Last edited 19 Jan 2021

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Underfloor air conditioning at London Grade II listed landmark



[edit] Introduction

AET flexible space was specified to supply its innovative CAM-V underfloor air conditioning (UfAC) system for the refurbishment of 24 St James’s Square, completed in early 2020. The design brief was to maximise floor-to-ceiling heights and enhance the double aspect interior. One of the key challenges was the need to preserve key architectural features, whilst at the same time providing flexible, modern, premium office space.

These needs could not have been met using a conventional overhead system, which would have taken up valuable headroom and created awkward junctions where window heads met suspended ceiling grids or exposed services.

[edit] Creating a ventilation path

Using an underfloor air conditioning system enabled the designers to eliminate ceiling-based services allowing for a plasterboard ceiling to be installed tight against the soffit and down stand beams. Thanks to the AET system, key architectural elements of the building were preserved, as well as increasing natural light levels and enhancing the striking double-aspect interior.

“The AET downflow units promptly stood out as the obvious candidate for several reasons, including having the absolute minimum requirement for floor void height, and offering excellent distribution of cooling, heating and ventilation evenly across the whole floor whilst reducing energy consumption,” says M&E Consultant, Vic Holloway with Edward Pearce LLP.

AET’s UfAC systems make use of the space beneath a raised access floor to create a ventilation path, eliminating the need for ceiling-based mechanical services helping to maximise the floor to ceiling heights and creating a brighter and more and airy office environment.

[edit] Project specifics

A mix of CAM-V22 and 33 units were installed across the eight floors of office space. Roof mounted high efficiency heat pump units serve the refrigerant coils in each of the CAMs. Conditioned air is delivered into the space via AET’s market leading TU350 slimline Fantile™ units which sit 160mm within the floor void.

To avoid unwanted grilles at high levels, AET designed bespoke floor extract grilles that look identical to a Fantile™ unit to allow room air to be extracted directly from the floor void. This enabled the interior aesthetic to remain consistent and simplify duct routes within the building’s core.

[edit] Addressing complaints

Common complaints from staff prior to the refurbishment were variations in temperature across the office space, high level cold draughts and a lack of natural daylight light. The UfAC solution provides greater individual control of localised temperature, unobtrusive movement of air and more comfortable, brighter working environments.

The 24 St James’s Square project won the Best Office Architecture London award at the 2019 International Property Awards and was shortlisted for Retrofit Project of the Year at the H&V News Awards 2020. The building is being let as Grade A office space by BNP Paribas Real Estate who advised the developer, Misland Capital, to consider AET’s system based on their positive experience with 28 Saville Row, which AET completed in 2014.

This article originally appeared in the Architectural Technology Journal (at) issue 134 published by CIAT in Summer 2020 under the headline, '24 St James’s Square, London'.


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