The primary purpose of a greenhouse is to provide protection for your plants and yet allow them to soak up the sun rays at the same time. Because of it’s constant exposure to the sun and other elements greenhouses tend to deteriorate if not constructed of a material that is resistant to ultra violet rays, There are many greenhouses on the market today, including some of the plastic greenhouses, that have uv protection built into them. Always ask the uv level and avoid the ones that have low level protection. Otherwise oxidation will set in and soon you will have only a pile of dust.