WS Swift, a specialist in HVAC system upgrades and mechanical pipework in London, has completed a live retrofit project at 1 Stephen Street — a landmark 265,800 sq ft office and retail building. The project involved upgrading the existing chillers to air source heat pumps as part of a drive toward more sustainable construction practices in London.

Carried out while the building remained fully occupied, the retrofit required innovative solutions to meet both performance and safety requirements.

Delivering a Live HVAC Retrofit in Central London

Undertaking a large-scale HVAC retrofit in an operational building presents significant challenges, especially in London’s high-demand commercial property sector. WS Swift needed to avoid disruption to tenants, minimise installation time, and ensure safety on-site — all critical in a live building retrofit environment.

By partnering with Victaulic, WS Swift adopted a flame-free pipe joining system, eliminating the need for welding. This method reduced installation time, removed the risks associated with hot works, and allowed for easy pipework modifications during phased commissioning.

“Victaulic’s system allowed us to adapt quickly on-site, ensuring we could meet project deadlines without affecting building operations,” said Chris Rodwell, Mechanical Project Manager at WS Swift.

Overcoming Retrofit Challenges with Flame-Free Pipework

The retrofit required maintaining continuous cooling while phasing out the old chillers. WS Swift used temporary cooling systems, which could be easily repositioned and reconnected using Victaulic’s modular pipework, offering essential flexibility.

“We had to run parts of the old and new systems together. Victaulic’s flexibility allowed us to adapt the system live — keeping everything operational and on schedule,” said Daniel Swift, Managing Director of WS Swift.

Safety was also critical. Victaulic’s mechanical joining system eliminated hot works, reducing on-site hazards and ensuring compliance with strict safety protocols in a busy commercial environment.

Precision Planning with Digital Pipework Modelling

To ensure seamless installation, WS Swift worked with Victaulic’s Virtual Design and Construction (VDC) team to convert traditional welded pipework designs into a grooved mechanical system. This detailed digital modelling helped avoid clashes, optimise prefabrication, and ensure materials were delivered precisely when needed.

“Having the VDC model meant we could plan every joint and avoid surprises on-site,” said Chris.

Supporting London’s Drive for Decarbonisation

With decarbonising London’s buildings a key part of the city’s climate strategy — particularly through the Accelerated Green Pathway and the push for 2.2 million heat pumps by 2030 — projects like 1 Stephen Street highlight how smart retrofit solutions can transform existing infrastructure sustainably.

Mechanical pipe joining systems like Victaulic’s contribute to low-emission construction by reducing installation impact, enabling reuse of components, and supporting the circular economy through recyclable materials.

“This project proves that by combining new technology with smart planning, we can decarbonise existing buildings while keeping them operational,” Daniel added.

A Blueprint for Sustainable HVAC Retrofits in London

The successful HVAC system upgrade at 1 Stephen Street demonstrates how thoughtful engineering, collaborative planning, and innovative technology can overcome the complexities of retrofitting occupied buildings. As the demand for sustainable HVAC upgrades in London grows, this project sets a benchmark for future retrofit work.