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  1. #1
    Join Date
    Nov 2008
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    2

    Default Exterior Wall Assembly

    On a recent show, they talked about the construction of the exterior walls on the Weston house. Does anyone remember how the walls are constructed? I recall there being two layers of insulation and an interior open cell for wiring behind the finished wall. I believe they said the wall achieved R-38. I would like to see a graphic of the wall assembly but could not locate one on the TOH web site. Thanks.

  2. #2
    Join Date
    Oct 2008
    Location
    PacNW
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    6

    Default Re: Exterior Wall Assembly

    I believe they said the wall was an R30. Not sure if that was a peak measurement or an average taking into account the R value of various components and their relative surface area. The wall was constructed to avoid any thermal breaks by offsetting the wooden support pieces in the different layers so there were no sections of wood going directly from interior to exterior. In a typical wall the R value at the studs is probably around R6. But if the studs are covered by 2 inches of foam at R10, then there aren't any direct conduits for cold to leak in. Keep in mind these were seriously thick walls, probably on the order of 8 to 10 inches. They were basically a standard 2x4 wall insulated with foam with a 2-1/2" thick exterior foam and sheathing outer layer and a 2" thick interior air-gap service channel layer. I suppose it would be possible to build similar walls in a conventional house, but there is a big loss of internal square footage when you start to add 4-1/2" on the external walls. And those 2" thick foam boards aren't cheap. Maybe some day they can achieve the same result using recycled packing peanuts. I have seen local houses where a layer of foam was added to the external wall when it was re-sided. They would put on vertical nailing strips and then add probably 3/4" thick foam between and then another layer of OSB/lapboard or T-111. That would kick the wall up probably another R4-5 without adding an unsightly thickness to the structure.

  3. #3
    Join Date
    Oct 2007
    Posts
    175

    Default Re: Exterior Wall Assembly


  4. #4
    Join Date
    Oct 2008
    Posts
    2

    Default Re: Exterior Wall Assembly

    From our web site:
    http://bensonwood.com/work/walls.cfm

    The detailing on the Weston project is a little different from the standard foam-insulated wall described there. The new, R30+ walls haven't been detailed for the web site yet.

  5. #5
    Join Date
    Nov 2008
    Location
    Gloucester MA
    Posts
    1

    Default Re: Exterior Wall Assembly

    What is the "5/8 open matrix"?

  6. #6
    Join Date
    Dec 2007
    Location
    MN
    Posts
    455

    Default Re: Exterior Wall Assembly

    Isn't the matrix a mesh type of material to allow breathability for the exterior siding?

  7. #7
    Join Date
    Nov 2008
    Posts
    1

    Default Re: Exterior Wall Assembly

    check out the wall that is 50% windows. cost effective wall construction???? prefab walls can maybe me justified in really bad climates, but here??? rarely people realize when they pay 150per ft2 and lose 100ft2 to wall size for just r-value, that is 15,000 dollars worth of floor space. that adds about what?120$ per month, your wall r-value will not save you 120$ month!!!!! my idea of the best would be the most cost effective, not the most expensive. these guys must work on cost plus......i do love their show though

  8. #8
    Join Date
    Jan 2008
    Posts
    731

    Default Re: Exterior Wall Assembly

    with heating oil over $3.00 a gal and the size of the house beefing up R value and U value and all the sealing and lapping done with this project can sure save $120 a month and more that's less than 40 gallons of heating oil. Electric for AC ain't cheap in NE either. you think the cost of your carbon footprint is going to go down in future years? I don't.

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