There are several advantages to using plastic glazing instead of glass. For example, plastic glass is extremely strong. Plastic glass is also very lightweight.

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You can't shatter plastic glass. Plastic glass will not be chewed on or clawed at by rodents. Plastic glass is capable of standing up to very adverse weather conditions. Plastic glass is translucent to light. Plastic glass will not rot. The best news of all for your plants in the greenhouse; plastic glass will only transfer 40% of the amount of heat, regular glass transfers. This means your plants will stay much cooler, and won't cook as easily in the summer and they will stay much warmer in the winter.

Advantages and Disadvantages

Polyethylene, Vinyl, Renolon, or other types of transparent plastic costs little, depending on thickness. Such plastic is easily attached to the greenhouse framework and all puttying is avoided. It's possible to construct a small 6- by 8-foot free-standing greenhouse for little money providing, of course, that you do all the work.

The modern, improved plastics successfully resist strong winds and heavy snow, and transmit up to 98 per cent of the sun's visible light energy-as much as passes through good glass. Some plastics also transmit up to 80 per cent of the ultraviolet rays, which is greater than through glass.

Two layers of plastic-one inside, one outside of the glazing frame-with an inch of space between them, provide excellent insulation, thus decreasing the cost of heating. Transparent plastic usually deteriorates rapidly and must be replaced every year or two. Certain new plastics being marketed are said to last up to 5 years.

The corrugated types are expensive. However, these have a long life, never need shading, and are not damaged by hail, snow, or such pests as termites. They admit up to 85 per cent of the sun's visible rays. They are not ideal for the real sun-loving crops-annuals, geraniums, cacti, etc.-but fine for orchids, African violets, anthuriums, rex begonias, ferns, and similar plants requiring medium- to low-light intensities.