Anyone care to comment on the following?
House; 1900, 24 x 22, Gambrel roof, timber sill, walls are full dimension 2″x4″X9′ studs 16″oc, double top plates, studs are also mortised into sill.
project is too reinsulate along with window replacement. After gutting walls to bare studs (16 oc) my plan is to;
1- install let in or kerf in bracing from plates and sills to corner posts, and also from plate to sill in midspan of wall
2-apply 2″ of extruded polystyreene (XPS) directly too studs (from base of sill to underside of roof in eaves
3- apply 1/2 OSB (either basic Advantech or Zip-wall) against XPS, 2×2 solid wood inlieu of XPS at all window openings, along base of sill, and at corners.
4- stud bays will have spray foam (closed cell) applied from interior
my concern is spacing the OSB off the studs, hence the retrofit of wall bracing.
I’d appreciate any feedback or constructive criticsm anyone has
Replies
Good plan- I'd change one thing
I'd cut back the existing sheathing about 4', or to whatever stud is close to that, and replace it with plywood, glued and nailed to the studs, as the wall bracing. Do this on borh sides of all the corners on your house. On a house the age of yours, 3/4" ply should match the thickness of the old sheathing pretty well.
It'll make a stiffer wall, plus will be faster than letting in diagonal bracing.
actually I was planning on removing all the old sheething ,1" +/- pine, and applying XPS directly to outside of studs, hence the reason for all the extra bracing. I'm trying to keep the walls from getting too fortress like and have it hanging way over the foundation.
In a recent FHB article closed cell foam was noted as having the capacity of stiffening a wall structure by 20 to 30 percent.
when you said strip the house to the studs, I thought you meant only on the inside.
Why not leave the sheathing on, spray foam in the stud cavities, and add a layer of rigid foam over that.
And where are you that you need that much insulation?
You might also want to use the advanced search function here, and look for "Mooney wall". Maybe you could adapt that technology to your house.
Hi Shep,
And where are you that you need that much insulation?
Apparently somewhere they started charging for electricity........actually it looks like he's going for a full thermal break as well as insulation.
Pedro the Mule - That'll keep me warmer than my fur
When I re-read my post, I realize I wasn't clear about the rigid foam location. I meant installing it on the interior of the house, as the thermal break, once the walls were insulated.
Then SR could be installed on top of that. For one thing, I think its easier to add window extension jambs on the inside, over trying to build to windows out on the exterior.
BTW, I know you're not the OP, but I replied to you anyway.
windows are getting replaced, they will be applied to OSB, existing ones are wooden single pane with rattly old alum storms.
Also in general buildings "work" better if frameing is inside of insulation envelope (provided moisture is dealt with ptoperly). I realize I could just XPS over existing sheething, but it is uneven thickness, .75 to 1.25, spaces final siding another 1' further from foundation. Also trying not to sheeth studs twice with structural sheething, or puncture XPS with 3.5" nails to apply cedar shingles
If frame can be stiff enough with extra bracing and closed cell foam, it seems that 2" of XPS applied directly to studs and then sheethed with OSB, achieves goals of draft proofing, thermal break, and a minimum of material/$$$
"in general buildings "work" better if frameing is inside of insulation envelope (provided moisture is dealt with ptoperly)"I'll have to mostly disagree with that one. Part of dealing with moisture properly is placing the thermal and VB on the right side of the framing, which in a heating climate is on the interior face.This is already a small house though, and taking away another 2" or so on the inside will drastically reduce living space. 2" of foam will reduce or eliminate dew point, so you might be OK. Maybe noit. Might need other mechanical HVAC controls.If you burn wood for heat, this project will tighten up the house and make it require air source for it and possibly any other combustion heat source.I would change from the EPS ( r5/inch) foam to foil faced polyisoanurate ( r 7/inch)
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my plan is to place XPS on outside of studs, .5'OSB against OSB, and then drainage plane and shingles. Then foam sprayed into stud bays from interior. After everything is done there will be an air/air heat exchanger to manage moisture and air quality.
I've no interest in polyisosianurate, ants love to tunnel thru it, and the composition of polyiso lends itself to tunneling by insects. I've seen it too may times in polyiso, never in XPS thoughExtruded polystyrene is much more difficult for insects to tunnel/burrow in.
I did foam on interior of a house once before, too difficult to get everything tight. placing it against exterior from sill up to underside of roof between rafters makes airsealing much easier.
but this is all beside the point, my original question is will let in or kerf in bracing replace structural rigidity lost by removing pine sheathing
Yes on that Q.XPS will still make a happy home for ants if you are that close to the ground unless you buy it treated with borates. That is not standard and has to be specified when you order it. That also does something the manufacturers don't like - forget whether it is reducing R-value, weakening the board, or shortening its life.
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Would later applying borates to standard XPS also weaken the board and reduce R-values?
I don't know the chemistry of it, but I doubt it.But it might do precious little to repell ants, because a thin sprayed on film that is water solvable would be easy for the ant column to march past.The way Borates work, it destroys them from inside when they eat it.Insects don't 'eat' foam per sae, but the chow down on it as an excavation method to dig the tunnels for their homes. So the borates need to be all thru the material.Spray on borates ( Google Boracare for plenty of info) work OK for wood because it soaks in and migrates further with moisture
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Can you get borate treated XPS?I've only been able to find borates with EPS around here.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
True
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What state are you in? (location)
What interior wall finish are you removing?
Is there any other reason to remove it other than insulation? (wiring? plumbing?)
Jeff
downeast maine, interior finish (mixture of sheetrock covered with layers of paper, fake paneling, fibre board garbage) is basically shot. updating windows and wiring at same time, I doubt if energy (or building materials) will get cheaper in my lifetime, yes I am trying to establish a thermal break
Are you stripping to studs from inside or out or both? Most of your description sounds like exterior work, but then you say spray from interior with foam.
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Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!