Polyethylene film was selected over glass as the greenhouse membrane for both economic and aesthetic reasons. A major disadvantage of glass is that the weight and small size of the individual panes require a support structure which cuts out as much as 30% of the incoming light and increases the cost substantially. To cover this 1500 sq. ft. greenhouse with a single sheet of polyethylene costs less than $100 whereas it would cost well over $500 if glass were used. The sculptural and asthetic potential of covering 5 to 7 acres of 30° sloping mesa side is obvious.

The major disadvantage of polyethylene is its short life. Even though most films now contain U.V. inhibitors, in a desert climate, ultraviolet radiation quickly weakens the material and when subjected to wind flutter, the membrane can crack or rip after 6 months.

Soleri proposed that the life of a membrane, always kept in tension, thus gaurded against wind flutter, would be greatly lengthened. The membrane is secured on all four sides and held down by 2 cables thus forming four quadrants. Circular adjustable supports are screwed up against the plastic keeping it taut. The membrane undergoes expansion and contraction resulting from diurnal as well as seasonal temperature fluctuations. As the membrane expands during the hotter part of the year, the supports are screwed up; during the cooler periods the supports are screwed down. This system extended the life of a trial membrane from 6 months to 2 years.