I'm looking forward to seeing how this goes for you.
It's way too cold up here in the winter to be able to use my greenhouse all winter without active heating. The amount of heating I would need to use makes it not worth doing.
How deep does the frost go into the ground where you live?
It goes about 2-3 feet deep here depending on the snow cover that we get. The more snow cover we get, the less frost depth.
RE: Greenhouse for winter gardening