Spraying polyurethane over pink foam board on exterior wall under vinyl siding
Hi everyone
I hope all is well
I own a home built in 1967. I believe I was an old cottage converted to a year round home.
I have managed to bring down the daily air exchanges quite a bit simply By insulting my rim joists with poly.
The vinyl siding was removed I believe, with 2 inches of pink foam board glued to the wooden walls (unsure of type of wood). I believe the board is glued, then there are 2x3s on top of the foam board and the vinyl is attached there.
I want to seal the two sides of the home as they are very leaky. I’m aware that I will need an air exchanger after this Reno as I’ve already made the home quite air tight, based on my energy efficiency score before and after some prior work I did (the house was tested with a fan in the front door). My 2 side walls are very cold. Often times my clothing next to the bed at night is frozen in the.morning (yes I toss my clothes next to.my bed at night lol)
You feel that there is alot of air coming in from above the rim joists and through the wall.
I want to.know if I am safe to spray 2-3 inches of closed cell.poly in between the studs, onto the pink foam board (assuming it is properly strapped). Based on my findings I have : vinyl siding -> studs-> pink foam board -> wood. On the interior I seem to have some kind of thin black tar/rough paper that comes off just with my nail, some super thin old school white foam (kind of like what we find in kids toy boxes) followed by my gyprock. I don’t see a vapor/air barrier, and I don’t know what that tar paper is doing honestly.
I also would like to know if I can put my siding back onto the sruds once the stud gaps are filled (I plan on removing the studs and adding L brackets prior to spraying foam as to avoid thermal bridges) or if I should add 1x3s across the studs to leave an air gap behind the vinyl siding.
Thanks.
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Adding pic of my interior wall. I believe the material behind my gyprock is some kind of MDF.
We need more information.
The most important information we need is your geographical location (or climate zone).
1. You wrote that you have been "insulating my rim joists with poly." I hope you don't mean polyethylene. Do you mean spray polyurethane insulation?
2. You wrote, "I plan on removing the studs." Really? I'm guessing that you plan on removing something else -- but I'm not sure what. (In case you are unsure, studs are vertical framing members, usually 2x4s or 2x6s, spaced either 16 inches apart or 24 inches apart.)
3. You wrote that your layers consist of "vinyl siding - pink foam board - wood." Can you be more specific about the layer you call "wood"? Perhaps you mean 1x6 board sheathing, but it's hard to know what you mean.
-- Martin Holladay
Picture of outside
Side
Hi Martin,
Thanks for going easy on me.
I'm in boibriand Quebec, I believe it's a Zone 1: < 3500 HDDs
You wrote that you have been "insulating my rim joists with poly." I hope you don't mean polyethylene. Do you mean spray polyurethane insulation? A: yes I meant polyurethane, sorry. I put 5-6 inches, whatever code was here (r24)
2. You wrote, "I plan on removing the studs." Really? I'm guessing that you plan on removing something else -- but I'm not sure what. (In case you are unsure, studs are vertical framing members, usually 2x4s or 2x6s, spaced either 16 inches apart or 24 inches apart.) A: they are 2x4 and in some cases 2x3s, vertical. They are holding the foam board and are used for mounting the vinyl siding. They are not supporting anything according to my engineer. They were used to frame/ mount the vinyl siding, and the vinyl is wavy because they didn't use the same size wood...Gonna fix that at the same time.
3. You wrote that your layers consist of "vinyl siding - pink foam board - wood." Can you be more specific about the layer you call "wood"? Perhaps you mean 1x6 board sheathing, but it's hard to know what you mean.
A: I'm not too sure how to explain it...It looks like the wood the frame of the house was made out of... I suppose it's sheathing. not good with terms as you can tell. It seems like solid lumber. Reading on the web, it would be the sheathing indeed. You can't really see it in the image I took...Sorry. I hope that helps boss.
OK, so you're in Montreal (on the way to the airport). I know exactly where you are. You are in Climate Zone 6. Here is a link to a map of Canadian climate zones: Climate Zone Map Including Canada.
The vertical pieces of wood you are talking about are called "furring strips," not studs.
I'm confused about two questions:
1. Why do you want to remove the furring strips?
2. Do you want to install spray foam from the exterior or the interior?
-- Martin Holladay
Martin, I want to leave the pink foam board in place. I want to remove the furring strips, put L brackets to space the strips and avoid thermal bridges. I will then spray PU ontop of the pink foam board...That's the plan at least. So it would be from the exterior.
