Mott MacDonald provided building services design. This included specialist and natural lighting, building physics and sustainable low energy solutions.
The internal building in the Darwin Centre consists of a 35m tall glazed box which houses an eight storey cocoon, like a specimen in a glass display case. The cocoon protectively envelops the museum’s collection, state-of-the-art laboratories, visitor centre, exhibition space and lecture theatres.
Stable archive conditions were needed to optimise the environment in circulation spaces and in research laboratories so that specimens could be protected as much as possible when removed, viewed and handled.
Precise management of the centre’s climate was also key to eradicating a major hazard, the museum beetle, which feeds on organic matter. We calculated the optimum control point, 17ºC – not too cold to work in, but cold enough to prevent the beetles from reaching sexual maturity. Relative humidity was fixed at 45%.
We achieved a low energy solution by harnessing the site’s existing resources and working with architect CF Möller to exploit the building’s structural design for ideal energy efficiency.
The cocoon is buffered from outside temperatures by the space between the inner and outer structures. Initially, the atrium was to have been naturally ventilated, but concerns about pollution build-up led to adoption of mechanical ventilation instead. Rather than condition the entire space, air handling units were placed beneath the floor, pushing a small amount of treated air into the 2m immediately above. We focused on the area occupied by people.
Temperature and humidity in the cocoon are controlled using purpose built air handling units. Heat, cooling and power are supplied by the Natural History Museum’s central combined heat and power plant and absorption chillers.
An energy recovery system recycles around 75% of thermal and latent energy from exhaust air back into supply air. Walls and floors of the cocoon itself are concrete. Insulated on the outside, the concrete is exposed on the inside. The concrete provides a stabilising thermal mass. Collections should remain at suitable storage temperatures for many hours even if the ventilation systems are switched off.
We achieved additional energy savings through lighting design. In the corridors of storage areas, lights are activated by movement sensors. In storage cabinets lights dim automatically after 40 minutes. In the laboratories, artificial lighting automatically adjusts according to how brightly the sun is shining.