Last year I spent a ton heating my fish tank and built low tunnels around my beds to keep plant temps up. This year I'm thinking about heating the greenhouse to around 50-60 and by doing so cut down on the fish tank heating cost. I don't think this would cost any more than heating the tank in freezing greenhouse. I've taken additional steps to insulate the greenhouse and fish tank and have plenty of wood and a backup thermostatic propane heater when needed for when the fire goes out. Any thoughts on this concept?
Solar in my area isn't practical because of lack of sun. The only practical way I've come up with to heat is with wood. You just have to have a source for wood. I'm adapting my wood burner to heat my water right now. When you drop by Mike you can see what I've done and how it works.
My GH sits on a 2x4 base, no foundation. The walls and roof are 2x4 on 24" centers, I could probably go to 36"centers but I feel safer in heavy snowfalls. One thing I like about the wood frame is that I can attach anything anywhere without special hardware. The walls are double layer 6 mil construction plastic. The roof is double layer 6 mil GH plastic for 4-5 years use and less dripping from condensation. I used const. plastic on the roof but it needs to be replaced annually and is more difficult to change than the walls plus I take down the wall plastic in the outside grow season to allow for ventilation but have screen to close off the space. This year I covered all the interior walls with 1" Styrofoam since there's no significant sun to utilize. The FT and GBs are insulated with 1" Styrofoam and there's a top on the FT. The sump is in ground with 2" insulation. I use a wood heater and a propane backup for heat. I light the wood heater in the morning and relight it when I get home in the afternoon and keep it going through the evening. My electric tank heater runs at 18% of what it did last year with this setup.
The humidity is definitely not a problem. I have 2 40 gallon and 1 100 gallon systems in my basement with no humidity issues. Only lights I use are 4 ft. florescent tubes. I have T-12s and T-8s. They work fine for greens and seedlings. I'm still learning the growing part. I understand if you want flowering plants you need different lights. As a starter I would definitely do it and take what you learn to your outside system. Basement is a great place to grow your seedlings for you outside system too. BTW 1 2 bulb 4 ft light will burn about with 32 watt bulbs cost about $2.50 a month. I have 2 over each basement GB. What you'll save not heating outside more than covers basement costs.
If you can get by here I think you'll get all the info you need to start. What I'll show you will prepare you for any "formal " class you take later. If you get your basement system going you'll have lots of questions for the class.