My house is just decent now. It was built in 1986, so whatever the standard was back then is what’s in the walls. Maybe R13, or lower even. It has older double pane windows, I’m fairly certain they ran out of money when working on the upstairs and tried to do a lot of the finish work themselves. The difference in quality of mud work is significant between upstairs and downstairs. The bathroom up there they cut out part of the wall behind the toilet because they put the drain too close to the wall. So the toilet bowl sat about 1/4 way in the wall lol. And they had to set the toilet on a 2 inch perch so they would have the required grade for the pipe, because they put the toilet on the wrong wall lol. I had to redo that entire bathroom an all the plumbing.Even though you are heating a large area/volume, your climate doesn't get very cold....and it sounds like your place is somewhat efficient.
As for insulation, there was none between the rooms and the attic space that surrounds them upstairs, except some styrofoam that appeared to be from a childrens toy, and only between a few studs. Off one of the rooms is a short walkway to the attic over the garage and there was no blow insulation. Nothing insulating that room from the area over the garage. I could just go on and on. So I’ve been working on it myself. Had blow done in all the spots that needed it. Put up the foam boards on the walls that separate the living space from the attic space upstairs. And i noticed a big difference this winter with my old stove.
But I’m sure all my door seals are lacking, and there must be tons of other places where I’m losing tons of heat. But that seems to be ok. It got down to about 20 last night and I woke up the the house was 74. And quickly went back up to 77. VF is still on the lowest setting. I can’t afford to make the house any tighter or I’ll never be able to run the stove lol. I can’t believe how well it works without having to make any modifications to anything. I was expecting some period where I’d have to maybe tweak it as I figure out how to make it work best for my house but that wasn’t the case.