I'm planning a 20x20' detached garage which will have a bonus room built into the roof trusses. I'd like to use this bonus room as my home office — so, since I live in the cold North, it'll need a heat source.
Given that the space will be thoroughly insulated, and that the only mechanical I can easily run from the house is electricity, how can I heat this space (12x20x7', just shy of 1700 cubic feet) in a reasonably efficient manner?
- As it'll be used mostly during normal business hours, the temp can be allowed to dip at night, but must stay reliably above, say, 50° (for the sake of the computer equipment)
- The faces of the gable roof are East and West (I'm open to insulated skylights and/or some kind of passive solar, if it'd help)
- If needed, I can run water lines to the space (the detached garage will only be about 12' away from the house)
- I'm open to some sort of burned fuel (pellet stove?), as long as the fuel itself is relatively inexpensive and widely available (I have access to as much chopped wood as I can burn, but something more compactly stored / consistently burned would be nice)
- The trusses will be customized anyway, so I can use a heavy / reinforced bottom web, should it be necessary to pour some kind of underlayment layer (for in-floor radiant heating or just plain heat retention via mass)
- The furnace for my home is fueled by our city's gas lines (may be possible to run a line to the office space, if needed)
Given all of this, what kind of heat source (or combination of sources) would get this home office through a cold Wisconsin winter in a reasonably efficient way (up-front cost can be higher, assuming the savings make up for it in less than, say, 5-7 years).
Edit: change text in last paragraph from "as efficiently as possible" to "in a reasonably efficient way", to clarify the scope of response I'm looking for.