This diy greenhouse was built with pine which is quite a bit less expensive than cedar or treated lumber so you can build it and save. He added an automatic vent to control the temperture and the greenhouse has held up well and since he used 6 mil plastic with is supposed to last for 5 years, you would be able to use your greehouse for at least that long before you have to replace the plastic. Check out the how to on Bepas Garden.
bepasgarden.blogspot.co.uk
