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I’m building a new home and want some opinions about using vapor barriers in homes. My contractor says that he has done it both ways with and without the vapor barrier on your ceilings. There seems to be several schools of thought , some contractors think you trap moisture under your ceilings which I think is probably a humidity problem. We will use blown in fiberglass insulation. Also, is kraftfaced insulation and adequate vapor barrier? We live in Iowa and would like some other opinions if anyone has any… Tom
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Tom,if you think there are several schools of thought on this topic now go over to Energy: Heating,Insulation,&Venting a House on this web site and join the fun.You'll be amazed. Vince
*Tom,what part of Iowa?There is a Tom Nelson in my town,but I don't think he is building a new house.
*Tom. The Kraft paper on fiberglass batts is a "Sometimes" vapor diffusion retarder (VDR)barrier.The permeance--how readily it allows moisture to pass through-depends on the relative humidity. The higher the humidity the more readily it allows moisture to pass through the paper. What is more important than a VDR is the air retarder: the gypsum board covering the ceiling below the attic.Minimise the penetrations of this air retarder, becuase it is mwarm moist air leaking through openings in the ceiling air retarder that causes the trouble. The little moisture that gets through the wall board by diffusion: moisture moving through porous materials, can be "stopped" by painting the ceiling with a vapor diffusion retarder paint. However, Latex paint will do nicely.So before you blow-in cellulose insulation seal the space between the top plates and the gypsum board. Seal all holes in the attic floor. Seal around the stack vent chase.If you have an interior masonry chimney seal around it with a sheet metal collar. Do the same thimg in the basement ceiling. In other words a vapor barrier, as you call it, is worthless if it is punctured with holes and openings which are also in the ceiling gypsum board. Oh yes. Seal between metal case and the gypsum board of the ceiling mounted bathroom exhaust fan. Better still, keep it out of the ceiling, if possible, and mount it in an exterior wall.GeneL.
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I'm building a new home and want some opinions about using vapor barriers in homes. My contractor says that he has done it both ways with and without the vapor barrier on your ceilings. There seems to be several schools of thought , some contractors think you trap moisture under your ceilings which I think is probably a humidity problem. We will use blown in fiberglass insulation. Also, is kraftfaced insulation and adequate vapor barrier? We live in Iowa and would like some other opinions if anyone has any... Tom