1899 house, no sheathing, insulating from exterior
I’m Rob. I’m in WV (Climate zone 4/5). My 1899 has no sheathing, true 2×4 studs, poplar dutch lap siding. I’m trying to balance energy efficiency, cost consciousness, with historic preservation. Because the original siding must be removed for some repair/replacement, I’m tackling the project from the outside. (Original wall and ceiling beadboard makes insulation from the interior unworkable.) I have several original double hung windows that will stay so I prefer to find a way to limit my challenges around windows by adding several layers. I also prefer to avoid spray foam on the original structural timbers in the interest of future restoration. If it’s the absolute best option in my situation I’d consider spray foam if I can protect at least the backside of the wall beadboard.
Is it possible for me to put mineral wool matts (Rockwool) into the stud cavity, use a quality weather vapor barrier and then reapply siding? Will I need to use fir strips or other form of air gap. I’m hoping to avoid adding sheathing or at least minimalize the impact that adding space to the exterior wall will have around my windows.
Thanks for the guidance. I’ve seen lots of advice of tackling this scenario from the interior. From the exterior, I’m hoping to gain energy efficiency while also limiting the “build out” of the exterior wall. It’s asking a lot, I’m sure. What ideas do you have?
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Check out articles such as this: https://www.greenbuildingadvisor.com/article/the-high-cost-of-deep-energy-retrofits
There are things you could do that might be outside your budget—or not. If the siding has to come off, it would make sense to install plywood sheathing and tape the seams to establish an air barrier. If it were my house, I’d remove the windows and treat the openings to prevent water issues. Similarly, I’d consider installing reclaimed rigid foam over the sheathing as well. 1x strapping or Cora Vent would be worthwhile for the air gap/rain screen. High density batts in the walls (installed before the sheathing) would be an absolute requirement.
Really, there is so much you could do on a project like this. Sequencing projects and not making changes that are likely to create future issues is paramount. So have a plan, and ask for lots of advice on GBA (like you’re doing now). :-)