This is a pic of a really neat greenhouse i saw at the at our home and garden show. It is molded in one piece of a heavy guage fiberglass opaque plastic of some kind. It has a door that seals and two automatic vents at the top. It is almost air tight. very easy to heat. Just thought it is worth sharing.
Greenhouses for sale by Simply Solar Greenhouses
by Alan Hulva
, on Flickr