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The new W30 style meets the latest Building Regulation requirements for domestic dwellings while looking every bit the definitive example of a traditional steel window.

Until now the problem that the industry faced was how to improve thermal performance without radically changing the design of the window and the W30 has been created so that Steel Window Association members can now deliver a Part L compliant product for both the replacement market and domestic new build.

The W30 is BFRC registered and achieves a Window Energy Rating (WER) Level C. In fact, it’s the only steel window to achieve this rating.

A spokesperson for the SWA explains that the industry worked long hours to make the British Fenestration Rating Council simulator give the results needed: “We were looking for a way to comply with the latest regulations, using the maximum amount of W20 and SMW sections. This was to preserve the classic lines of the steel window ensuring that the new W30 profile could convincingly replace traditional window types, meet the thermal properties and reduce costs.”

The new design incorporates sections from the classic windows used in different ways. As a result larger sealed units can be incorporated and a ‘C’ energy efficiency rating is achieved.

The critical problem was to reduce the amount of material facing the elements and the SWA members design team also specified warm edge spacers, low iron (to boost solar gain), soft coat low-e glass and Krypton gas. Particular trouble was taken to ensure that exactly the right double glazing unit gap was established in order to make the Krypton as effective as possible. It turned out that a 10mm space between the two panes works best.

The W30 profile is designed to fit neatly into the slot left by the huge bulk of existing steel windows since it has almost identical sight lines to the widely used SMW F-range profiles. Like SMW, W30 offers top and side-hinged casements, plus fixed lights, in both single and multi-light configurations. Such classic appearance on a high performance 21st century steel window will also be of interest to architects and others involved in building high specification new homes.

"I think everyone is pleased that W30 can achieve a ‘C’ rating," said the SWA spokesperson. “It means they can meet all the statutory requirements while maintaining the unique slim frame looks of steel windows.”