I have a fiberglass greenhouse 10' x 12', it has 4 roof vent windows. My DH put some cylinders on 2 of them that open and close according to heat conditions. I store plants in the winter in there and start seeds in the spring. With the high temps we have in Mississippi in the summer- growing anything in there then is out of the question. This is the 3rd year we have had the greenhouse and I just love having it. The first year I stored plants - several people asked me to store plants for them in the winter which I really didn't mind until I was the only one around at watering time. Contrary to what some people believe-plants DO need water in the winter!! Now I only store my plants- sounds selfish, right? All that time I spent wintering everybody elses plants could have been spent quilting!!