Shonick, have you installed the greenhouse yet? If so it's a lot of work to build footings and foundations under an existing unit. It seems very cost prohibitive and i doubt it will make a big difference. I think the best you could do is make sure there's no air leaks and wrap the GH with film or something that will hold up for the winter. A small electric heater will be costly to run and won't get you to 65 degrees on cold nights but your options are limited.
