Spray foam covered with vapour barrier? Etc
Recently had some closed cell foam installed on my ceiling (edit, the plywood roof), which I instantly regret. It has been 7 days and it still smells.
Besides that concern, I have a couple insulation questions. I’m in southern Ontario, zone 5 I believe.
1. they spray foamed over the window and door headers and then batted the wall cavities. Then they applied the vapour barrier. I just clued I today that maybe that’s why it smells because it can’t offgas and now it could be stuck in the studs. And aside from that, is it Ok to do double up? Probably only a thin layer though.
2. it’s a slope roof and had no ends built in so they used batts to close the holes and sprayed on those. I was told I can remove them if I want. We were not planning venting the soffits as it’s supposed to be a hot roof. Should we vent in case there is any issues with the spray foam to allow for moisture to dry? Should we keep the batts there?
3. It is a space where one section is not heated and storage and divided by an interior wall to heated space. The entire roof has spray foam and batts on exterior walls with the vapour barrier. VP also on warm side of interior wall. Does this make sense to VP all but the cold side of the interior wall?
this all passed inspection but the more I read the more I question everything.
thanks
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Normally with a "hot roof", the spray foam is applied directly to the underside of the roof sheathing, without any barrier of any kind between -- the spray foam should be ADHERED to the sheathing DIRECTLY. You also say that they spray your ceiling though, so I'm not entirely clear as to how the spray foam was installed here. Usually, if a vapor barrier is required, a suffiently thick layer of spray foam is installed so that a seperate vapor barrier is not required. Adding a sheet of poly in addition to a layer of closed cell spray foam in the same area is probably going to be an issue due to a "double vapor barrier" being present. That could be your problem here.
It's common practice to stuff batts into voids to act as a backing for spray foam. Spray foam needs to be sprayed against something, so you have to block off any areas where you don't want it to go. With a hot roof, this shouldn't be an issue -- you don't have any need for vent channels with a hot roof -- but you do still want the spray foam to cover the top plates of the exterior walls as much as possible.
Note that after 7 days you're still likely to smell the material a little, but the worst of it should have passed. The slightly sweet smell can persist for a month or two, but should be minor, similar to how "new car smell" lasts for a while but eventually fades. The worst stink from spray foam should dissipate over the first few days IF the spray foam was mixed and installed properly AND the installation area was properly ventillated for at least 48 hours or so after spraying. I like to tell customers to do the spray foam work on a Friday, and to go visit someone over the weekend, leaving windows slightly open. This allows for an entire weekend for the worst of the smell to dissipate.
Bill
Thanks Bill for your thoughts. They sprayed the plywood roof, but I said ceiling, so I misspoke.
They did not install a VP under the spray foam for the roof. They installed a vapour barrier over the batt insulation on the walls, which also covered some foam they sprayed over the window and door headers (which I didn't realize they were doing). This would be a thin layer of foam, so I'm curious if it's enough to cause an issue of a double vapour barrier.
A class 1 vapor retarder is not allowed on unvented ceiling assembly.
R806.5.2
Interior Class I vapor retarders are not installed on the ceiling side (attic floor) of the unvented attic assembly or on the ceiling side of the unvented enclosed roof framing assembly.
Sorry, can you elaborate on what this comment relates to? There was no vapour barrier below the spray-foamed roof, just on the walls.
I must have misinterpreted your original post. The same logic that requires this also applies to walls though.
These are the footnotes in relation to wall vapor retarders in r702.7(2)
Class I and II vapor retarders with vapor permeance greater than 1 perm when measured by ASTM E96 water method (Procedure B) shall be allowed on the interior side of any frame wall in all climate zones.
Use of a Class I interior vapor retarder in frame walls with a Class I vapor retarder on the exterior side shall require an approved design.
Where a Class II vapor retarder is used in combination with foam plastic insulating sheathing installed as continuous insulation on the exterior side of frame walls, the continuous insulation shall comply with Table R702.7(4) and the Class II vapor retarder shall have a vapor permeance greater than 1 perm when measured by ASTM E96 water method (Procedure B).
So I guess the question is what do you mean when you say vapor barrier
So the walls were batted and they sprayed a layer of spray foam over the headers of the windows and door (and along thin pockets of framing) and then applied the poly vapour, but over the spray foam as well.
Should I be having them come back to remove the poly vapour barrier from the spray foamed areas and then seal and tape the seams below the batting?
I attached images here for reference, including one before image.
I’m sorry, I misunderstood again, the pictures clear it up. I would not worry about that vapor retarder as those few places with spray foam will communicate and dry with the rest of the assembly. Also the foam in on interior. I wouldn’t worry.
That being said, and maybe it’s in another photo, but there should be blocking at your top plate.
R802.8Lateral support.
Roof framing members and ceiling joists having a depth-to-thickness ratio exceeding 5 to 1 based on nominal dimensions shall be provided with lateral support at points of bearing to prevent rotation. For roof rafters with ceiling joists attached in accordance with Table R602.3(1), the depth-to-thickness ratio for the total assembly shall be determined using the combined thickness of the rafter plus the attached ceiling joist.
The spray foam will help provide this support but really there should be solid blocking there (again, maybe it was added after the fact but seems weird)
Thanks for your comments on the spray foam, that's somewhat encouraging.
