Outstanding Energy Efficiency
These windows are fully compliant with Approved Document L, ensuring exceptional energy efficiency while keeping your space comfortable year-round.
The Corporate W20 is Crittall’s flagship rolled-steel window system, instantly recognisable for the ultra-slim sightlines and crisp shadow lines that have defined steel-framed architecture for more than a century. Manufactured from hot-rolled steel sections and finished to your exact specification, genuine W20 windows deliver an authenticity that aluminium and uPVC “Crittall-style” lookalikes simply cannot replicate.
As an established Crittall specialist partner since 1935, Lightfoot does far more than supply W20. We survey, advise, manufacture to measure, install and support your project from the first enquiry through to aftercare, with showrooms serving London and Milton Keynes and completed projects nationwide. Whether you are restoring period steel windows or specifying a striking new installation, our team makes sure every detail is right.
Genuine rolled-steel windows engineered for authenticity, strength and design freedom: backed by Lightfoot’s full supply-and-install service.
These windows are fully compliant with Approved Document L, ensuring exceptional energy efficiency while keeping your space comfortable year-round.
The innovative co-extruded dual weather seals provide unbeatable weather performance, protecting your property from the elements while maintaining a comfortable indoor environment.
Available in various finishes, including classic black steel, Crittall W20 TE windows can be tailored to complement the existing design of your property, whether it's a modern residential project or an industrial design scheme.
The Corporate W20 is the original Crittall steel window, formed from hot-rolled steel sections rather than the aluminium or uPVC used in “Crittall-style” alternatives. Its defining characteristic is the slim sightline: the narrow frame depth that lets in more light and creates the crisp, gridded look associated with classic steel glazing. Because the sections are genuinely steel, W20 windows are exceptionally strong, allowing large panes and slender bars that would be impossible in weaker materials. This combination of strength and slimness is exactly why architects and homeowners specify W20 for everything from listed-building restorations to contemporary glass-led extensions.
Choosing between the two Crittall systems comes down to your priorities. The standard W20 is the most authentic option, with the slimmest possible frames: the natural choice when you are matching existing steel windows in a period or listed property and want to preserve the original character. The W20 TE, or Thermally Enhanced, introduces a thermal break within the frame to dramatically reduce heat transfer, achieving the lower U-values demanded by modern Building Regulations on new builds and major renovations. If energy efficiency and compliance are your main concern, W20 TE is usually the right answer; if authenticity and the slimmest sightlines come first, the classic W20 wins. Our team will assess your property, planning constraints and performance goals and recommend the best fit.
A common question about steel windows is how they perform thermally. Traditional single-glazed steel frames conduct heat readily, which is why modern specifications often call for double glazing and, where performance is critical, a thermally broken frame. The W20 can be double glazed for improved comfort, while the thermally enhanced W20 TE incorporates a thermal break that interrupts the path of heat through the frame: the key to meeting today’s energy standards without sacrificing the steel-window aesthetic. For homeowners weighing up restoration versus replacement, modern thermally broken steel systems offer the look of original windows with vastly improved efficiency.
Every W20 window is bespoke. Frames can be finished in any RAL or BS colour, with black steel and the grey family being the most requested, all protected by a galvanised and polyester powder-coated finish. Glazing can be specified as single or double to suit the project and performance requirements. To complete the installation, choose from a full range of period and contemporary hardware: including the industrial Soho and minimalist Phoenix casement handles, plus traditional peg stays and sliding stays: so the finished window is coordinated down to the last detail.
See how authentic Crittall W20 steel windows transform period properties, new builds and commercial spaces. Browse a selection of our completed installations across London, the South East and beyond: then picture the possibilities for your own project.
Colours
Crittall W20 TE windows are available in a variety of finishes, including iconic black steel, allowing for a cohesive look that enhances the contemporary feel of your space. With options for bespoke shades, you can achieve the perfect aesthetic for any project.
Hardware
Our windows come with flexible installation options, paired with durable hardware that meets the highest quality standards. This ensures that your Crittall W20 TE windows not only look stunning but also function flawlessly for everyday use.
Downloads
Access our downloads section below to find detailed specifications and design resources for our W20 TE windows, engineered to deliver superior thermal efficiency without compromising on style.
Everything you need to know about the Corporate W20 steel window system: from how it differs from the thermally enhanced W20 TE, to colours, glazing and cost. Still have a question? Speak to a Lightfoot specialist
The Corporate W20 is Crittall’s original rolled-steel window system, known for its slim sightlines and durable hot-rolled steel frames. It is the authentic steel window specified for both period restorations and contemporary architecture, offering a finely detailed frame that modern lookalike products cannot match.
The W20 is the original, non-thermally-broken system: ideal for authentic, like-for-like heritage replacement. The W20 TE (Thermally Enhanced) adds a thermal break within the frame to significantly improve insulation and energy performance, making it the better choice for new builds and full renovations where U-values matter. Our team will help you choose the right system for your project.
W20 windows are made to measure, so the price depends on the size, configuration, glazing and finish of your project, as well as whether you need installation or supply only. The most accurate way to find out is to request a free, no-obligation estimate from our team.
Yes. The W20 system can be specified with double glazing for improved comfort and efficiency over single glazing. If thermal performance is a priority: for example to meet Building Regulations on a renovation: ask us about the thermally enhanced W20 TE system, which is designed to achieve lower U-values.
W20 windows can be finished in any RAL or BS colour. The iconic black steel finish remains the most popular, alongside the grey family: Anthracite, Agate and Light Grey: and white. Frames are galvanised and polyester powder coated for a durable, low-maintenance finish that lasts.
Both. Lightfoot offers a complete survey-and-install service as well as supply-only options for trade and self-managed projects. As a Crittall specialist partner since 1935, and we will recommend the right approach and support you throughout, from showroom consultation to final installation and aftercare.