We used rock wool comfortboard80 to add exterior (continuous) insulation on the exterior walls of our 120 year old home. I spent a lot of time going over the details and perms but ultimately the work itself was easy and the final result more than doubled the Rvalue of the entire wall assembly.
It’s a bit much to explain everything here, but the highlights are:
- Removed the existing cladding (in our case vinyl siding)
- plugged many gaps in sheathing (1x12) with caulk and foam
- Added a vapor-permeable wrap and taped seams
- Extended window and door jambs (made window bucks with lumber)
- Flashed bucks carefully with flex tape
- Installed rockwool in 2x4’ sections (2” single layer - would have doubled up if I had the materials)
- Used vertical furring strips to create a 3/4” air gap*
- Reinstalled vinyl siding -required minimal cutting
Ultimately rockwool won out because of its ability to dry (perm rating) and sound absorption (as important to us for this project as thermal insulation). But many choose to use XPS or ISO rigid foam (be aware those foam options will not allow moisture to pass through, which is a major consideration for older homes without any vapor control layers) Installing an air gap between the insulation and cladding is key for preventing moisture issues, as is properly taping the window and door jamb extensions.
Working with rockwool itself is a dream. It’s easy to cut, easy to fit, is less irritating than fiberglass and has enough ‘form’ to allow installation of furring strips by a single person with just a chalk line.
We will be doing something similar this spring with our “new” (to us) 1940s home, but here the windows need to be entirely replaced (allowing us to do it all together)
Tl;dr - if you are handy enough to be Anne to remove your cladding and replace it, then it’s not any more difficult to add exterior insulation when you do. And if you are going to replace your cladding you should absolutely add a couple inches of exterior insulation.