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  1. #1

    Default house wrap between osb and foam board

    New to this site. Been trying to sort thru the discussions and diagrams related to this topic. Could use some help getting pointed in right direction

    Location: Ohio, 4 miles south of Lake Erie, cold winters, humid summers
    House build in 1982 and now gutted.
    Currently has 2x4 walls, 1/2" osb sheeting, tyvek houswrap.

    Does the house wrap pose any issue when specifically installed between 1/2"osb and foam board? The foam board thickness and type is not yet determined or installed. The concern is trapping moisture where it can't escape. Interior insulation is undecided. If the house wrap doesn't pose a problem, what is my optimum foam board type and thickness and what types of interior insulation will compliment this wall system

    Can anyone point me to a previous discussion or help answer that question.

  2. #2
    Join Date
    Jun 2004
    Location
    Des Moines, Iowa
    Posts
    3,765

    Default Re: house wrap between osb and foam board

    What is going on the exterior of the foam for siding?
    Mark Parlee
    BESI(building envelope science institute) Envelope Inspector
    EDI Certified EIFS Inspector/Moisture Analyst/Quality Control/Building Envelope II
    Level one thermagrapher (Snell Training)
    www.thebuildingconsultant.com
    www.parleebuilders.com
    You build to code, code is the minimum to pass this test. Congratulations your grade is a D-

  3. #3

    Default Re: house wrap between osb and foam board

    Preferably HardiePlank, which I see from other articles that strapping is used when installed over foam board. The next option is a .46 vinyl, which from what I can gather, sounds like strapping may be optional since it has the hollow back. Is there any reason to consider vinyl with foam backing in this application?

    The siding color is to be a dark blue grey

  4. #4

    Default Re: house wrap between osb and foam board

    If I used faced polyiso, will there be an issue between the foil and housewrap. Would I be better off using XPS? If XPS is used, is there a difference using 150 or 250 crush. Or would I be better to rip off all the Tyvek and put up faced polyiso. I cannot find any definitive answers in the articles and blogs I'm reading

  5. #5
    Join Date
    Jun 2004
    Location
    Des Moines, Iowa
    Posts
    3,765

    Default Re: house wrap between osb and foam board

    hardie is heavy so you are limited to 1" foam with fasteners penetrating solid framing 1".

    Vinyl siding is a rainscreen by default and not heavy at all.
    The foam backed does not really add to the insulation value of the assembly despite claims to the contrary. It does add rigidity to the panel.

    I like the xps.
    i would remove the Tyvek and replace it with the Tyvek drain wrap; this will allow any incidental moisture a path to drain. make sure everything is sealed at this plane.
    Next install the foam. what thickness are you thinking of?
    All of the windows and doors will have to be detailed correctly.
    There can be a lot to this process and often it is not done right and the assembly leaks and does not drain.
    What is your experience level?

    This forum in all of its other sections is a pro forum. On this section we do have homeowners post and ask questions and it is tolerated. However we still try not to direct "how to do it" as it can come back to bite us when a do it yourselfer swears they followed all of the advice given and it still failed.
    You do have all sorts of critical issues to address. Do you have anyone locally that "gets it"
    Last edited by Mark Parlee; 02-07-2014 at 06:35 PM.
    Mark Parlee
    BESI(building envelope science institute) Envelope Inspector
    EDI Certified EIFS Inspector/Moisture Analyst/Quality Control/Building Envelope II
    Level one thermagrapher (Snell Training)
    www.thebuildingconsultant.com
    www.parleebuilders.com
    You build to code, code is the minimum to pass this test. Congratulations your grade is a D-

  6. #6
    Join Date
    Jul 2007
    Location
    Toronto, Ontario, Canada
    Posts
    832

    Default Re: house wrap between osb and foam board

    When it comes to using exterior foam sheathing, foam over housewrap over OSB or ply is considered the most durable order of application by Building Science Corp.

    See page 13 here.

    My main concern would not be the ordering of materials but the workmanship details. Many if not most housewrap jobs have some critical error, especially in corners.

