Three plastic film materials are in use as greenhouse covers. Polyethylene (PE) film has been used in large quantities for several years. It has high light transmittance, except in the ultraviolet region of the spectrum, and is transparent to infrared or long wave radiation. Its chief disadvantage is its lack of durability—it will last about nine months if put on in October, but may not last until the fall if put on in the spring. There are ultraviolet-inhibited (UVI or
weatherable) PEs that will last longer, but in general they will fail after less than 18 months of exposure.