I don’t really know of a way that you can add insulation without taking up interior space, exterior space, or replacing the wall with more modern materials.
- What about the sides of the home not facing the street? Can you add an exterior layer of insulation and then new exterior siding to those walls?
- On the side facing the street, you could replace the stone wall with a different type of wall that was more thermally resistant. This would of course be a major undertaking.
- I am sure you have considered fully insulating the floor and ceiling as best you can.
- If rodents and or insects are a concern, look into Mineral Wool/Rockwool Insulation.
I still use Dia Diagram Editor for most things. I just wish it was still being updated.