Improving thermal efficiency without sacrificing design 

• 14 August 2025
• News

If asked why steel is chosen ahead of uPVC or aluminium for a window frame, most buyers would plump for looks. And why wouldn’t they? Steel windows have a unique and unmistakable elegance, coupled with narrow frames that help to catch the light and open up a space. But behind the beauty lies a question every architect, developer and homeowner must face. Can you keep that iconic style and still meet today’s demanding energy standards? 

The answer is yes. And Crittall’s W20 TE system proves it. 

This latest generation of thermally efficient steel windows combines classic visual appeal with high-performance engineering. At a time when we are all are looking to reduce energy use without compromising design, W20 TE offers a solution that is both intelligent and beautiful. 

A more efficient future for steel

The W20 TE system has been developed to significantly improve thermal performance through the integration of technology that uses a clever adaption of the profile to achieve the performance of a thermally broken product. This involves an innovative modification to the standard rolled steel profile to reduce thermal transfer, cutting down on heat loss and helping to maintain a stable indoor temperature all year round. 

Working in conjunction with high-performance glazing, the system improves insulation and limits condensation, supporting comfort, health and energy efficiency across all seasons. For those seeking to lower energy bills and reduce their environmental footprint, these innovations offer real value. 

Yet while the technology is advanced, the appearance remains unmistakably Crittall. The slim steel frames, large panes of glass and distinctive sightlines all stay true to the material’s heritage, making this a system that respects the past while embracing the future. 

Durability, longevity and minimal maintenance

The enduring appeal of steel lies in both looks and performance over time. W20 TE windows and doors are manufactured from solid, 100 percent recycled steel and are designed to last well beyond 60 years with minimal maintenance. Galvanised and powder-coated for long-term protection against corrosion, the system stands up to the most demanding environments, from coastal exposure to urban pollution. 

Compared with aluminium or timber alternatives, steel offers superior structural strength and resistance to movement or degradation. For homeowners and building professionals alike, this translates into reliability, stability and lower lifecycle costs. 

A versatile solution for every setting

From period renovations to contemporary new builds, the W20 TE range offers exceptional versatility. Casement windows, internal screens, door systems and curtain wall applications can all be achieved with the same refined detail and outstanding performance. 

Available in RAL, BS or bespoke colour, the frames can be tailored to suit any design scheme. Whether restoring a traditional home or creating a bold architectural statement, the system brings clarity and cohesion to the design, allowing natural light to define the interior. 

More than form. More than function.

The W20 TE range is about more than meeting regulations or reducing energy consumption. It is about building spaces that last, combining steel’s inherent strength with modern thermal efficiency and ensuring that the beauty of great design is never lost in the pursuit of performance. 

To explore how Crittall’s thermally efficient steel windows can support your next project, contact our team.