The Inner Cover of a Tunnel Greenhouse is supported by the Inner Hoop? members and forms, together with the Outer Cover? a Cavity Space system that can filled with Liquid Bubble Insulation at night and/or the bubbles can be used also during the day for Bubble Shading. The Inner Cover helps to contain the bubbles and form a sealed building envelope.
The Inner Cover also supports the Liquid Film, which is formed by the Soap Solution when it is distributed over this transparent inner layer of the Sola Roof. The slight negative pressure in the Cavity Space controls the surface smoothness of this material, which is most often a transparent Poly Film?.
Poly Film? can be used for this component because there are not any significant loads placed on this layer of the Sola Roof. The Outer Cover? takes all the snow and wind loads and therefore requires more physical strength. The Inner Cover requires anit-drip properties for the surface showing to the interior. This is due to the significant flow of condensation down the surface to a condensation collector at the lowest edge where the sheet material continuously attaches to the Side Wall? frame at the Growing Bench. This condensation is recovered from water supplied to the plants for growing and used by the plants for cooling by the process of Plant Transpiraton?.
The Inner Cover is typically a flexible sheet material like Poly Film? which has a sufficient width to reach from the ridge of the Tunnel Greenhouse frame to the Side Wall? and End Wall? structures, with the length of the material extending in a long, continuous run from End Wall? to End Wall?. Along the top edge the Inner Cover continuously attaches to the Bottom Chord? of the Roof Truss? that forms the ridge structure of the Tunnel Greenhouse.