Canon Headquarters (UK), Reigate

Situated on a quiet sheltered 25-acre site, the 11,500m² of office space has been designed in sympathy with its surroundings, taking advantage of natural ventilation which is ideally suited to the unpolluted environment. The ventilation strategy works in unison with a coffered slab to provide passive cooling. Night ventilation is used during hot weather, controlled by a simple BMS algorithm that follows BSRIA recommendations.

Stack ventilation is also provided by a central atrium. The building has been orientated to minimise solar gains and a 3m roof overhang structure with cloisters keeps out direct sunlight while minimising the need for artificial light. West and east-facing windows have external shading that is automatically controlled to prevent excessive solar gain in the morning and evening.

Working areas are open-plan and comprise a narrow floor plan of 11m on three levels, with a central atrium and an open balcony arrangement. This ensures that all workstations receive a high level of natural light and that there is minimal restriction to air flow. This is particularly important with stack ventilation which, although effective with atria, only offers a very small driving force that is easily disrupted by obstructions.

To improve air flow across the soffit, downstand edge beams were substituted with upstand edge beams within the raised floor. Occupants can open perimeter windows, whilst clerestory and atrium windows are controlled by mechanical actuators linked to the BMS. Heat-producing office equipment such as photocopiers have been grouped together in a controlled area with cooling provided by fan coils served by a single chiller, which also provides cooling to meeting rooms and a lecture theatre.

The background ventilation uses a two-speed fan system that delivers air to swirl diffusers in a raised floor. These produce a column of air and avoid pooling, making supply temperatures as low as 15°C possible without discomfort. Return air is via extract grilles located at the top of the atrium. These can be accessed from a high-level balcony situated above the second floor. This is at the same level as five roof-mounted air-handling units.

The post-tensioned coff ered slabs were cast on site in re-usable moulds which were a cost-effective option given the number of reuses. The troughs were designed to work in unison with suspended luminaires incorporating acoustic wings to reduce reflected sound from the soffit. The surface finish is of a high quality and has been painted white to aid daylight penetration. The building achieved a BREEAM rating of ‘Excellent’.