How Crittall W20 TE achieves U-values 1.4 w/m²k: engineering explained

• 3 April 2025
• News

Achieving the balance between preserving classic design and meeting modern performance standards is essential in today’s architectural landscape. Although it may seem like a challenging task to find window systems of the highest quality, that offer both aesthetic appeal and energy efficiency, Crittall’s W20 TE (thermally enhanced) steel window system is a fantastic example. This is because it achieves exceptional U-values of 1.4 W/m²K without compromising the distinctive minimal sightlines synonymous with original Crittall windows and doors.

Revolutionary engineering: the Crittall W20 TE system

The Crittall W20 steel window profile has long been recognised for its great versatility and characteristic slim sightlines appearing in everything from historic renovations to contemporary new builds. However, the introduction of modern thermal performance requirements (Part L) meant some changes needed to be made to this classic system.

Rather than abandoning this popular profile used to manufacture both steel windows and steel doors, Crittall’s engineering team developed an innovative approach to enhance the thermal performance of this system while maintaining its distinctive appearance and structural integrity.

Technical breakdown: how W20 TE achieves superior U-values

Innovative profile adaptation

The fundamental innovation in the W20 TE system is that it’s a patent-pending adaptation of the Corporate W20 steel profiles. Unlike conventional thermal break systems that physically separate the interior and exterior portions of the frame, the W20 TE employs a sophisticated profile modification that creates a thermal gradient across the profile equivalent to that of a thermally broken steel section.

This approach preserves the inherent strength of steel while dramatically reducing heat transmission through the frame. The result is a window system that delivers exceptional thermal performance without sacrificing the robust structural properties that make steel windows and steel doors ideal for demanding applications.

Dual weather seal technology achieving superior weather performance

A critical component of the W20 TE’s superior thermal performance is its innovative dual weather seals. These precision-engineered seals create multiple barriers against air infiltration and heat loss, significantly enhancing the window’s ability to maintain consistent interior temperatures regardless of external conditions.

High-performance glazing integration

While the changes to the frame and weather sealing are responsible for achieving the W20 TE’s impressive U-values, the system’s integration with high-performance glazing units also plays a crucial role.

The W20 TE is designed to accommodate advanced insulating glass units that further enhance thermal performance. This means architects and developers can successfully meet specific project requirements while maintaining the distinctive Crittall aesthetic.

W20 TE’s strength and security credentials

As a system which has been built upon the robust foundation of Crittall’s renowned steel profiles, the W20 TE offers a high level of strength, durability and security. Achieving enhanced security makes the W20 TE a reliable and secure steel system, offering properties owners complete peace of mind.

Practical applications: where W20 TE excels

Commercial applications and advantages

The W20 TE system works incredibly well within commercial settings where energy efficiency, durability and aesthetic appeal must be balanced with practical considerations of cost and maintenance.

Plus, available in a range of colours means this steel system can perfectly match any interior trend or exterior architectural style. In office developments, for example, the system’s slim profiles maximise natural light, creating bright and welcoming workspaces that don’t need to rely on artificial lighting.

Within retail environments, the system’s incredible versatility and design flexibility means it can effortlessly achieve a striking aesthetic, while its outstanding thermal performance creates comfortable shopping experiences for all visitors.

In educational and healthcare facilities, the system’s durability, strength and security is perfect for building spaces that stand the test of time.

Residential new builds and home renovations

In residential properties, the W20 TE system is a fantastic solution for both new builds and historical home renovation projects.

For those looking to achieve a more traditional feel in their property, W20 TE windows can replace deteriorated original steel windows in period homes while maintaining authentic character and dramatically improving thermal performance. This balance is difficult to achieve but is incredibly valuable in areas where preserving the heritage is essential.

In contemporary homes, clean lines and industrial chic remain a popular design choice for architects and homeowners alike. The W20 TE system not only has a distinctive finish, but it also achieves fantastic energy performance, creating spaces that have both visual impact and practical functionality.

Responding to changing building standards

As building regulations stipulate more advanced performance requirements, Crittall Windows remains committed to staying ahead of the curve and the W20 TE system is testament to this. By achieving U-values of 1.4 W/m²K, while maintaining the distinctive traditional steel aesthetics, this innovative system offers architects, developers, and conservation officers a solution that truly delivers the best of both worlds.

Can W20 TE system meet future building standards?

The Crittall W20 TE system achieves U-values of 1.4 W/m²K. This level of thermal performance already meets and, in some cases, exceeds current UK building regulations and positions it well for anticipated stricter future standards.

For projects requiring a balance of heritage aesthetics and contemporary performance, the W20 TE system provides an unmatched combination of visual character, thermal efficiency, and long-term durability.

As buildings continue to evolve toward greater sustainability and energy efficiency, the W20 TE system ensures that the distinctive character of high quality steel windows and doors can continue to be a defining feature of exceptional architecture for generations to come – a legacy of engineering innovation and timeless design.

Crittall Windows: classic elegance and enduring quality

Crittall Windows holds a solid reputation built on 175 years of crafting beautiful steel windows and a comprehensive steel door range. Their commitment to providing custom window solutions and bespoke door designs ensures a perfect fit for any project, while the availability of a full range of colours and various finishes allows for seamless integration with any architectural style.

With an extensive range of profiles, Crittall’s steel systems deliver exceptional performance and a cohesive look throughout any building. Timeless Crittall products continue to be an incredibly popular choice for those who appreciate enduring quality and sophisticated aesthetics.

Get in touch today to discover more about the W20 TE system and how it can be used in your next project. Alternatively, explore the full range of Crittall steel windows and Crittall doors today.