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Wood frame wall details

Peter Abramowicz | Posted in PassivHaus on

Hi
welcome everybody

My question is, how good it will be wall like this:

from inside

1/ drywall
2/ service space for wire (like Swedish houses) -wood frame 2×2 (fill or not with insulation)
3/ vapor barrier (plastic)
4/ 2×6 frame with mineral wool – http://blog.lamidesign.com/2012/01/what-you-don-know-about-mineral-wool.html
5/ OSB 1/2″
6/ 6 -8″ mineral wool
7/ thin coat silicate stucco

I don’t have official data but winter is about 4-5 months with some -5°C to -10°C [23.0°F to 14°F] mostly, but can be -20°C [-4.0°F] for week or two.
Regarding this: http://www.kronoply.com/cms/Specials/Tools/Vapour-Diffusion-Calculator/3338474852.html — It should be OK (I’m not sure if it will be same with mineral wool??)

for inside house moisture I think I want direct air through box fill with perlite , in theory it should absorb moisture
in the future my plan is to use small green house with plant (same as NASA use for air cleaning)
in this way I hope I can reuse some inside air without bringing cold air from outside

any suggestion?

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Peter,
    I'm guessing that you are building in Europe. Your climate sounds similar to the climate in Boston or southern New Hampshire.

    In North America, builders are moving away from interior plastic vapor barriers. Usually all you need is vapor-retarding paint. If you really want an interior membrane, I would use a "smart" vapor retarder with variable vapor permeance instead of polyethylene.

    Are you planning to install exterior stucco directly over your mineral wool? I am not familiar with that method. Or are you planning to install some type of metal lath over the mineral wool to help support the stucco?

    I don't think you can lower the indoor humidity by passing air through perlite. Even if the perlite absorbs some moisture, the moisture remains in the perlite. At some point, the perlite would need to be heated to dry out the perlite, and the moisture from the perlite would need to be collected and removed from the building. That certainly sounds complicated.

  2. Peter Abramowicz | | #2

    It is my mistake, I should say EIFS, so the lath is not needed, only fiberglass mesh over mineral wool. I am not sure if I may go without vent gap, for draining, people from Rockwool, here, said I will be ok. But they don't have so many wood frame houses build as in USA i Canada/
    I like the wall without poly , my first idea was - drywall, 6" mineral wool between studs, OSB or MFP board ( looks like ZIP system wall), 2" wood fiber board, 8" mineral wool, EIFS silicate -in my opinion better as acrylic for drying out.
    I like to remove the OSB , as the is no seismic activity in my area - using drywall and some bracing for shear load. But living in Canada for many years I still have in my head that OSB must be there, and if I have maybe I have problems with moisture from inside, with 50/50 insulation. In IRC they still want vapor barrier inside.
    As for the perlite, it will be in a container (few rows of perlite with the forced air going between , with drain in the bottom.
    regards

  3. GBA Editor
    Martin Holladay | | #3

    Peter,
    I have never heard of an EIFS installation in which the synthetic stucco is installed over mineral wool. Even when EIFS is installed over rigid foam like XPS, the stucco is often damaged on impact -- you see these problems a lot on commercial buildings adjacent to sidewalks. Mineral wool insulation would just make that problem worse. I would check with the EIFS supplier to be sure they approve your details before proceeding.

    Your description of using perlite in a container with drainage holes at the bottom to lower indoor humidiity is news to me. I can't imagine why the perlite would absorb enough moisture from the indoor air to allow liquid water to drain out the bottom of the container. This doesn't appear to follow the laws of physics. Do you have a link to an article on the topic?

  4. Peter Abramowicz | | #4

    Hi Martin

    here you have link
    http://www.paroc.com/solutions-and-products/solutions/walls/thin-rendering
    http://rwiumbracouknew.inforce.dk/media/301658/standard%20detail%20redart.pdf

    and here is the link - hammer test
    http://www.wbdg.org/resources/hp_eifs.php

    regarding perlite - expanded perlite has the ability to hold 200 to 600 percent of its weight in water
    I made some sort of climate chamber with perlite plate (with a few materials I made it more porous and these plates can absorb about 200% of water (of its weight)
    liquid water? - because I integrated perlite plates with wire recuperator

  5. GBA Editor
    Martin Holladay | | #5

    Peter,
    Thanks for the links. I've learned something. I now realize that EIFS can be installed over mineral wool. I'm familiar with U.S. EIFS, and I can assure you that it would never pass the hammer test. Maybe there are stronger formulations of synthetic stucco available in Europe.

    Count me a skeptic on the perlite scheme. I can't see where the liquid comes from.

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