2×6 vs 2×4 with strapping, or something else
I don’t know if this should be in Construction Techniques, or Energy, Heating, and Insulation. I went with the first, since it leads to the second.
I have to rebuild the walls on an old house/cottage, around 1200 sq feet. Oddly enough, not quite 8′ tall. In some places the bottom plate is gone, and perhaps the bottom few inches of studs, but not everywhere. The old wall had clapboard siding nailed directly on the studs, no insulation, and homasote + thin paneling on the inside (some really good 50’s vibes). This has worked well for the last 60+ years, but it’s at “end of life”. Location is Gowen MI, climate zone 5, close to 6 (for now).
The plan is to replace the walls, in place. No, knocking it all down and starting over is not on option. Just consider it a new build with restrictions and more labor (putting in a temp wall, replacing the old). The plan is to use modern design: Sheeting + rainscreen, hardiplank, new windows, etc. One constraint is that the current roof overhang is already small, about 6″. I have some decisions to make, and am looking for comments:
Option 1:
Just replace 2×4 walls with 2×4, easy, but not as energy efficient as I would like.
Advantage: Simple, cheap.
Negative: Energy efficiency.
Option 2:
Replace walls that were 2×4 16″ oc with 2×6 24″ oc. Standard sheeting,
Advantage: Energy efficiency.
Negative: Small incremental cost increase, lose 2″ of interior space.
Option 3:
2×4 wall 16″ oc plus 2×3 horizontal strapping. This is the same as option 1, but includes horizontal strapping of 2×3 to reduce thermal bridging, and add 1.5″ of insulation. I don’t know the name for this technique, but I have seen it here over the years.
Advantage: Cost?
Negative: Lose 1.5″ of interior space, not sure what else, perhaps blocking, and placing of outlet boxes? That’s why I am asking.
Option 4:
This one comes from Matt Reisinger. Use a 2×4 wall, but a wider sill plate (or an extension), so I can use Zip-R sheeting.
Advantage: Less thermal bridging. lose less interior space in an already small structure.
Negative: Cost, reduces already small roof overhang, questions about Zip sheeting in general, and shear strength of Zip-R in particular (but probably better than what was already there).
If you are still with me, what are your thoughts? All comments are appreciated.
Replies
Your option 3 looks like the “Mooney Wall” that has plenty of info here in the archives. It or a variation was and is used by a R.I. bldr, Mike Smith. You should still be able to find details here using those names in a search.
Thank you @calvin, that is exactly what I was thinking of. You are right, lot's of information here and elsewhere. I've got some homework to do.
I'd argue the most important thing is good air sealing. I've done the strapping route, it worked well. I firred out the locations for electric boxes to be attached, ran the sheetrock vertical - a bit of a pain, but doable. I was doing an old structure, so I took the time to run a straight edge across the studs and shim the strapping.