we built a greenhouse and were able to keep it above freezing in Longmont on all but the coldest/windiest days. it held up to the 100 mph winds just yesterday ( i drove by to see, as we sold the property about 4 months ago.
we used a slope roof kit from here:
https://www.ebay.com/itm/153831758508?hash=item23d1165aac:g:HKMAAOSwWQdfRbZS
1 in electrical conduit. we purchased the kit with the sides and a 10x30 to get an extra frame. cut the horizontal members to 6 feet for extra strength for about 21 x 10 total space covered in heavy duty plastic Agtec Super Strength Clear Woven Greenhouse Film 12mil. we had 12 55 gal plastic drums on the back wall full of water for thermal mass, an inkbird controller for around 1000 watts of heat tape and some box fans. The plants were in hog troughs with old sheets and curtains around the outside and the heat tape under them, the top we covered with a heavy duty row cover fabric like a tiny hoop house. we were able to keep many plants through the winter like snap dragons, bee balm, greens, carrots, herbs, and elephant ears ( yes the tropical zone 10 plant). we also started our tomato's in march with no problems!
we insulated the back wall with 1.5 polyiso with the shiny side into the greenhouse with the Barrels in front of that. depending on how you attach to the ground it would be very easy to move when the time comes.
if you are interested in more details, let me know. it was really not too expensive for such a robust and useful structure. the air temp got below freezing sometimes, but the real thing for plants is the soil temp, and that never got below freezing. I used wireless tags for temp monitoring, but would probably choose another system for that aspect next time.
you have to own the space you have, if you keep saying "can't" you are limiting the amount you learn and grow, both food wise and personally. We knew we would not be in the old place forever and are very grateful for its purpose in our lives. we did invest a lot of money and time, but we got so much out of it that we can appreciate its impact to our lives and move on happy to starting over at a new property.
i have no idea how an 8 year old thread showed up on top of my list. odd. hopefully this info is still welcome.
