This is my second purchase of a Grow T Greenhouse. The first I had for four years and I just needed more space this year for my tomatoes and peppers. I use a small space heater in the spring to add enough warmth at night especially since I "push" my growing season a bit (Zone 7). The four corners at the base and the bottom flaps allow cold, windy days to drop the temperature more than one might like, but on calm days heat loss is minimal. It looks GREAT, is easy to assemble, durable and its affordability has allowed me to add a second to expand my modest growing and selling business. I bought a replacement cover this spring for my old Grow T because I used it pretty hard. Replacement covers are affordable and you can expect 5-6 years from them if you take care of them better than I did,