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st'jctural design

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Tower of Babel

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rainwater purification sy*ter

A prototype for a new generation of high buildings in the tropics, this Singapore tower explores Yeang's principles of bioclimatic design more extensively than ever before, it adds many new ideas and contextual touches.

Yeang has long hern associated with tall eco-friendly projects, what he calls bioclimatic skyscrapers (see for instance AR February 1993 and AR September 1994) But up to now. though his buildings have shown steady evolution, they have been constrained by clients with understandably quite restricted programmes The chance to try out ideas on a more speculative, yet possibly achievable level has come from a proposal by the Singapore Urban Redevelopment Authority who asked him to make proposals for an exhibition tower one that could contain exhibition spaces of all kinds, retail uses, and auditoria This is projected to be what he calls "a prototype ecological building design" in which his green ideas can be pursued with more freedom than usual, and with greater rigour, over a wider range of issues of ecological concern.

At the |unction of Waterloo and Victoria Streets, the site is not far from the fabled cluster of slender (and by no means inelegant) towers that heraldically symbolize Singapore's CBD. But when this 26-storey structure is built, it will be completely different from them: it will be covered with vegetation, eroded to allow for internal terraces and sky courts, brimmed with shades, helm-masked with shining solar panels and wrapped in ramps The latter are intended to make 'vertical places', gently and easy transitions between levels of what Yeang calls the "inevitable physical compartmentation of floors inherent in the skyscraper typology" The most important ones run up the lowest six or seven floors to make what Yeang hopes will be a "vertical extension of the street". Wide landscaped ramps conduct you upwards from road level, and are lined with street activities like stalls, cafes, shops, bars and so on; they lead onto the lower levels of the great exhibition building. The aim is to recreate the wonderful mix of uses, people and spaces which made streets of the richer cities of South-East Asia (Singapore, Hong Kong, and to some extent Kuala Lumpur) magically alive in the middle of this century. The buildings were modern concrete structures, but the wild mix of functions (from department stores to housing, restaurants to workshops) was far more varied, lively and picturesque than anywhere else (sadly, modern development has replaced many of these wonderful but shabby tenements with uni-functional object buildings).

Yeang's towers have always been intended to be shaggy, intimately related to vegetation, which he uses not only as an amenity bit as a means of providing shade and improving interior microclimate and oxygenation In the Singapore pro|ect, he proposes to go further. He regards the site as ecologically "devastated", and has carried out a survey of local species to find which plants will be most suitable for the new building, and re-evoking the original eco-system. They are to make a continuous garment from street to crown of the building, winding through the ramps and vertical places. They will be nourished by rain which will be collected on the roof and in a series of "scallops" on lower floors Rain will be augmented by grey waste water and the two will be filtered and kept in a tank on the roof to feed the irrigation system and lavatory cisterns.

The plants will be the only climate modifiers. Of course, there will be air conditioning, but its use will be minimized by built-in shading, fixed and movable, and by wind walls placed parallel to the prevailing wind to direct breezes to sky courts and internal spaces. Ceiling fans with de-misters will be used for cooling before the full air-conditioning system comes into play The photovoltaic arrays are intended to reduce demands on the national electricity grid to power refrigeration and lighting. Solar thermal collectors will head most of the domestic hot water.

One of the key concepts behind the building is loose fit, an idea that has been around for three or four decades, but which is rarely a conscious determinant of design. Yeang suggests that the tower could be converted wholly or in part to office or residential use, and has prepared a scheme for converting the entire building to offices at 75 per cent net to gross efficiency Partitions and even floors will be removable, but solid enough to provide sound insulation where necessary

Yeang also believes that the whole thing should be capable of being demolished with minimum waste of energy and materials Hence, he proposes making all structural joints by mechanical rather than fusion methods (that is, in the case of the frame, bolting the steel rather than welding it) So the structure will be demountable and rc-usable, and so will elements like the floors, which he suggests will be made of innovative structural timber cassettes

There arc numerous other ingenious ideas in the concept for instance methods of handling the building's waster (such as packaging and unused food), and composting solid sewage It will be marvelous If the whole proposal can be realized, but even if only thiee quarters of the ideas are implemented, the shaggy tower should be an example for development in all tropical regions rainwater purification sy*ter

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