Mockturtle, that may be our solution -- I had been resisting the Olympian heaters because of concerns about ventilation and carbon monoxide -- why leave a window open when you want to conserve heat? But we discovered in Utah that we have to leave more room for ventilation than we thought -- we left the vent hood open over our stove (which is an opening about three inches by 12) -- and although we had plenty of oxygen, we had a lot of vapor condensation, which turned to ice on the windows. This despite thick foam insulation on the inside of the windows.
So since we have to provide a lot of vapor ventilation anyway, why not go with a propane catalytic heater? I might also invest in a digital carbon monoxide meter, just to be on the safe side.