The new Sainsbury's supermarket in Greenwich is a hit with the public; last year they voted it into the finals for the Stirling Prize. It is also designed to a serious environmental agenda and lays claim to be the most energy-efficient supermarket ever built. The building uses up to 50 per cent less energy than a standard store and has achieved an 'excellent' rating by the BREEAM assessment method.
And it looks good -the main entrance is flanked by curved walls of untreated oak boards and sheltered with an aluminium brise-soleil. The roof is a gentle, almost imperceptible, barrel vault of stuccoembossed mill-finished aluminium with standing seams, punctuated by rows of sawtoothed rooflights. At the sides of the building the walls are protected and insulated by ramped earth banks, planted with turf.
The application of low-energy environmental design techniques to a relatively untried building type - a supermarket - was developed by both client and architect.
The key element to energy saving was the aluminium roof. 'It's the fifth elevation really' explains Paul Hinkin, project architect, 'and because a supermarket sales floor is basically a huge deep-plan space, you need to use the roof as an active facade to get air out and light in'. The roof admits natural light through eight north-facing saw-tooth rooflights which run almost from one side to the other in a gentle arch over the 3,112m 2sales floor. They are high-performance double-glazed windows in aluminium frames which are fitted with external horizontal aluminium louvres.
The sales floor is heated by underfloor heating pipes, acting, in effect, like a giant radiator. Heat is generated on site by means of a gas-fired combined heat and power plant. An ingenious passive ventilation system draws air from under the earth-banked side walls and into the sales floor through grilles at the bases of the display shelves. It rises naturally and is exhausted through continuous vents located at the head of each saw-tooth rooflight.
Computer sensing technology is used to control both natural light and ventilation.
The external aluminium louvres are operated by a Building Management System (BMS) to limit levels of daylight and prevent light 'pollution' of the night sky. The air-extract vents are controlled by a damper system operated by the BMS to regulate the rate at which air is exhausted. During the day the store is lit by natural light, with the only permanent artificial lighting positioned directly over the goods and fixed to the display shelves.
The standing-seam aluminium roof profiles were manufactured on site by Euroclad in specially designed trailers; this allowed long lengths of roof sheet to be produced from coil, without the difficulty of handling, packing and transport to site. Profiled sheets as long as eighty metres were used to cover part of the store roof.
The aluminium roof and its associated windows and louvres make a positive contribution to the energy saving systems of the building. It was chosen as a material which would provide a long life with low maintenance. 'We were anxious to specify materials which would not require any sort of staining or treatment' explains Hinkin, 'the stuccoembossed mill-finished aluminium is inherently weather-resistant and will mellow in time'. Aluminium is one of the most abundant natural materials on the planet but the smelting process involves energy use; all aluminium components on the building contain recycled material and are capable of being recycled again at the end of their working life.
ARCHITECT Chetwood Associates: Laurie Chetwood, Paul Hinkin, Steve Burr, Richard Darvill, Daniel Tung
STRUCTURAL ENGINEER WSP Consulting Engineers
SERVICES ENGINEER Oscar Faber
CONSTRUCTION MANAGER RGCM SUPPLIERS standing-seam aluminium roof Euroclad; aluminiumframed roof glazing and louvre system Colt