The W40 steel window system, available from members of the Steel Window Association (SWA), has been developed to meet the demands of both new-build and refurbishment projects. Combining the timeless appeal of steel windows with modern performance standards, W40 profiles deliver slim sightlines, exceptional strength and maximum natural daylight, making them a popular choice across commercial, residential and heritage applications.
Manufactured from hot rolled steel, W40 steel profiles offer greater design flexibility than traditional steel window systems. The profile can accommodate thicker double and triple glazing units, while enabling larger window and door openings without the need to couple multiple frames together. This provides architects and specifiers with greater freedom to create expansive glazed elevations without compromising aesthetics.
For doors, the W40 system delivers impressive thermal performance when combined with high-performance double or triple glazing. It also offers enhanced security, with multipoint locking systems available, while acoustic glazing options make W40 steel windows and doors ideal for busy urban environments where noise reduction is a priority.
The versatility of the W40 steel window profile is demonstrated at One America Street in London, where Steel Window Association member West Leigh supplied W40 frames as part of the major refurbishment of the headquarters of leading architectural practice TP Bennett. Situated close to The Shard and London Bridge Station, the project required a glazing solution that would preserve the character of the existing building while meeting modern standards for energy efficiency, comfort and weather performance.
At One America Street, W40 windows were specified to replicate the appearance of the original fenestration, while delivering substantial improvements in thermal efficiency, weather resistance and occupant comfort. On the building’s Keppel Row elevation, the W40 steel frames incorporated high-performance insulating glazing units featuring toughened and acoustic laminated glass, low-E coatings and Krypton gas-filled cavities. This specification enhanced both thermal and acoustic performance when compared with the original timber windows, helping create a comfortable working environment within a busy city-centre location.
The project highlights how W40 steel windows successfully combine authentic steel aesthetics with the energy efficiency, acoustic control and durability increasingly required for commercial refurbishment schemes and modern workplace developments.
The Steel Window Association represents specialist steel window manufacturers across the UK, ranging from heritage restoration experts working with conservation officers and listed buildings to large-scale fabricators supplying W40 steel window and door systems for offices, leisure facilities, apartment developments, schools, hospitals and public buildings.
A key advantage of the W40 profile system is its versatility. W40 can be used to create a wide range of opening configurations, including fixed windows, casements, screens and multi-leaf folding and stacking doors, all available in an extensive range of RAL colour finishes. With nationwide coverage, SWA members provide everything from steel window repair and restoration projects through to the design, manufacture and installation of large-scale W40 glazing packages for contemporary commercial, residential and public-sector developments.
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