Well said Jim! In my many years of living reading about something and actually doing it and finding out the results is completely different . You may just have to try a few plants in there when done for a season to see if they survive and thrive. Good luck I always wanted a greenhouse but as one member wrote at first I thought just place it on the ground and start growing the plants. Not so I found out after talking to some local greenhouse owners.

You can double film it and run a blower that causes a wide area between the two layers to insulate in the winter. I realize I'm not using all the proper terms here but greenhouse megastore has videos online on how and why to install it. I'm in 7b and my biggest headache is keeping it cool enough to keep anything alive over the summer. Listen to the advice to do it right from the start, retrofitting is ridiculous! I do dearly love it though! Best of luck!

You are wasting way too much time worrying about the heat. A fast batch of info on your choice of Heat = number 2 oil 140,000 BTU propane 90,000btu. If you have Ngas use it. To heat an area of 150 sq ft from 0 to 70 degrees with a single layer of poly is under 10K BTU. ( maybe a buck a night for heat. All of the stuff about double and triple poly. You will be wasting money and time unless you get it the max and min distance apart. It's very important. Look at Stuff written by OSU, Penn State Cornell & Ohio state for info on greenhouse construction, not The Warehouse you mentioned. They have never grown a plant in their lives. Never add insulation to a greenhouse floor. It will be a MAJOR problem later. Who is this wise ass? I' owned until retirement a greenhouse(78 houses) in Dallas texas that grew 20 MILLION plants each year. I did that for almost 40 years. Supplied All HDepot in the south and all Krogers and WalMarts in the south zone.