I love the character of old houses but I don’t love the lack of insulation. There are several ways to add extra insulation to old homes without having to tear down interior walls. My solution is the least expensive and the cutest (in my humble opinion!)
There are companies that will add insulation to walls that are uninsulated by drilling holes on the outside of the house and filling the wall cavities with blown in insulation This doesn’t work all that well since not all the wall cavities get found (thanks to extra framing for windows and such).
Another way to insulate from the outside is to add rigid insulation or batt insulation (there are new types available especially for this purpose) underneath the siding. Of course the siding has to come down first…
Both of these solutions are very effective but costly.