Southampton Landmark Back on the Map After Residential Window Wall Transformation

Location	Southampton
Fabricator	Mega Glaze
Year	2024
Product	GENEO Tilt & Turn

Change-of-use building projects continue to dominate the retrofit agenda due to the many built environment challenges they can help to solve. However, technical collaboration and know-how are crucial to ensure they are designed truly fit-for-purpose. Together, Mega Glaze and REHAU collaborated to develop a high-performing window wall solution that would stand the test of time for legendary mapmakers “Ordnance Survey” HQ in Southampton.

Compass House is a landmark building in Romsey Road, Southampton, and has a rich history of commercial use dating back to 1969 when it was first opened by Queen Elizabeth II as the ordnance survey headquarters. Thirty years later it was taken over by HMRC before being purchased by a developer in 2019 who then submitted a transformative change-of-use proposal as there was no longer a commercial need for the space. Today it boasts a mix of 245 contemporary one- and two-bedroom apartments, finished to a high-quality specification. Yet its transformation was no mean feat.

Change-of-use conundrum

While change-of-use projects partly provide a solution to the UK’s housing crisis, as well as a key pathway to the decarbonisation of old buildings, they do not come without their design challenges – particularly when it comes to windows.

The commercial nature of Compass House’s vast, square, four-floor design was not typical of a multi-residential space found in the UK, which would usually be over a higher number of floors or spread over multiple buildings. In particular, the non-purpose-built openings were significantly over-sized for a residential application, and the 1km circumference presented various logistical challenges.

Klifer Developments was appointed as the main contractor and brought in the support of its long-standing commercial window installation partner, Mega Glaze, for its experience working on such projects to design a solution that would make the building fit-for-purpose.

The criticality of pre-specification

The mid-century building featured a window wall, similar to a curtain wall but with the windows sitting between floor slabs and anchored at the sill and head. With thermal performance acting as a key driver, uPVC windows were specified as the material of choice, yet finding the right style of window that could satisfy the larger sizes, as well as knowledge around such an unusual uPVC application, was another hurdle to face.

It was at this stage that Simon Benesh, Director at Mega Glaze, consulted with his preferred uPVC window supplier, REHAU, confident in the company’s extensive technical support and premium profile. Steve Tonkiss, Head of Sales South at REHAU was key to this process and provided all the necessary requirements for the developer to get it through the Council’s stringent planning process.

There was a multitude of pre-specification factors to consider. Firstly, it was important to assess the potential expansion levels of the uPVC to ensure the building remained structurally sound throughout its lifespan. Then the coastal weather patterns needed to be reviewed to conduct wind load calculations – it became evident at this point that the west elevation, for example, would see higher water exposure.

There were also several fire safety considerations to be made with this scale of refurbishment project, not least because of the change in occupancy levels, but also factoring in that older buildings would have been originally designed with outdated fire safety measures.

And after all, it’s a window wall

Steve, Simon and the team set to work to design a highly efficient, safe, easy-to-install, and aesthetically pleasing solution that would tick all the boxes. The answer lay therein REHAU’s TOTAL70 windows in anthracite grey outside and white inside, with automatic opening vents (AOVs) by each of the four stairwells to meet fire safety requirements, as well as the glazed aluminium panels being A1 fire rated.

While the legislation relating to fire safety and smoke control were the most important in terms of occupant safety, AOVs could also affect the U-values of windows. Nevertheless, REHAU was able to design a window solution to a high-performing U-value of 1.31.

The window wall design also required the use of expansion couplers which would allow the window to contract and expand, which REHAU was able to supply as a holistic solution.

In total, 2,795 glazed areas were supplied via 1,227 uPVC frames and 1,071 pieces of glass.

A team fit-for-purpose

One of the biggest challenges of a project involving such a high volume of heavy product – due to the steel reinforcement of the windows – across such a large site, was logistics. Mega Glaze assigned a sizable team of installers and executed a meticulously planned logistics programme with seven storage containers strategically placed across the site for easy access.

REHAU’s technical team was also on hand every step of the way. Paul Evans, Technical Support Engineer at REHAU visited the site regularly to assist the fitters and ensure everything was within guidelines, particularly relating to the more challenging expansion couplers.

This level of collaboration resulted in the work being completed in just four months, as the installation work began in the January and was completed by April ahead of residents moving into the first phase by July.

Simon Benesh, Director, Mega Glaze commented: “The support the REHAU team provided on this project has been second-to-none. They have the knowledge to apply uPVC to commercial buildings, which not a lot of companies do at this level. We do a lot of change-of-use buildings and they’re always guaranteed to throw up challenges you wouldn’t have thought of, so having the right partners in place to uphold the highest of standards is paramount. These days, we only use REHAU for uPVC due to this excellent level of service and range of ancillaries available, such as the expansion couplers, because we know we can get everything in one place.”

Steve Tonkiss, Head of Sales South at REHAU, added: “Well, what a project this was! The technicalities were a real test, but we loved every moment of the challenge and were delighted to take it on. We have an unparalleled team of technical experts here at REHAU, who all know just how important it is to go above and beyond on a project like this. uPVC windows have a strong place in the future of sustainable retrofit and we’re loving every moment of showcasing this.”

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