Building a GH in a Cold Weather Area

[SaraZ]

I'm in WI and would like to build a greenhouse, and not a little one, something of some size. They are like garages I hear, you can never go too big. My issue is, I am in WI and it gets pretty cold, like frigid freezing cold. We run a outside wood burner for the house and are thinking of pouring a concrete slab for the GH and heating the floor to heat it (like we do our garage), just a thought. What would be the most energy efficient way to go for a gh in my area? Are their any used GH in this area or who is a a good supplier?? I know there are a lot of ya in Michigan and other cold areas and I'm hopeing you can lend me some advice and pointers.

THANKS!