There were two drivers of this design. One was a desire to make the building as environmentally friendly as possible. The other was to fit as unobtrusively as possible into an inhabited area with a building that many would view from above, from housing on nearby hillsides.

‘Often these buildings just sit in isolation, but this one had to sit in its community,’ explained Tim Wood of Chetwood Architects. To minimise the impact, the architect partly buried the building in the hillside, and used the earth that had been dug out to create mounds to partially shield it from view. The curved form also grew from the sightlines and the desire to shield the building. This was the driving force for the roof’s single, low-pitched form.

With no valley gutters, the design had to use a combination of gravity and siphonic drainage to remove water from this vast area.

Prepainted metal was used for both the wall cladding and the roof covering. The selection of colours required a great deal of thought and experimentation. Traditionally, Gazeley, the client, uses a blue colour, but this works best for a building in isolation, set against the sky. Here the building would be looked down on from above, which led Chetwood to experiment with the idea of green. But, says Wood, ‘we were cautious,’ aware of the danger of a garish solution. They ran three-dimensional modelling programmes, and also worked with the manufacturers of the prepainted metal to come up with the eventual scheme of graduated greens.

Whereas a banding effect has been used on most of the walls to break up the mass, the upper half of the south-facing wall is a solid dark green.

This is because it is playing a vital role in the energy strategy of the building. This wall uses a clever insulated sandwich panel system which supplements heating in the building, and can reduce the heating load by up to 20%. The ‘crowns’ of the metal profiles are hollow, and air is drawn up through them, rising as it increases in temperature. At the top of the cladding, fans draw this warm air into the building. The darker the colour of the cladding, the greater the heat gain will be – hence Chetwood’s choice of a dark green.

ETFE skylights set into the roof, some with integral photovoltaics, enhance the daylighting of the building and reduce the need for electrical lighting. As well as savings on lighting and power, the building has a water usage that is 60% less than on a comparable building. The project also has planning permission for a biomass plant, although this has not yet been installed, and a decision remains to be taken about the capacity – either 5MW or 10-11 MW. Once this plant is installed, it will link to the underfloor heating for the building.

The architect looked very carefully at the sourcing of materials, selecting wherever possible those that had an A or an A+ rating in BRE Global’s Green Guide to Specification. The office element of the building is clad in FSC certified Western Red Cedar. All materials have been considered not only in terms of how they were sourced but also of how they will eventually be disposed of, with very little going to landfill. Most will be capable either of being recycled or of being re-used directly. All these factors contributed to it being the first building of it’s type to achieve a BREEAM ‘outstanding’ rating, an achievement in itself and even more so for a building type that is not conventionally thought of as environmentally friendly.

In every sense then, the Chatterley Valley distribution warehouse can be considered as a green beacon.

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