Case Study: 42 Berners Street – Underfloor low level services permit additional floor and flexibility at fit-out
Leading provider of underfloor air conditioning systems, AET Flexible Space, has completed the supply and commissioning of underfloor air conditioning equipment at 42 Berners Street, Fitzrovia. The 27,300 sq. ft. building, part of the Berners-Allsopp Estate is a high quality new build development created through the demolition of two town houses, offering 22,000 sq. ft. office accommodation on five of the seven floors and retail at basement and ground level.
Architect – Buckley Gray Yeoman
M&E Consultant – GDM Partnership
Main Contractor – Kind & Co.
M&E Contractor – MSL
The redevelopment was designed by architect Buckley Gray Yeoman, with mechanical services specified by consultant, GDM partnership. The design brief included a number of key challenges such as maximising the footprint of the building, the internal lettable area and, most importantly, internal floor to ceiling heights. Westminster council also imposed local building height restrictions on the development and the design was stipulated to fit sensitively within the historic Berners Street surrounds.
A high level services strategy is often perceived to be a more “traditional” method of distributing services within office space, however, a services zone dimension in the ceiling space is required to accommodate the ventilation ductwork, terminal units, pipework and associated power supply provision, and if these services are to remain exposed and on view, this would require a heightened level of co-ordination to provide a tidy aesthetic installation, challenging at the best of times. By adopting a low level services strategy, equipment is installed within the plenum beneath the raised floor, which effectively becomes the ventilation zone.
This space saving design permits reduction in slab to slab height, which, when calculated across a development can equate to the creation of an additional floor for the building. Floor based air conditioning can be attributed to height savings in new build construction, clearly shown at the 42 Berners Street redevelopment where an additional floor was created, yet still within the imposed planning height constraints.
Underfloor air conditioning was put forward as a mechanical services option that could help meet the aspirations of the planners, and by adopting a low level services strategy, designers were able to increase the available space, adding a seventh floor to the building originally designed with six, and maximising the internal headroom on each floor.
There are two different types of underfloor system, the first being a full underfloor solution, with CAM-C zone units supplying conditioned air, and receiving spent air via the plenum beneath the raised access floor. The plenum effectively becomes the ventilation zone and the underfloor void is divided into supply and return air paths using fire-resistant, air-tight silicone cloth. This first system is undoubtedly the best option if the brief is to expose ceilings and maximise headroom in refurbishments as it allows total elimination of any ceiling void. By doubling up the use of the underfloor plenum, space savings can equating to approximately 400-500mm per floor.
Another low level services option is a system with a CAM-V zone unit which supplies conditioned air via the floor plenum, but receives spent air at high level or via ceiling extract grilles. As there is no need to divide the floor plenum, this option permits freedom to maximise the floor plate as well as future flexibility due to the ease of reconfiguration.
The system specified at 42 Berners Street is a CAM-C direct expansion system, connected to roof top VRV heat pumps, and installed throughout the five office floors. The design has been zoned according to the specified Cat-A layout, with each floor divided into two separate zones and each zone served by a CAM-C25 downflow unit. The Fantiles supplied are typical TU4-EC fan terminals which recess into the 300mm underfloor void. Only requiring power and data connection, and designed to replace a standard 600mm floor tile, the Fantiles can easily be re-positioned to suit incoming tenant requirements.
The zone layout is a typical configuration, with the underfloor void segregated using air baffles into a perimeter supply air path, and a central return air path. The CAMs were positioned within aesthetically designed cupboards, concealing essential ductwork and piping, and also providing further acoustic barrier.
The project is also the first site to receive the latest release of the Flexmatic Touch display. Installed within the CAM zone units enabling access to the unit control board, the Flexmatic Touch display can be used independently to monitor and control each zone of data linked CAMs and Fantiles, or, as seen at 42 Berners Street, networked together and connected to the main BMS via a Flexgateway interface.
Witnessing the finished Cat-A installation, Project Manager of Main Contractor, Kind and Co., Andy Munn commented on the quality of the underfloor services, that he was, “particularly pleased with the noise levels and the temperature stability of the CAM-C system in operation”. Practical completion was achieved in December 2018 and the site is expected to be awarded BREEAM status “Very Good”.
The building with its new Portland stone façade and bronze windows has made a significant contribution to the Fitzrovia street-scape, setting the precedence for pipeline developments. Creating the flexible grade-A office accommodation has proven to be a positive strategy. The property owners were in lease negotiations with a single high profile client prior to practical completion and AET Flexible Space are currently working with the new client team on the Cat-B fit-out to help ensure continued flexibility in operating the underfloor services