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  1. #1
    Join Date
    Mar 2014
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    1

    Default Found Styrofoam on home's exterior?

    Hello all,
    We have one bedroom that was always freezing cold as well as the drywall was heavily damaged from the previous owners. We decided to replace the drywall, and at the same time, get to the bottom of the freezing cold situation. FYI, this particular room does have 3 exterior walls.
    So we removed the insulation, intending on sealing all the cracks and then replacing with new, higher value insulation (not much of a jump, what was in there was R-11 and we can only go up to R-13 since it is a 2x4 wall).
    What we were surprised to find was that 70% of the room has just a 3/4 inch piece of styrofoam between the vinyl siding and the room itself. There is only plywood on the corners, about 5 foot in on each side. The rest is all styrofoam. Is this normal to find? The styrofoam is not blue on the one side, it is all white and not very thick. It's really not much stronger than a styrofoam cup, although it is is about 3/4 ... maybe 1 inch thick.

    We are not quite sure how to proceed from here. Is this typical and to code the way it is? Would sealing all the cracks and then putting new insulation help at all where the styrofoam is, or do we need to replace this stuff? Surely our whole house is probably built this way, and we really haven't seen much energy issues other than this one room.

    Any advice/help would be much appreciated!

  2. #2
    Join Date
    Aug 2007
    Posts
    7,239

    Default Re: Found Styrofoam on home's exterior?

    Sounds like a typical vinyl siding install, a layer of foam is added, then the siding installed. I've never seen it applied directly to studs, it has always been over a previous siding material of some sort.

    Vinyl siding, in and of itself, IS NOT a sealed surface, therefore, the way it is installed on your home means that you have massive air flow and heat transfer problems because of it. I would pull the siding, install T1-11 (plywood ) or similar siding, then reinstall the vinyl. I would also include house wrap.

    As for code, not sure if there really are any when it comes to vinyl siding, as it is designed to cover up existing siding (and damage ), it isn't a "structural" component, and therefore, not regulated by the building authority to any degree.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  3. #3
    Join Date
    Jan 2014
    Location
    NH
    Posts
    136

    Default Re: Found Styrofoam on home's exterior?

    Hi, R13 is all you need in the walls if you want to add more insolation then I would add it to the attic and floors. Thanks

  4. #4
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,790

    Default Re: Found Styrofoam on home's exterior?

    The plywood in the corners is for racking support. 1/2" foam was used between the corners on brick sided houses, I was not aware that it was used anywhere else. I have seen OSB with styrofoam on the outside of that used for vinyl siding, but who's to say you can't.

    If you seal the outside of the stud bay, you will have condensation within the stud bay and that will not be good. Fiberglass or any fibrous insulation needs to breath and stay dry or it can lose up to half its efficiency. This occurs at surprisingly low moisture levels.

    The difference between R-11 and R-13 is almost insignificant, it won't really make any difference. If you had properly installed batts, then your problem was elsewhere. I do recommend that when you reinstall the batts, new or otherwise, that you staple the flanges to the sides of the studs instead of the inside faces like most installers do. stapling it to the inside face to create a gap between the fiberglass and the sheetrock is counter productive and leads to a cold wall. Keep the fiberglass as close to the sheetrock as possible and the gap, if any, to the exterior siding. This keeps the fiberglass dry and insulating efficiently.

    You could use foamboard between the sheetrock and the studs to reduce the conduction of heat through the studs, but since you already have foam on the outside, it won't help as much. When you get the job done, your walls will probably still be colder than you like, but if the insulation is done right, it will be a little better.

    You really need to find the real reason for the cold temps in this room. Is the room on a slab that is not insulated? That will cause cold floors and the slab will act as a big heat sink. Is the ceiling insulated and does that insulation go over the joists. Joists sticking above the attic insulation make another heat sink. Is the attic properly vented?

    Do you have enough heat going into the room in the first place? If you don't have enough heat going in, there is not enough insulation to make the room warm no matter how much you add.

    You would be a good candidate for an energy audit. A thermal camera survey would really help you pinpoint the heat losses and save you a lot of money in the long run.

  5. #5
    Join Date
    Aug 2007
    Location
    Maryland
    Posts
    1,716

    Default Re: Found Styrofoam on home's exterior?

    It is somewhat typical to have foam board such as Rmax directly on the studs. The plywood is there as corner bracing to keep the wall from racking. Usually metal strapping is used to brace the wall when using foam board since the insulation value would be decreased at the corners.
    While r11 & r13 may have been adequate in past days, more is often code required now with part of the equation being continuous insulation usually placed on the exterior side.
    Since you have the wall apart I would leave the foam in place, then insulate and drywall.

  6. #6
    Join Date
    Jan 2008
    Posts
    2,203

    Default Re: Found Styrofoam on home's exterior?

    Quote Originally Posted by ed21 View Post
    It is somewhat typical to have foam board such as Rmax directly on the studs. The plywood is there as corner bracing to keep the wall from racking. Usually metal strapping is used to brace the wall when using foam board since the insulation value would be decreased at the corners.
    While r11 & r13 may have been adequate in past days, more is often code required now with part of the equation being continuous insulation usually placed on the exterior side.
    Since you have the wall apart I would leave the foam in place, then insulate and drywall.
    Agreed- but I would also plan on replacing that styrofoam with plywood or OSB at some point in the future. I've seen and built many homes with this combo in the past and AFAIK it's still code-compliant in some places, even with vinyl siding! I won't do this any more as I much prefer the strength of a better sheathing over what little r-value the styrofoam gives. When combined with housewrap you'll probably gain more total energy efficiency than you actually have now too. A relatively easy DIY project when tackled one wall and one sheet at a time

    Phil

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