    FWIW, I've successfully used Wall Selection 4 in the above guide except that I put brick paper over the foam followed by 1" of airspace and masonry.
    "The fatal flaw of all revolutionaries is that they know how to tear things down but don’t have a f**king clue about how to build anything." Jim Goad

  7. #7

    Default Re: house wrap between osb and foam board

    Thank you for taking the time to provide input to my questions. I am a professional, just not a professional builder. I own and operate a third generation family plumbing and HVAC company. I am remodeling a house to call home for a long time. However, since I am usaully a piece of the building puzzle, I am finding that I thought i knew everything but really know nothing when it comes to remodeling an entire structure focusing on energy conservation. I have used and asked the recources that are available to me, but no one that I can access is familiar with building practices in our area that differs from conventional building practices.

    I will be installing a radiant floor heating system, with a mod-con wall hung, indirect w.h. and buffer tank to accept collected heat from a wood stove heat exchanger and eventually (2) solar panels. I also have a relatively new wood furnace that I'll convert to an ECM motor and duct in an HRV amongst other IAQ stuff in a simple conventional ducted system. But thats the easy stuff for me. My efforts is to reduce my heat loss enough to be able to optimize my radiant design...and minimize the amount of wood I'll have to cut... I initially just planned on furring every outside wall from the inside. Then I stumbled upon the exterior foam concept...I'm finding it hard to find specific installation methods and I'd like to stop finding better ways of doing things after I've already decided on and excecuted a method...hence this site which a fellow HVAC proffesional turned me onto.

    I've read the the 2013 November article JLC posted on the best practices of continuous exterior insulation. I see on a cross section of an older house that has 1x boards for sheeting and lath and plaster that they show housewrap between the boards and the foam, however, on any cross section with modern sheeting it always shows none. I would assume it has to do with the breathability of osb and drywall versus pine board, lath and plaster. I won't mind taking down the houswrap I put up, but my wife definiatly will. Just here looking for some guidance on what steps and decisions I need to make in order to not have to do things twice...like pull off all the housewrap..hahaha

  8. #8
    Join Date
    Jun 2004
    Location
    Des Moines, Iowa
    Posts
    3,765

    Default Re: house wrap between osb and foam board

    Okay
    How about a fist name other the fartspayer.

    When adding to the exterior walls thickness you have to consider how the perimeters of the doors and windows will be handled. If you are replacing all of them then you can move them out as well.

    Are you replacing the windows and doors?

    As worthy said workmanship details are a big part of this assembly.

    OSB for the most part does not have that much "breath-ability"

    As far as taking down the housewrap we aren't' there yet but very close and it would be crazy to leave it just to make your wife happy if it does need to come down.

    Can you post the four elevation views of this home?
    Mark Parlee
    BESI(building envelope science institute) Envelope Inspector
    EDI Certified EIFS Inspector/Moisture Analyst/Quality Control/Building Envelope II
    Level one thermagrapher (Snell Training)
    www.thebuildingconsultant.com
    www.parleebuilders.com
    You build to code, code is the minimum to pass this test. Congratulations your grade is a D-

  9. #9

    Default Re: house wrap between osb and foam board

    Thanks worthy, that link was great and the building science web site was full of info.

    Mark, the house has been gutted, all the doors and windows have been removed. I will snap some photos once the snow recedes a little. The osb cups slightly between studs(16"oc), wouldn't that be enough to provide a drainage plane between the back of the foam and the house wrap, even though its standard house wrap? You can call me Tom

  10. #10
    Join Date
    Jun 2004
    Location
    Des Moines, Iowa
    Posts
    3,765

    Default Re: house wrap between osb and foam board

    Thanks Tom,

    The bowing of the OSB between the studs is not something you can count on. It actually could work against you in that it could become a reservoir to collect and store moisture; the bow would likely straighten back out at the bottom of the wall at the plate line and seal the foam tight to that plane and not allow drainage.

    Pictures would be great. Take them in high resolution. Get elevation shots of all four side and email them to me. You can also post them but you have to compress them down a little; who cares about the snow I can look past that.
    Mark Parlee
    BESI(building envelope science institute) Envelope Inspector
    EDI Certified EIFS Inspector/Moisture Analyst/Quality Control/Building Envelope II
    Level one thermagrapher (Snell Training)
    www.thebuildingconsultant.com
    www.parleebuilders.com
    You build to code, code is the minimum to pass this test. Congratulations your grade is a D-

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