I believe you may have answered this question in an article but darn I can't find it.
So, need to ask.
I have a new small <800 sq. ft. structure, one story, built to Energy Star 2012 standards in zone 6. Mostly open design.
Building has an insulated crawlspace with rat slab (as of this week the insulators have not come, so exposed studs to work with, but i need to decide).
I plan to use a small wood stove for primary heat (it is piped for outside air intake).
I need a backup heat source for shoulder seasons/ unable to use wood for some illness etc.. I thought a vented propane wall heater without a fan (so a winter power loss wouldn't faze it) would work fine BUT they don't seem to meet the energy star requirements of 80% efficicency. Empire appears to come in around 70% for direct vented . In my state we can not use non-vented propane heaters.
Any advice without going to great expense to meet my needs? I would like to keep it simple and open to rethinking the backup plan, just short on time to make more holes in the envelope.
One propane dealer suggested drilling a hole through the poured foundation to vent a furnace installed in the crawlspace. Others suggested electric type space heater (that won't work during power outages).
All seem puzzled by just how much or...how little heat will be needed to heat this small building.
Seems like the suggestion to go small still has this area to address for help and advise for owners of moderate means. I am retiring this coming year and a suggestion of geothermal is out of my price range plus I would have a difficult time making that cost effective in my remaining years..
thank, and great site!