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Hello everyone-
I posted a thread on another site concerning the technique we use to build our homes down here and one person replied stating that we were basically doing too much of a good thing and that we would be causing premature rot. SO…I’d love some input from anyone with some good building science background.
Basically, we frame the house using stnadard techniques, except for our installation of the sheathing. We wrap the house in OSB and after the walls are stood in place, we use white lightening adhesive to seal the perimeter seems of the OSB. Or to clarify, we frame ands stand walls, apply a bead of caulk, then put OSB in place and nail off. Then we wrap the house again in rigid foam insulation (1/2″), staggering the seams between OSB and rigid insulation. We then tape the rigid insulation seams with housewrap tape. As well, after sheetrock installation, we use adhesive caulk to seal all penetrations such as outlets, switches, etc. No vapor barrier is used. We are in the southeast U.S. I’ve talked with a local energy institute and they had no negative comments, but who knows, maybe they are wrong.
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It sounds like where you live you should be putting a vapor barrier on the outside wall. Do you use a foil faced insulation board? If so, the foil face would act as a vapor barrier. If not, its possible for the humid summer air to be entering into the wall cavity, especially if you use air conditioning for log periods of time. The OSB should act as a semi vapor barrier, but maybe in your area it just isn't enough for the temperature difference between indoor and outdoor.
*Sounds like a bad Idea to me, iagree with Jim, and assuming you need some heat in the winter, the warm moist air inside is going to migrate through those walls to the sheathing where it will condense and and rot your walls. You should make the inside walls the tight ones, not the outside. Water vapor that gets into your walls needs a path out, sounds like you're sealing it in.
*I don't think that you should have too much of a problem of condensation in your walls because your temperature differentials are not that great for extended periods. Up north some of us use similar techniques but with a vapor barrier on the inside and there is usually no problem. Building a house too tight can be a problem in another area, that of air quality. Your house should have a minimum number of air changes per hour to maintain its air quality. In an exceptionally tight house a heat exchanger brings in fresh air and expels inside air while preserving the heat. In our houses we generally tell the owners that if they have persistently high levels of humidity, they may have to install such a system. Usually venting the bathroom and the cooking areas is sufficient. Up north you can find out how tight the house is with a blower door test but I don't know if this is available in your area. Good luck.
*Steve, I don't think you are saying the same thing that I am. I feel if he is far enough south and the cooling (air cond.) of the inside of the house is a greater percentage of what he uses, than to me there should be a vapor barrier on the exterior of the home, and using a foil faced insulation board would work if all seam where taped. Check out a book called Builders Guide for Warm Climates by Joseph Lstiburek from the Building Science Corporation, excellent book!!!!.
*Depends where in southeast. We're in NC, which is southeast, but different requirements than lower GA, which is also SE. We have more cooling degree days than heating degree days, but inspectors require vapor barrier on inside.
*Had a house built in the mountains of Washington that was super tight, there were little vents in the closets that were on exterior walls about the size of a cheap smoke detector. The bathroom exhaust fan was on a timer to provide air exchange. You could close the vents in winter, there was still a small amount of air exchange.
*Fresh air is your main concern....You can check moisture yourself over the next few years...I think you will not have inner wall problems...You still need the fresh air though....near the stream,aj
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Hello everyone-
I posted a thread on another site concerning the technique we use to build our homes down here and one person replied stating that we were basically doing too much of a good thing and that we would be causing premature rot. SO...I'd love some input from anyone with some good building science background.
Basically, we frame the house using stnadard techniques, except for our installation of the sheathing. We wrap the house in OSB and after the walls are stood in place, we use white lightening adhesive to seal the perimeter seems of the OSB. Or to clarify, we frame ands stand walls, apply a bead of caulk, then put OSB in place and nail off. Then we wrap the house again in rigid foam insulation (1/2"), staggering the seams between OSB and rigid insulation. We then tape the rigid insulation seams with housewrap tape. As well, after sheetrock installation, we use adhesive caulk to seal all penetrations such as outlets, switches, etc. No vapor barrier is used. We are in the southeast U.S. I've talked with a local energy institute and they had no negative comments, but who knows, maybe they are wrong.