Title: Office beneath the skin

Pages: 18-23


Author: Martin Pawley

Text: Office beneath the skin

Computer Technology's office in an air tent might just turn conventional notions of building upside down. Martin Pawley describes how architects Foster
Associates have found a new use for inflatable structures. Photographs by John Donat.

Inflatables have been around for some time. Balloons date from the eighteenth century, airships from the nineteenth, covered life rafts from the second world war and building s from the AEC portable theatre of 1959. However what went up on a frosty Sunday morning in January outside Hemel Hempstead was something rather different - and it just might make the other milestones look like the short end of a millimetre scale.

For on that day - with a great deal of snap, crackle and pop - the world's first inflatable office building lifted off the snow covered ground to full inflation in 55 minutes. Designed by the architects, it broke new ground in consultancy, design and construction management. The envelope, a nylon and PVC fabric purchased from Swedish Polydrom via their British agents Youngman System Building Ltd. enclosed 8000 sq ft of unbroken floor space which now houses 70 programmers, designers, accountancy and management personnel from one of the fastest growing computer manufacturers in Britain - Computer Technology Ltd.

This firm, established in 1965 by five young design and development engineers has doubled its staff, accommodation and turnover every year since formation by concentrating on the development of the highly successful Modular One series computer-the only real time multi-processor modularity designed and built in this country. Expansion at this speed brought accommodation problems in Computer Technology's cleverly converted canning factory on the Hemel Hempstead trading estate (DESIGN 250/35-6). But the firm's plan to overspill into a brand new building in the adjoining plot of land ran into difficulties. The Board of Trade proposed a move to Scotland, and negotiations over the


The scene on blow-up day fast January, 1 6. Powered by 2hp motor, the nylon and pvc envelope rose off the snow-covered ground full inflation in 55 minutes. The air tent has one air-lock entrance, and three emergency exits. Those in a real hurry to escape can always slash an opening in the fabric.


Plan, left shows phases 2 of Computer Technologys expansion programme. 1 converted factory, 2covered link, 3 air tent, 4 employees parking, 5 site of new
building, 6 visitors parking

issuing of an Industrial Development Certificate meant that planning permission could not arrive on schedule. It took managing director lann Barron some time to convince them that specialist personnel of the type needed by Computer Technology are a raw material, like coal or oil; and that, for reasons connected with the development of the electronics and light engineering industries during and after the war, this "raw material" is mainly to be found around North-west London.

Eventually the IDC arrived but at the cost of a crucial five month delay in the building programme. An immediate solution to the overspill problem had to be found and a temporary building of some kind seemed to be the answer. Foster Associates carried out comparative studies on framed dome structures, contractors huts, portable cabins, and other established temporary building types. To their surprise (and delight) a pure air structure turned out to be cheapest by far. Even on 18 month rental comparison the cheapest alternatives were more than three times as expensive as an air-tent.

With the question of cost settled - Barron estimates that one year's purchase, running and write off costs would still only amount to 1 per sq ft - many other problems still remained to be solved. For a start, all previous air-tents in this country had been used as warehouses or other storage spaces, no one had ever proposed a use as sophisticated as that to which Computer Technology were going to put theirs. Stability, security, acoustic performance, the maintenance of comfort conditions, adequate but not super adequate lighting; in each of these areas the architects, and the company, were moving into the unknown. With imperturbable confidence ("I know we're mad"), land Barron backed Norman Foster to solve all the problems in the ten weeks allocated to bring the project to fruition. Foster and his team did their best - with results which only time can fully evaluate as the cold of winter gives place to the heat and glare of summer.

Heating proved less of a problem than had been expected. Two 500000 BthU oil-fired fan heaters produce a 90(F input to counteract the effects of cold radiation from the skin and maintain an internal temperature equivalent


1, inside the air tent, shortly after inflation. Pvc sheet protecting the Polydrom from the surface of the carpark was later covered by a foam-backed broadloom carpet. The acoustically suspect circulation aisle, 3, bisects the working area; on either side, 2 steel booms carrying fluorescent tubes bounce light off the skin and act as supports in case of envelope collapse.

to 70(F in a traditional building. Lighting and means of escape were ingeniously resolved together by means of a double row of canted steel tubes carrying Fluorescent fittings which double as supports if the envelope should collapse. The lights themselves provide a background illumination of 35 Lumens per sq ft projected upward onto the concave surface of the envelope. A further 40 Lumens sq ft is provided by desk lighting using adjustable lamps. The envelope itself was specified so that it would permit ten per cent of daylight to penetrate, which is equivalent to a further 50 Lumens under overcast conditions. Background lights can be monitored independently to adjust illumination on sunny days, and during the hours of darkness an illumination level of 75 Lumens is available using both background and desk lighting. Solar heat gain through the envelope in the summer is still an unknown quantity but provision for refrigerating fresh air is to be arranged in good time. An interesting aspect of the planning of activities within the Polydrom has been the avoidance of any equipment requiring current at more than 2 Amps. This has made possible great economies in wiring and insulation, one single ring main now encircling the 200 x 40ft enclosure.

The acoustic performance of the Polydrom was another imponderable at the start. Paper thin walls make external noise more of a problem than internal interference - rain for instance roars in a manner familiar only to those with camping or caravanning experience - and the geometrical form of the envelope, unbroken by any excrescence, also causes odd zigzag sound paths. More seriously, it tends to focus noise into the central aisle which serves as a communication corridor between rows of desks separated by banks of rubber plants and simple screens. The architects are confident that planning adjustments will lessen the distractions caused by sound reflection. If they do not, some means of altering the internal shape to break up sound patterns will be tried.

The siting of the building is an example of the enthusiastic ingenuity which has been brought to bear on all aspects of its design. A rectangular tarmac area - which will later serve as a car park- is covered with cherry-red Bennett Buccaneer broadloom carpet, itself coved up onto a concrete perimeter ground beam which anchors the envelope to the ground. The wiring runs around the top of this beam and the twin inlet fans blow over it into baffles which distribute the ventilating and inflating air as well as masking fan noise. After Computer Technology's permanent building is completed, and if its development problems are otherwise solved, the inflatable may be resited on the roof of the new building to serve as a tennis court or general recreation space.

Norman Foster and his colleagues are overwhelmed at the possible applications of their work on air structures: supermarkets, leisure centres, factories and even more sophisticated offices.. He sees an enormous increase in the number of inflatables in use if this project is successful. The difference between 14 shillings per sq ft and four or five pounds (for more traditional unserviced enclosures) is really something to think about after all.


Indirect lighting penetrating the skin, or bounced off it by canted tubular steel booms, is supplemented by clip-on adjustable lamps, 1-4. Three different types of furniture, by Meredew, 3, and Conran, 2 and 4, are being tested against
each other for adoption ,in the new building under construction next:door. At the centre of the whole scheme, 2, is the desk of lann Barron, managing director.



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