Thinking big.

A prototype for high-rise ecologically aware buildings, this mixed-use tower in Shanghai suggests ways of marrying green concerns with commercial viability.

Kenneth Yeang is already well known for his experiments with ecologically appropriate towers, some of which have been shown on these pages (ARs February 1993 and September 1994). Up to now, he has not built anything more than 15 or so storeys high, but this new proposal for Shanghai has 36 floors and, though far from being very tall, carries his 'bioclimatic' ideas further than before, both in scale and complexity. It suggests ways of extrapolating the ideas to higher structures, which have been thought by many to be impossible without a totally air-conditioned sealed envelope. Yeang does not suggest that air-conditioning can be done away with completely, but that his proposals will temper the need for it, and hence reduce fuel use and carbon dioxide production. The tower houses a hotel topped by offices, with an exhibition hall and auditorium for 300 people slung in at levels 17 and 18. It is one of those stacked Chinese urban buildings in which functions are piled above each other - the sort that used to give Hong Kong such vitality.

Shanghai has a maritime climate with quite cold winters and hot summers. A heat exchanger will enable the mechanical ventilation system to minimise energy loss from exhaust air in extreme periods. Mass and insulation will be used to exploit the thermal fly-wheel effect. A double skin facade with movable horizontal louvres between the layers will moderate the internal climate by providing an insulating jacket of still air in winter and a stack effect in summer on to which windows can be opened (the outer skin acts as a sun modifier). In summer, spring and autumn, central vertical atria linked to planted (hence oxygenating) sky courts will provide the main driver of the ambient energy system, acting as a thermal chimney assisted by the venturi effect, and allowing cross ventilation in the hotel corridors and offices. A big external wind-breaker will deflect cold north-west winter winds, and in that season the building's skin will be largely sealed to prevent heat being wasted.

The Armoury Tower is intended to evoke resonances with traditional Chinese military kit. For instance, the metallic screens refer to armour; the solar panel on top, a helmet and, Yeang thinks, 'the stair plan suggests the trigger of a gun'. The building, he says, 'is intended to create a modern urban icon for the client's progressive and valiant march into the twenty-first century'.