You don't have much thermal bridging through the furring strips, because you have a continuous layer of 2-inck-thick XPS insulation between the furring strips and your wall sheathing.
I'm not sure how you would attach your proposed L-brackets -- by removing some of the existing pink XPS to expose the wall sheathing? or with long screws through the XPS? -- but the steel brackets won't necessarily be an improvement (since steel is very conductive). Moreover, you can't attach vinyl siding to L-brackets -- so you'll end up needing new furring strips in any case.
If you want to install exterior spray polyurethane foam that is thicker than the existing furring strips, you might want to simply install vertical 1x4s on top of the existing furring strips. Or if you want to get fancy, you can install two layers of 1x4s -- a horizontal layer followed by a vertical layer.
If your wall seems leaky now, don't forget to investigate air leakage paths that won't be addressed by the spray foam -- for example, air leakage between the foundation and the wood framing (hopefully that was eliminated when you insulated the rim joist, but you never know); air leakage around windows and doors; and air leakage at electrical penetrations and plumbing penetrations, if any.
-- Martin Holladay
Thanks Martin
I thought the furring would be a strong bridge...Suppose I'll abandon removing.
Are you OK with spraying the PU on top of the existing foam board
Do you see anything in my wall that would stop it from drying on the inside or cause mold issues by sealing the outside?
Do I need to leave a space between the vinyl and the foam?
I believe I did eliminate all leakage at the foundation when I did the rim joists, best 650$ ever.
Q. "Are you OK with spraying the polyurethane foam on top of the existing foam board?"
A. Sure. That won't cause any problems. (Although installing an environmentally friendly type of rigid foam instead of closed-cell spray foam would be more environmentally responsible.)
Q. "Do you see anything in my wall that would stop it from drying on the inside or cause mold issues by sealing the outside?
A. Not really, although your description of all of the layers is somewhat confusing. You mention "some kind of thin black tar/rough paper that comes off just with my nail" -- that sounds like asphalt felt -- and "some super thin old school white foam" -- that sounds like EPS fanfold insulation (typically installed under vinyl siding). You didn't really tell us where these layers are found. Are they found between the pink XPS and the wood sheathing? Are they found between the wood sheathing and the studs? Or (and this is unlikely but possible) are they found between the studs and the gypsum drywall?
Q. "Do I need to leave a space between the vinyl and the foam?"
A. Ideally, yes. You'll need furring strips to nail the vinyl siding to, as I mentioned, and these furring strips should provide an air space. You can't nail vinyl siding directly to cured closed-cell foam -- for one thing, the cured spray foam will be bumpy.
-- Martin Holladay
Thanks martin.
On the outside is vinyl, furring, pink foam board wood sheathing. In the inside of the wood sheathing it the tar paper, foam, etc. You see I above in my image
Are your stud bays empty, or filled with fiberglass batts?
Thanks Martin.
They are empty. Inside, I don't see anything beyond the white foam board...House is poorly insulated for sure.
If your house has interior asphalt felt and interior EPS foam (along with empty stud bays), it's unusual.
After you remove your siding, you might want to hire an insulation contractor to fill your stud bays with dense-packed cellulose insulation. (The work can be done from the exterior; holes would need to be drilled through the exterior rigid foam and wood sheathing, but these holes can easily be patched.)
Dense-packed cellulose insulation in your stud bays will greatly reduce air infiltration through your wall assembly. If I were you, I would install the cellulose and abandon the idea of installing closed-cell spray foam on the exterior side of your existing XPS.
-- Martin Holladay
Dense packing empty stud bays (3.5lb celluose, or 1.8lb fiberglass, which is sometimes easier in retrofits) will tighten up the house FAR more than spraying the exterior with foam.
Vinyl siding itself is adequately back-vented, and doesn't need the additional vent space of the furring to provide a drying path to the exterior. Spraying open cell foam onto the XPS and trimming it flush to the furring will have nearly the same thermal benefit as of closed cell foam between the furring, and will air-seal as well or better than closed cell foam. It is far greener, using only ~1/4 the polymer, and water rather than HFCs for the blowing agent. Open cell foam would offer quicker drying for the furring for any moisture that found it's way all the way to the XPS layer. In my neighborhood 3.5" of open cell foam costs about the same as 1" of closed cell foam, so it's quite a bit cheaper too.