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  1. #151
    Join Date
    Jun 2004
    Location
    Martinez, California
    Posts
    14,683

    Default Re: Open-Cell Spray Foam & Damp Roof Sheathing

    Quote Originally Posted by Terry
    So Dick are you proposing insulated walls with cellulose and FG should allow for air and moisture intrusion?
    Air intrusion, not moisture intrusion, no cellulose, it does not breathe and is hydrophilic, we want hydrophobic, we don't want wet insulation in our walls. As I've said before on the next home I'm going to violate my 10 year rule since all insulations have failed and try Dow's aerogel insulation, it's got a high R-value for thinner insulation and hydrophobic, and I hope rat-proof, a huge concern here with the hantavirus problem, all insulated tents in Yosemite have been demolished.

    Quote Originally Posted by Yosemite Park
    In the summer of 2012 there were nine cases of HPS associated with a double-wall insulated type of tent cabin called “Signature Tent Cabins” at Curry Village. All 91 Signature Tent Cabins have been demolished and replaced with single-wall traditional tent cabins that have been part of Curry Village since 1899.¹
    BTW, as much as I tried I've apparently got rats in the insulation in home pictured, I'm meeting several people down there tomorrow morning to see what can be done, I can remove the insulation from under the floor but there is no way I can get it our of the walls or cathedral ceilings.


    ¹ http://www.yosemitepark.com/hanta-virus.aspx
    “‎A general State education is a mere contrivance for moulding people to be exactly like one another; and as the mould in which it casts them is that which pleases the dominant power in the government, whether this be a monarch, an aristocracy, or a majority of the existing generation; in proportion as it is efficient and successful, it establishes a despotism over the mind, leading by a natural tendency to one over the body.” ― John Stuart Mill

  2. #152
    Join Date
    Dec 2005
    Location
    Michigan
    Posts
    7,255

    Default Re: Open-Cell Spray Foam & Damp Roof Sheathing

    Quote Originally Posted by Dick Seibert View Post
    Air intrusion, not moisture intrusion, no cellulose, it does not breathe and is hydrophilic, we want hydrophobic, we don't want wet insulation in our walls. As I've said before on the next home I'm going to violate my 10 year rule since all insulations have failed and try Dow's aerogel insulation, it's got a high R-value for thinner insulation and hydrophobic,
    MSDS says it's silica, so far so good. But it only comes in 10mm sheets, you'll need a bunch of layers. How much does this stuff cost?

  3. #153
    Join Date
    Dec 2005
    Location
    Michigan
    Posts
    7,255

    Default Re: Open-Cell Spray Foam & Damp Roof Sheathing

    Quote Originally Posted by Mark Parlee View Post
    dg
    Here is a little info on perms and r value from one of the manufacturers.
    http://www.fomo.com/resources/techni...lvsclosed.aspx

    We get all concerned with ability to dry to both sides of an assembly.
    That link doesn't work for me, but yes, in some climates you may need drying to both sides. It's a valid concern and yes, OSB ain't gonna do it.

    In my climate, winters are very dry so not a concern. A lot of houses need humidifiers, even not so leaky ones.

  4. #154
    Join Date
    Jun 2004
    Location
    Houston & Washington Texas
    Posts
    11,891

    Default Re: Open-Cell Spray Foam & Damp Roof Sheathing

    Quote Originally Posted by Dick Seibert View Post
    You've identified the problem, permeability is no substitute for "breathing", permeability is too slow, you need respiration, air in and air out.
    http://www.greenbuildingadvisor.com/...ry-comfortable

    Response by Martin Holladay,

    I've noticed that people who use the "walls have to breathe" vocabulary often confuse vapor permeability with air leaks -- one more reason why the analogy with respiration is misleading and confusing.
    DG:

    If you want to learn more about perm ratings and sheathing, here are a couple of excellent links from Lsitburek.

    http://www.buildingscience.com/docum...apor-retarders

    http://www.buildingscience.com/docum...some-materials

  5. #155
    Join Date
    Jun 2004
    Location
    Northwest lower MI
    Posts
    370

    Default Re: Open-Cell Spray Foam & Damp Roof Sheathing

    Quote Originally Posted by dgbldr View Post
    That link doesn't work for me, but yes, in some climates you may need drying to both sides. It's a valid concern and yes, OSB ain't gonna do it.

