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Community and Q&A

Type of insulation to use on outside of house

V9Uo567S5V | Posted in Green Building Techniques on

I will be renovating my house located in kapuskasing Ontario Canada(zone 3/4). The house was built in the early 1950’s with 2×4 construction, the interior of the outside walls have 1/4 ” plywood and drywall applied , no vapor barrier blown cellulose in the wall,tongue and groove boards, then tar paper covered with vinyl siding.
I am replacing the vinyl siding with polymer faux brick panels adding new windows fibreglass windows and doors. I would also want to add about 4 inches of rigid insulationon the exterior of the wall. What would be the best type to add a faced polyiso or something that is much more breathable. Is 4 inches enogh or too much

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  1. jklingel | | #1

    Google REMOTE wall and search here. Your plan is very common. I'm not a pro, but I'll bet you hear foam, water resistant barrier, 1x's for a drainage plane, then siding. Air seal the inside impeccably. I've been told that beyond 4" of foam starts getting tricky to afix the foam properly, without experience. Dunno. I don't think you want any facing on the foam, or you'll have an exterior vapor barrier. EPS breathes a bit better than XPS.

  2. user-939142 | | #2

    might not hurt to add a breathable air barrier on the outside planks before you add the foam on as a secondary backup drainage and air barrier. only a couple hundred bucks. helpful for innie windows too.

    some say if you have a facing on the outside layer of foam, and tape/seal the seems well, that can count as your water resistive barrier; the facing is often not breathable though

    the REMOTE_Manual or any of the Building Sciences papers on high R value assemblies will have plenty of details and graphic examples

    the type of insulation chosen depends on a range of factors, some which may not matter to you, like global warming potential, embodied energy to create the insulation, ability of local contractors/yourself to work with the material effectively, local sourcing, cost, etc

  3. GBA Editor
    Martin Holladay | | #3

    Foam-sheathed walls are designed to dry to the interior, not the exterior, so the permeability of the foam is irrelevant. Once you are up to 4 inches of foam, all types of foam -- EPS, XPS, and polyiso -- have very low vapor permeance, so you won't get any drying to the exterior in any case.

    This type of wall performs very well, so don't worry. Just get your flashing details right to keep wind-driven rain out of your wall system. I'm not familiar with "polymer faux brick panels," but I would be a little wary of the siding type. It is probably worth your while to come up with a detail that allows for a ventilated air gap -- something like HomeSlicker -- between the outside of the foam and the siding.

    You might be interested in this article: Calculating the Minimum Thickness of Rigid Foam Sheathing.

  4. V9Uo567S5V | | #4

    The polymer faux brick panels are produced by Novibric and easyrockcanada.They are made of polpropylene or polyurethane.
    If i were to extend the the insulation to insulate the basement and added the rainscreen would I also have to stop using the rainscreenabove the level where the concrete of the basement meets the wood of the main floor?

  5. GBA Editor
    Martin Holladay | | #5

    Q. "If i were to extend the insulation to insulate the basement and added the rainscreen would I also have to stop using the rainscreen above the level where the concrete of the basement meets the wood of the main floor?"

    A. Yes. You would screen the air intake slots at the bottom of the rainscreen to keep out insects, and you would need to use a different material -- for example, stucco -- to protect the above-grade portion of the exterior foundation insulation.

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