Are you referring to the holes where light is coming through? If so, yes, I was surprised as the framer was highly recommended and only does framing. This passed inspection - which I now realize is extremely basic and shouldn't have relied on it to ensure our contractors were doing their job beyond minimum. When I asked about this the inspector said since the joists are heavy they should do their job in helping keep things in position and we are not in a hurricane or tornado-prone area. The fact this was labelled as an 'accessory building' and not an ADU seems to be where a lot of the very basic code requirements are coming from.
The holes were filled with foam batting and that is what the spray foam is adhered to. Technically there is still access on the exterior where the soffits go. Is this worth bringing him back for?
I guess it’s not part of your code, as I work in US. Also realistically the spray foam will be probably just as good or better at resisting overturning so I wouldn’t worry about it, just noticed it looked unusual
I wouldn't rely on spray foam for anything structural, and it's not going to meet code for that. I would put in blocking or a rim/band board for the structural side of things.
Bill
It met the code for the inspection, which is obviously basic. Where does the rim/band board go when it's already constructed?
Freyr-design,
The house is in Southern Ontario. I think you have imported some requirements from the IRC the we don't have in our codes.
I see, it seems pretty strange that they would require mid span blocking but not at top plates, but as you said, different code.
freyr-design,
I meant the vapour-retarder stuff. Our code still doesn't make the distinctions your does and requires an interior vapour-barrier - although that's defined as anything under 1 perm, so in your parlance a class 2 vapour-retarder.
Reading the section on blocking or strapping of the rafters it's unclear to me what's required. It seems to only be concerned with restraining the bottom, not with overturning.
I was told blocking on walls is only required for walls over 14' unless there's a second story. Best practice is another story but it is not code for this build in our area.
That looks like a quality install. No issue there.
The rafters are begging for some more insulation though. I would get the cheapest craft faced batts and staple them up to fill in the gap.
@freyr_design, I don't think that is part of our code (low wind and no seismic issues) as I have never seen it installed.
Thanks Akos. It is supposed to be an R31 and the inspector did a measurement - a few spots only 4.25" (vs 4.5"), but didn't want to bother re-spraying. So there are those batts on the exterior - maybe I keep those there as a wind protection?
I know R31 is code and realistically it is not that bad. The 4.5" of SPF will eventually reach a long term R value of around R25. Add in the thermal bridging of the rafters, you have around an R20 roof. Not terrible but not great.
Assuming those rafters are 2x10, if you fill the space with cheap R19 batts, that brings the roof up to R35 assembly which is much better for not all that much extra cost. Bonus the fluffy helps a bit with noise from the flat roof, despite what many installers think, spray foam doesn't do anything for noise control.
I'll second Akos' recomendation of adding batts to fill the remaining space. I have found that reducing air circulation tends to help avoid moisture problems in roof assemblies like this that use spray foam. Get cheap, low-density batts here that you can squish into the available space, which will vary in depth due to the irregular surface of the spray foam. High density batts are not your friend here, because they won't adjust to the varying depth of the spray foam as well when you stuff them into place.
BTW, I'd allow R6 per inch at best for spray foam. The R7/inch numbers you see quoted are really overly optimistic for performance over time.
Bill
Thanks both of you. Two questions on this:
1. How do i know if it's low density? Would this work?
https://www.rona.ca/en/product/johns-manville-r20-unfaced-fibreglass-batt-insulation-7833-sq-ft-attics-and-floors-90010046-54835728
2. We are installing pot lights and some resilient channel below for the drywall. Is there a minimum space between the bottom of the insulation and a pot light?
Should I jam it really tight against the insulation?
Thanks so much :-)
It's low-ish density. The usual "cheap R19 batt" is 6.25-6.5" thick or so. your link shows R20 in a 6" thick batt, which makes it a little bit higher density, but probably not enough to make a ton of difference. The cheapest R19 batt you find is likely to be the usual low density stuff that you want for this application.
You need IC-AT lights here, which means "Insulation Contact" (it can touch insulation without need of an air space), and "Air Tight" (less air leaky, which means more green, but still leaky). These are very common these days. Note that recessed cans usually aren't the best choice in cathedral ceilings. Puck lights are better. I like lights that can install in the usual 4" round electrical boxes, then I use the white fiberglass "hard boxes" that are easy to air seal, because they don't have any holes (their knockouts are airtight, so you just punch out what you need and don't have to seal anything else).
Bill
Thanks Bill! I can't seem to find any 'cheap' batt that is a bit thicker. The Owens Corning seems to appear fluffier but still says its the same depth. I guess I will just stick to what I can find. The John Mansville is in my wall cavity and it doesn't appear overly structured, so I may just grab that. Thanks again for your expertise.
Don't over think it. Any batts in there will be WAY better than nothing. Even with the sloppiest install, it is still a big improvement over what you have. Your are looking at almost doubling the roof effective R value for not that much cost, this is a great option and about as cheap of an upgrade you can get.
The fluffy might have a hard time staying put. You can use insulation wires or webbing to hold it in place until the resilient channel is installed. Most slim LED lights are insulation contact rated, if in doubt stop the insulation about 3" away from the pot light.