    In my climate, winters are very dry so not a concern. A lot of houses need humidifiers, even not so leaky ones.
    Plywood and OSB act as reservoirs for water vapor. Their permanence increases as the humidity increases, plywood more-so than OSB, probably due to the increased resins used to bind the wood fibers in OSB. The higher the humidity, the more diffusion.
    Attached Files Attached Files

  6. #156
    Join Date
    Jun 2004
    Location
    Houston & Washington Texas
    Posts
    11,891

    Default Re: Open-Cell Spray Foam & Damp Roof Sheathing

    I prefer plywood sheathing over OSB, but I have used OSB sheathing with no problems. And of course Huber's Zip material is OSB. If you are talking prolonged exposure to water, really getting wet, I think plywood is much better than OSB.

    However, in this discussion about houses drying to the inside or outside, I don't using OSB as sheathing is really a huge factor with regards to it getting "wet" by the drying out process. I know OSB perm rating is lower than plywood, but I think most drying of interior air is going to be inward.

  7. #157
    Join Date
    Aug 2013
    Location
    KS
    Posts
    323

    Default Re: Open-Cell Spray Foam & Damp Roof Sheathing

    Quote Originally Posted by Roger P View Post
    Plywood and OSB act as reservoirs for water vapor. Their permanence increases as the humidity increases, plywood more-so than OSB, probably due to the increased resins used to bind the wood fibers in OSB. The higher the humidity, the more diffusion.
    That depends on what OSB is being compared. http://www.huberwood.com/media-center/video/xZ9wy-8_rPc
    Terry

  8. #158
    Join Date
    Jan 2006
    Location
    upstate NY
    Posts
    1,676

    Default Re: Open-Cell Spray Foam & Damp Roof Sheathing

    Quote Originally Posted by dgbldr View Post
    In my climate, winters are very dry so not a concern. A lot of houses need humidifiers, even not so leaky ones.
    Are you talking about Absolute Humidity instead of Relative Humidity? If not, by what measure are your winters "very dry"?

  9. #159
    Join Date
    Aug 2013
    Location
    KS
    Posts
    323

    Default Re: Open-Cell Spray Foam & Damp Roof Sheathing

    Quote Originally Posted by Dick Seibert View Post
    Air intrusion, not moisture intrusion, no cellulose, it does not breathe and is hydrophilic, we want hydrophobic, we don't want wet insulation in our walls. As I've said before on the next home I'm going to violate my 10 year rule since all insulations have failed and try Dow's aerogel insulation, it's got a high R-value for thinner insulation and hydrophobic, and I hope rat-proof, a huge concern here with the hantavirus problem, all insulated tents in Yosemite have been demolished.



    BTW, as much as I tried I've apparently got rats in the insulation in home pictured, I'm meeting several people down there tomorrow morning to see what can be done, I can remove the insulation from under the floor but there is no way I can get it our of the walls or cathedral ceilings.


    ¹ http://www.yosemitepark.com/hanta-virus.aspx
    Perhaps you should follow your 10 year rule until DOW completes MSDS testing, fills in the blanks below and explains water absorption and it's effect on their r-value. Read Martin's blog on misunderstanding 'breathable" same holds true for the terms we find in water intrusion, or diffusion, absorption, hydrophobic, or whatever.....don't get too wrapped up in the fancy words, look at the data, MSDS, on the site from a 3rd party no word of mouth.

    Vapor Density: Not determined.
    Solubility in Water: Not determined.
    pH: Not determined.
    Volatile Content: Not determined.
    Flash Point: Not applicable.
    Autoignition Temperature: Not determined.
    Flammability Limits in Air: Not determined.

    Calling it Hydrophobic may be "stretching the imagination :)

    As far as rats or deer mice hazards looks low, some related to respitory like isocyanates if air born which can happen. Find a rodant proof wall assy.
    Terry

  10. #160
    Join Date
    Dec 2005
    Location
    Michigan
    Posts
    7,255

    Default Re: Open-Cell Spray Foam & Damp Roof Sheathing

    Quote Originally Posted by johnny watt View Post
    Are you talking about Absolute Humidity instead of Relative Humidity? If not, by what measure are your winters "very dry"?
    Yes:)

    There is very little moisture in the outside air (absolute), which results in very low RH inside. Example: house I know, reasonably well sealed but not extremely so, no ceiling cans, etc., 3,000sf, 3 occupants, will go to 25% RH @ 70F right now if they shut off the humidifier.

  11. #161
    Join Date
    Jan 2006
    Location
    upstate NY
    Posts
    1,676

    Default Re: Open-Cell Spray Foam & Damp Roof Sheathing

    Quote Originally Posted by Dick Seibert View Post
    Mark:

    You've identified the problem, permeability is no substitute for "breathing", permeability is too slow, you need respiration, air in and air out.
    Dick, must be everyone agreed with your comment here. What if we forced the breathing? Like, inject a constant metered dose of dry air, or nitrogen...nay argon? As long as we need air exchangers on the indoors, might as well rig some up for the wall assemblies too.

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