sash or rebate adaptor to create an internally beaded fixed light next to an opener. This results in more frame, which impacts the U value.

Our Stellar Aluminium System uses a patented reverse butt joint, which means there’s no need for dummy sashes, reverse profiles or adaptors so it’s more thermally efficient by design. Plus, its thermal break technology can be upgraded to meet the demands of thermal regulations that will only get stricter over time. It means we’re already ahead of the market.

To illustrate the difference the patented construction of Stellar makes, Epwin Window Systems calculated two GGF2.2 windows using their certified BFRC simulator. The first was a Stellar window constructed with a dummy sash. The second was a Stellar window constructed using the patented reverse butt joint. The results were conclusively in favour of the reverse butt jointed window which achieved a calculated improvement of 0.1W/m²K over the dummy sash variant.

As a result, Stellar meets the requirements of the new Part L legislation. It also has the added benefit of being all internally glazed and secure ready for the proposed amendments to Approved Document Q too. And for further optimal product performance, optional centre seals to the window outer frame and sash further improve insulation and weather protection delivering the best in aluminium product performance and giving our customers a strong commercial position.

From its initial concept, Stellar was designed by a talented team of in-house British aluminium specialists to be competitive yet future-proof. It was designed ready for the changes now and it’ll be ready in the future too.

Having secured numerous industry awards and accolades for the aluminum system’s capabilities, aesthetics and patented features, Stellar continues to gain market share across the industry. And with the introduction of the new Part L, there’s yet another reason for it to be the aluminium system of choice in fabricators’ and installers’ portfolios.