Partial control layer retrofit in CZ 3A
Greetings. I’m a homeowner in zone 3A (Atlanta) with a two-story brick colonial (5-4 and a door). It’s 1970’s 2×4 construction with minimal fiberglass cavity fill in SOME walls, a simple “weather-resistant” fiber-based (non structural) sheathing, and combination brick/siding sheathed (front elevation is all brick, remaining sides are lower-half brick / upper-half siding. There is very little air sealing and no intentional vapor barrier, but the assembly has held up well, aside from being drafty and not very energy efficient.
The siding has reached the end of its lifetime and I plan to replace it. I’d like to improve the wall systems’ performance wherever I open them and would love feedback on the following. From the outside:
– remove existing siding and sheathing (again, non-structural).
– Caulk/foam around all gypsum and framing penetrations (receptacles, wire runs, etc.)
– Fill all exposed wall cavities with mineral wool batts for sound and insulation.
– Sheath areas with zip-system panels and tape/liquid flash to adjacent walls where possible.
– install new siding
I’d love to include a better thermal break in the work, but am concerned about adding too much thickness since the wall planes below (brick) will remain untouched.
Thoughts on the above or better ways to improve the wall assembly while it’s all “open”?
Thanks
Dan
Replies
I would double check the planes. on my house the siding sits pretty far out past the brick parts as it is. another inch would not be too hard to plan.
You could see if access to the wall cavity behind the brick is accessible, and if someone could improve the insulation with blown in insulation of some type.
I would be careful with removing the sheathing, even if fiber based, it might be providing some structural stiffness. would not want to pull it all off and be surprised by a stiff wind. Just want to plan as you go.
Thanks for the thoughts. If an inch or more is possible with the intersection of the planes, what would you recommend? Something like the ZIP-R under my siding? I had been shying away from anything with the insulation on the inside, but as the zip membrane is permeable, the OSB would still be able to dry to the outside and everything on the stud side would still be able to dry to the inside, that might work.
P.S. I planned to expose the wall cavity in sections, not all at once, to you point about secondary structural behavior.
Rigid rockwool is what I would look at. (but would look at the Zip-R as well)
I do not have an informed opinion on all the specifics.
Diagonal let in corner bracing the frame prior to the 70’s could be 1 by wood and after, diagonal metal strap can be found. In your surgery of the existing sheathing you should look to the corners for its existence.
Thanks, Calvin. The house does have let-in diagonal bracing in several other spots that I've seen. Will pay special attention to corner assemblies and ensure shear is not compromised.