Spotshooter has it dead on. Last year I finished my 8x16 fishhouse. It is insulated with the pink foam. It has a Suburban 20K BTU forced air furnace. Set the thermostate (!) and forget it. No safty worries, and can very confortably fish in sub zero MN winters. I also used a RV "power distribution center" that also has a battery charger built in. Plug in the gen set during the day, and charge the batteries. Runs all night off the batteries. For a lot of information, check out various web sites that deal with building fish houses.
Hope this helps.
dukhntr
