A MULTI-BAY INFLATED HOUSE
- to demonstrate that such a structure was cheap and easy to erect, using large sheet film to maximum advantage,
- using a high-tensile steel matrix to stress the structure, to provide crop support, and to minimize structural movement between the bays due to aerodynamic forces and,
- to investigate the problems associated with growing a variety of crops with widely differing environmental requirements. 600 g. (150μ) polyethylene film was used, in rolls 120 ft (40 m) × 36 ft (11 m). Valley gutters were formed by bolting 8 in. × 1½ in. (200 × 38 mm) planks onto 4 in. × 2 in. (100 × 50 mm) posts concreted into the ground at 15 ft (4.6 m) centres. The roof sheeting was battened to this using cord rolled in the film. The walls sloped outwards 20° and consisted of 2 in. × 2 in. (50 × 50 mm) posts at 5 ft (1.5 m) centres, covered with film by battening at the top and bottom, the bottom edge being buried. A polypropylene net of 30 in. (760 mm) mesh covered the roof and was fixed to the valley gutters with hook bolts. 30 in. (760 mm) dia. propeller fans of 9000 ft3 /min (280 m3 /min) were used for ventilation, one per bay, giving a ventilation rate of approx. 2 ft 3 /ft 2 /min (0.6 m3/m2/min). This has been found adequate if the house is damped down hourly.
An inflation pressure of 0.16 in. (4 mm) w.g. is used, which is increased to 0.3 – 0.5 in (8 – 12 mm) in high wind condition. The structure has successfully weathered wind of 36 knots gusting to 45 knots but failure has occurred at windspeeds in excess of this. To achieve greater reliability would require thicker film and a stronger and more expensive structure. A similar structure is being evaluated in Worcestershire. Crops grown successfully include Spring lettuce, self-blanching celery, peppers, aubergines, tomatoes and cucumbers. It is concluded that it is possible to construct large protected cropping areas using air-inflated structures with high-tensile wire stressing. Such structures will withstand average weather conditions but will fail in gale-force winds.
It has been proved that the atmospheric conditions aimed at can be achieved in all temperature and weather conditions, and that crops grow well. An electronic method of linking heating and ventilation to humidity will ensure ideal conditions.