idea 1) Add a single zone minisplit that directly feeds 3 rooms with only 1-zone via tiny duct runs. Mitsubishi and Fujitsu both have these. I think the indoor unit might fit in the ceiling of a closet and losing 8 inches might be acceptable? The idea being that we could then turn off the “central heat” completely on cold nights and during the day. $2000?
idea 2) Much cheaper — thicker down comforters, sweaters, fleece, hat, my 100W electric panel under-desk (vs 1500W space heaters) with blanket for a sort of “homemade Kotatsu”. The problem is that fingers still get cold and it’s more flexible and more comfortable to not bundle.
idea 3) Some combo of the above.
idea 4) pellet stove or wood stove. Problem being that it would be mainly heating the big common space so getting heat to the office/bedrooms would be tricky.
**Main goals are: 1) save $ and 2) KISS (Keep it simple, stupid) and 3) reduce carbon