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            DIY Message Boards  Hop To Forum Categories  Home Improvement  Hop To Forums  General Home Improvement    Insulation; stopping infiltration while allowing permeability
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        Insulation; stopping infiltration while allowing permeability
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        SturdyNail
        posted
        Just when I think I have a plan for how to re-sheath, re-side, and insulate my exterior walls, I read or see something that makes me stop and say "don't do it that way, you'll regret it".

        I was planning on using about 1 to 1.5 inches of rigid foam on the conditioned side of the wall cavity--sealing along the edges with "Great Stuff" (canned, foam, crack filler). This is an approach that some people have recommended to me--including Nestor's response to another of my posted discussions on this forum. Actually, Nestor suggested using 3.5 inch rigid foam, but I plan to fill the remaining 2 to 2.5 inches of the wall cavity with Roxul (I hate working with fiberglass).

        Now I see a very rational, substantiated via video, (and, I might add, entertaining) presentation from Marko Vovk "Mold, The Truth: We have all been scammed" Marko's video leads me to think that the use of foam is a bad idea. I certainly don't want to trap moisture in my walls and cultivate mold.

        So, now I'm thinking;

        • Roxul filling the 3.5" exterior wall cavities (no vapor barrier).
        • 1/2" plywood sheathing
        • Tyvek or Hardi-wrap
        • "Rain-screen" (furring over the wrap to allow drainage & evaporation between the sheathing and cladding).
        • Hardie-Shingle (fiber-cement siding).


        So, where are the errors in my current thinking?
        What is the state of the home renovation art/science with respect to exterior wall construction?

        Thanks in advance.

        This message has been edited. Last edited by: SturdyNail,
         
        Posts: 108 | Location: Western NewYork | Registered: Jan 26, 2012Reply With QuoteReport This Post
        Jaybee
        Picture of Jaybee
        posted Hide Post
        quote:
        Originally posted by SturdyNail:

        So, now I'm thinking;

        • Roxul filling the 3.5" exterior wall cavities (no vapor barrier).
        • 1/2" plywood sheathing
        • Tyvek or Hardi-wrap
        • "Rain-screen" (furring over the wrap to allow drainage & evaporation between the sheathing and cladding).
        • Hardie-Shingle (fiber-cement siding).


        So, where are the errors in my current thinking?
        What is the state of the home renovation art/science with respect to exterior wall construction?

        The above is a good idea. The only unnecessary step is the additional furring to allow drainage. Certainly will not hurt other than if you attach the Hardi to a continuous solid surface there will less chance of any siding bowing.

        A house needs to breath - creating a wall that is sealed from both sides is a bad idea. No wall will be 100% moisture proof so isolating the interior wall from the drying benefits of the house H/A system creates more of a chance for mold to grow, not less.

        Thanks in advance.


        Jaybee
         
        Posts: 9075 | Location: Knoxville, Tennessee | Registered: Sep 27, 2003Reply With QuoteReport This Post
        swschrad
        posted Hide Post
        I gather from the evolution in Mike Holmes' televised recommendations that he's now up for putting the water/humidity barrier at the outside of the wall, in the form of closed cell in-place foamed insulation.

        that's not the direction of code yet, which I see as inside water barrier of 8 mil poly under the wallboard, insulation, sheating outside, then a skin of (cheap)tarpaper or (costlier and more effective) Tyvek housewrap to let moisture out of the wall and block falling rain from entering the wall and house. then your siding.

        siding always has enough of a gap here and there to let vapor out. the exception would be stucco (including fake stone) which is presently recommended to be installed with a false or spacer wall behind it, as you mentioned.

        in either event, there should be a gap at the base of the walls to let any moisture drip out. lack of this is also a big killer among all the plasticized stucco construction of the 90s, which basically results in the walls rotted within 5-10 years in this part of the country.

        This message has been edited. Last edited by: swschrad,


        sig: if this is a new economy, how come they still want my old-fashioned money?
         
        Posts: 4713 | Location: North Burbs, MN | Registered: Mar 14, 2007Reply With QuoteReport This Post
        SturdyNail
        posted Hide Post
        Thanks for your replies Jaybee and swschrard.

        Jaybee, I'm not quite sure what you mean by "isolating the interior wall from the drying benefits of the house H/A system". What are you saying would isolate the interior wall?

        swschrad, you're recommending an "inside water barrier of 8 mil poly". That is one of the things that Marko Vovt (referenced in my first message) "poo pooed". Also, I'm trying to picture the "gap at the base of the walls to let any moisture drip out". Are you talking about the base of the exterior sheathing? That would be nailed into the base/sill plate, so I don't see where there would be a gap. Also, in my case, any gap at the base of the sheathing would be covered with 6 or 8" banding board (probably Azek since my siding is very close to grade).

        Thanks again for your help.
         
        Posts: 108 | Location: Western NewYork | Registered: Jan 26, 2012Reply With QuoteReport This Post
        Jaybee
        Picture of Jaybee
        posted Hide Post
        quote:
        Originally posted by SturdyNail:

        Jaybee, I'm not quite sure what you mean by "isolating the interior wall from the drying benefits of the house H/A system". What are you saying would isolate the interior wall?



        It's the difference between using a barrier that is 100% waterproof (like a layer or plastic) or a VB that can let some moisture / air through (like the paper face of insulation).

        Most houses these days have a H/A system that is running most of the time. Both heat and air will tend to dry out the interior of the house. Over time, this will pull whatever small amount of moisture may be trapped within the drywall and make it dryer. To a lesser degree, the H/A system will also dry the wall cavity on the far side of the drywall. Granted, this is not much, but over years of having a conditioned house interior there will be some drying going on within the walls. However, if there is a solid plastic barrier behind the drywall, then this drying will not happen.

        I don't think you'll find the ONE best method for installing a VB. Things will vary depending on climate, humidity, temperature you keep your house, any outside ventilation, shade, sunshine, windows, interior plants and on and on and on. The one single biggest given is that you cannot create a space that will trap and hold moisture.


        Jaybee
         
        Posts: 9075 | Location: Knoxville, Tennessee | Registered: Sep 27, 2003Reply With QuoteReport This Post
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