41906t
2 April 2025

SWA members wowing new markets with thermally broken Ottostumm profiles

Pictured is the Robert Hooke Science Centre at Westminster School which features Ottostumm's Ferro-Finestra W50 TB.

The evolution of steel windows within the UK is gaining fresh momentum as clients and consultants warm to the enhanced performance benefits of the new generation, thermally broken sections. These are made available through a partnership between theSteel Window Associationand a Swiss manufacturer that ensures the technology keeps faith with the appearance and heritage of our ubiquitous W20 windows, which distinguish so many of the UK's period properties.

Ottostummhas been supplying SWA members with its W20 and W40 steel profiles for decades but first introduced the W50 TB option into its range in 2016, where the two halves of the frame are separated by a specifically-shaped polyamide thermal break, which improves the insulation value and reduces the risk of condensation. 

The game-changer came in the form of Ottostumm's Ferro-Finestra W50 TB, cold rolled 3mm thick sections which still offered super slim sightlines and maximised glazing areas.  Factory-applied galvanising ensures an extended low maintenance life, while a wide selection of customised finishes is available. Opening vents can be top, side or bottom hung, horizontal and vertical pivots, while door options can include sliding and folding systems. There is a similarly broad choice in terms of glazing beads and modern as well as more traditional fittings.

London-basedWest Leighwas an early adopter amongst SWA members in the same year, followed, more recently, by sister company Cotswold Casements, though the latter manufacturer leans more to the domestic side of the market. West Leigh meanwhile has seen its total sales of W50 and W75 window packages top the £10 million mark, mainly based on large scale commercial contracts, mixed with a number of high end residential extensions, where owners were seeking the optimum in style, security and energy saving.  

Paul Cox, Commercial Manager for West Leigh, comments: "The Ottostumm W50 and W75 systems are increasingly popular among architects and owners of traditional, warehouse-style buildings because they replicate the classic aesthetics of the long-established W20 section while meeting modern Building Regulations. The W50 range accommodates glazing units up to 38mm thick, while the W75 can accept up to 52mm triple glazing, offering enhanced thermal and acoustic performance. Crucially, while other thermally broken steel window systems exist, they do not achieve the distinctive slim sightlines of the W20. The new W50 and W75 options can deliver U-values as low as 1.0 W/m²K, depending on the glazing specification and frame-to-glass ratio, with a standard reference window achieving around 1.4 W/m²K. These advancements ensure compliance with planning requirements in conservation areas and sensitive refurbishments. The future of steel windows is looking very bright."

The Steel Window Association is one of the UK construction industry's most respected trade bodies, committed to supporting its diverse membership through both technical and marketing support in their activities across the whole of the country, while also offering a knowledge resource for architects, planning bodies and other interested parties. Collectively, the SWA membership is able to undertake all types of projects, from new-build residential and commercial to the construction of high security premises such as prisons and secure mental institutions. Then for existing buildings, interventions can range from routine maintenance and repair up to replica replacement or full thermal upgrades, with retrofit weather-stripping and the fitting of new gas-filled and even vacuum sealed glazing units. 

For further information on the Steel Window Association or if you're interested in becoming a member, please visitwww.steel-window-association.co.uk

-ends-

With compliments:

Taylor Alden Ltd

Email:media@tayloralden.co.uk