I’m surprised to hear you say insulation costs where you are make the ROI prohibitive. When I ran the numbers for our place in New England adding insulation was one of the fastest payback periods after sealing leaks. We put over $800 in blown cellulose into our attic but the reduction of energy bills we made that back our first winter.
If I were to add a substantial amount of insulation to the house it would be a major contracting job. The previous owners did it (outer walls + extra in roof of top floor) so I have some. The general rule here is that you only do it if you have to replace the outside wooden panels anyway - as they will have to come off for wall insulation to be added in any meaningful amount. Thus it becomes
very expensive and as electricity is relatively cheap here the ROI is horrible. Something simpler, like adding insulation to the attic would be another story as the work is much less invasive.
The way most houses are built here you can't just blow insulation into the walls. Most houses are built in wood and the outer walls of my house is solid wood so there is no space to blow anything. So the method for adding wall insulation is to take off outer panels, add some say 2x4" to the house to make some space, add insulation in this new space and then refitting outer wall.
This is for old houses like mine (built in the 1930s) Newer houses have much better insulation by default so the marginal effect of bringing insuation up to modern building code will cost a lot but the marginal benefit won't be that great as it's not bad to start with.
For reference I pay around +/- 3000 bucks / year for electricity. This covers heating of the house, hot water, running all stuff obviously and also "fuel" for the electric car. So the budget to play around with for reducing the heating bill isn't that great. And almost half of my electricity use is non-heating anyway based on consumption during the months with no heating. Just the cost of buying new wooden panels + the paint job if outsourced would probably come to like a decade of money spent on electricity for heating with status quo. Even if I did all the work myself, which would be way beyond anything I would take on, the cost of materials alone would be years worth of heating costs. Heck, if I just invested the total cost of such a project the 4% rule would probably cover more than my full heating bill.
In other places with other building styles, cheaper contractors and higher electricity prices the math can obv work out otherwise.
