Foster in Frejus.

A school in the south of France that makes best use of local building expertise to create a structure that is ventilated and largely heated by ambient energy.

The new Albert Camus Lycee Polyvalent at Frejus is an example of an interesting French school type which offers both academic and partly vocational education for people in their last three years of schooling. A long thin silver Euclidean streak, it sits on a hillside on the Cote d'Azur, ranged east to west with marvellous views south to the sea, and to the north up the dry, raddied sweet smelling hills.

It is an artefact that makes no immediately obvious concessions to its immediate environment: like the work of the Ancients, it seems to sit as a perfect object in a natural landscape. Yet it is far from being as simple as it seems at first sight. The plan is double-banked along a central route which is too grand, wide and tall to be described as a corridor, for it is top-lit and two stories high, with the upper level defined by balconies on each side. Bridges connect the two sides at intervals, while the balconies themselves fly bridge-like over the double-height entrance hall that drives a wide and generous counter-axis through the building at right angles to its main east-west alignment.

This internal street is not, in fact, in the centre of the long thin plan. To its north is a range of specialised teaching areas that need various forms of technical back-up, which makes this side of the plan deeper than the southern range of rooms devoted to 'enseignements generals'. These spaces are connected to the view and protected from the heat of the sun by a most generous sweeping canopy of brises-soleil cantilevered from the main concrete structure. Under the lozenge-sectioned perforated-metal fixed louvres, the ground floor general classrooms each have a particular outdoor summer space on which dappled sunlight plays. Above, classrooms look out through the louvres, the view to the sea striated and made particular by them.

The brises-soleil are only the outward manifestation of the building's complex passive response to climate. The structure is in-situ concrete, chosen by the architects as a technique which offered both high thermal mass and a very good chance of being well made, economically, by local contractors. (The finish of the concrete is unusual in a building of this kind: it was achieved by repetitive use of first-class steel shuttering.) The roof structure is formed as a series of shallow transverse vaults which curve towards the central double-height space. The concrete vaults are covered by a longitudinally curved corrugated steel roof which is detached from the insulated concrete, allowing cooling air to be drawn from eaves to apex.

The shape of the cross-section is a device for encouraging convection. The clerestories over the long communal spine are opened at most times, except the coldest. The central double-height volume acts as what the architects call a 'solar chimney'. Hot air is sucked out by both convection and the Venturi effect of wind passing through the Iouvres of the clerestories.

The clerestory sides can be opened separately to respond best for different prevailing winds: the Mistral and the Mediterranean breeze. In cold times, the whole system is shut down to provide an impervious carapace.

The basic diagram of the building may seem a bit prison-like, but the school plainly works well, and it is enjoyed by its users: students and teachers both.