W. J. Roberts
The primary purpose of a greenhouse covering is to provide a translucent barrier between two environments. One is normally conducive to plant growth and the other is not. Light energy from the sun passes through the glazing providing energy for the photosynthetic process, converting CO2 and (H2O) to a form of C6H12O6 (carbohydrate) and O2. This amazing process is the basis for all life. The glazing also makes possible the environmental control to allow the photosynthetic process to be carried out at optimum or near optimum conditions. The covering must allow maximum possible light transmission since plant growth in the winter is normally controlled by available light energy from the sun.

There are several coverings or glazings traditionally used for greenhouses. Glass is the original and most reliable from the light transmission standpoint. Other rigid coverings include fiberglass reinforced panels, acrylic and polycarbonate panels, plexiglass and some rigid PVC. Flexible coverings include polyethylene, polyvinylchloride, and tedlar. All of these glazings materials have been used in double or triple glazing schemes to conserve energy required for heating without reducing the available light for growth to inadequate levels.

Roberts, W. J. (1989). GREENHOUSE GLAZINGS. Acta Hortic. 257, 161-168
DOI: 10.17660/ActaHortic.1989.257.19

Acta Horticulturae