Activity centre benefits from natural ventilation from Gilberts

The environmental impact of a £15m, 4000m2, three-storey activity centre in the heart of the Surrey green belt, within a Grade II listed park, is being controlled by optimisation of natural resources, including a natural ventilation strategy from independent air movement specialist, Gilberts Blackpool.

Working on the design and build project for contractor, Blenheim House Construction (BHC), Gilberts has produced a natural ventilation strategy to a bespoke design, to ensure the ‘architecturally-dramatic’ new activity centre at St George’s School, Weybridge, will be appropriately aired, irrespective of occupancy and activity levels within, and with minimal impact on its external surroundings.

BHC project surveyor, Joe Anderson, said: “The project was a challenge that we were confident Gilberts could meet.

“The site geography provided challenges: the building has been sunk into the surrounding landscape to give level approaches at ground and second floor – there’s a height difference of at least 8m – which impacts on airflow around the building.

“Gilberts also had to deal with the ventilation’s ability to cope with occupancy and activity differences ranging from a whole-school assembly of 1,000 or more pupils and staff, through to part of a class using the climbing wall or cricket nets. It had to balance human occupancy and activity alongside the potential heat gain as a result of large areas of the building featuring floor to ceiling glazed sections.

“Beyond the technicalities, the ventilation had to reflect the high aesthetic standards of the project.”

With its in-house design and manufacturing capability, Gilberts was able to engineer a tailor-made rooftop ventilation terminal (penthouse) design to deliver the required air flow and a weathertight fit onto and through the omni-directional curves of the roof. In total, 16 PHH75 roof terminals, each 1900mm x 100mm x 14mm, with boost fans in those over the main sports hall area, have been fitted to the Glulam beam and CLT panel roof. Almost all of the penthouses provide natural ventilation into the sports hall below; those over the lower areas of the roof feature additional fan assistance to ensure adequate delivery of fresh air in their more sheltered location.

On the four vertical facades, 30 x Mistrale façade WHC75 high performance ventilation louvres in a deep channel frame have been integrated into the rainscreen cladding to provide ventilation to the café, viewing platform, fitness suites, studio, toilets and changing rooms. Louvres up to 5570mm x 800mm were produced to create an aesthetic solution.

A further 12no louvres providing air for the sports hall also include LTHW heating coils, to reduce temperature differentials between fresh, incoming air and the existing internal atmosphere, and deliver appropriate quantities of fresh air across the 30m clear spans within the main hall.

A further 2no WHC75 provide screening and ventilation to the rooftop plant, and 2no louvre double doors ventilate the switch room and plant room.