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If you want to stop air infiltration into a stud wall and create a superinsulated wall at a fraction of the cost of other methods why not put a poly vapor barrier between the studs and exterior OSB. Insulate between the studs, then apply additional vapor barrier before applying sheetrock. This is all assuming you hit the studs everytime and their are no nails screws etc. penetrating from the OSB or sheetrock into the vapor barriers. In effect you would create something similar to a thermos bottle. No condensation inside their (I am assuming). JMHO, Roger Never assuming anything
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Please abandon all thoughts of ever swinging a hammer.
What you describe is akin to putting food into a plastic bag - it will eventually rot. Your wall assembly cannot dry to either side.
-Rob
*Roger,Moisture will get in one way or another, sooner or later, and when it does, your wall will become one big science project.Steve
*The words "terarium" and "biosphere" come to mind. Lovely self enclosed little enviroments for mass production of mold and bacteria. Bad idea.
*You have done what no one else has ever accomplished...get three guys to agree on a venting/insulating question in Breaktime. Congratulations!
*Hey Teo, you figured out very quickly the reason behind my post. Their was so many opinions on vapor barriers that I thought why not post a really different idea to the mix. Though the recent use of ICF and SIP's in construction is after all making a wall that breaths much less (if any) than standard frame construction. My believe is that the future of construction is in that direction. So the most successful person is one who is able to build a superinsulated durable wall cheaper and faster.
*Rman:Call me crazy, but your idea can work just fine as long as you keep your air cavity (the inside of your thermos bottle)warm enought to keep the water vapour from condensing. This can be accomplished by making sure you have enough insulation outside your second vapour barrier.For example, the Ontario bldg code allows you to place the v.b anywhere in the wall assembly as long as "the inner surface is likely to be warm enough for most of the heating season that no significant accumulation of moisture will occur"They give an example wall section of 1/2" drywall, 2x4 filled with batts,vapour barrier,then insulating sheathing, and this is o.k for a climate similar to mid-northern Canada.The moisture in the air is not necessarily a problem, if it were, all our furniture would rot, right? The problems start when the air containing the water cools to the point where the water vapour condenses and liquid water is allowed to accumulate.That being said, most people still put the v.b on the inside(warm side) of the wall, but If you ever wanted to super-insulate an existing house, you wouldn't have to be worried about removing that old v.b. now.You're a freakin' genius and didn't even know it!!RegardsAndy
*Andy,You assume dry studs to start with. These studs and plates would have been Kiln dryed to at best 19% moisture plus any rain soaked up int the process. Take a scrap od new stud material and seal it in a plastic bag and put it in a warm place for a couple years to test your theory. If you can open it up with out gagging, then rman has something. Until then I like teo's award for bringing out concensus.
*rman... there IS a reason vapor barriers go on the warm side...you have to keep them above the dew point or you create niagra falls within the wall...vent/ no vent & vapor barriers / vapor diffusion is a valid discussion.. but ... come on....you're gonna make me go over there and give rob susz a hug......brrrrrrrrrr
*It seems to me that you could prevent condensation on the barrier material either by keeping it above the dew point, or by preventing the circulation of humid air in contact with the barrier. The big mistake is to allow a space to exist between two barriers. Any moisture trapped between them means all kinds of nasty stuff growing in there.-- J.S.
*All that nasty stuff needs three things to live. MoistureOxygenFoodIt doesn't matter if the moisture is condensed or just hanging out
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If you want to stop air infiltration into a stud wall and create a superinsulated wall at a fraction of the cost of other methods why not put a poly vapor barrier between the studs and exterior OSB. Insulate between the studs, then apply additional vapor barrier before applying sheetrock. This is all assuming you hit the studs everytime and their are no nails screws etc. penetrating from the OSB or sheetrock into the vapor barriers. In effect you would create something similar to a thermos bottle. No condensation inside their (I am assuming). JMHO, Roger Never assuming anything