Eliminating Moisture In Walls

CharlesD

I thought I'd put this post in this section because I believe it will interest more window and siding guys than any others.
Back in the 70's Arkansas Power presented a seminar on insulation requirements so we could qualify for getting home owners low interest financing for insulation that would include windows and doors, under pinning and in some cases even siding.
One thing I remember the instructor dwelling on for a long time was for the need for proper attic ventilation. He taught that without proper air flow in the attic moisture is not only caught in the attic on the rafters and joists but also in the walls.
Proper ventilation in the attic will draw moisture in the walls up into the attic where it will be dispelled into the air and evaporate.
So, I became a fanatic for proper insulated and vented attics. Also for moisture barriers in crawl spaces.
I found that customers who would vent and insulate their attics properly could eliminate moisture build up on windows and mold on inside walls assuming there weren't leaks in the walls around windows or doors allowing large amounts of moisture to wick in through the sheeting into the wall cavity.
At first on the outside walls we used foiled paper then when Tyvec came out it replaced the paper.
Now I read on here that the only way trapped moisture can be removed from walls is by properly installed Tyvec or black paper (depending on whom you read) and nothing mentioned about proper insulation and ventilation in the attics.
Did things change or have I been wrong all these years? Or maybe different things might work differently in different parts of the county?
I've torn dropped siding off houses that was installed over felt and the felt would crumble. It was usually over 1 x 6 sheeting.

loneframer

I think all the rules change from one climate zone to another. In South Jersey we have a pretty diverse climate. Hot and humid during the summer, sometimes hits 100. Dry and cold in the winter, sometimes below zero. Spring and Autumn can be very wet. I have seen many coastal homes 50 years old or so, stripped of siding and the felt paper was in perfect condition. The only time I've seen it damaged is when a persistant leak fed fungal growth behind the siding. Most insulation installed here is fiberglass batts with Kraft paper facing. I have not seen where this combination has caused a problem with moisture inside the wall cavity, with or without appropriate roof venting. As I said before though, this combination may cause problems in a different climate zone.

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naptown CR

I agree with loneframer. This is not to discount a properly vented attic or crawl space with a vapor barrier on the floor NOT under the joists. The Kraft paper on insulation is a vapor barrier however most installations where the Kraft flange is stapled to the side of the studs defeats the purpose.

If there is no vapor barrier in the attic the moisture will be drawn toward the cooler drier area because the moisture is allowed to move. If I remenber correctly this is called osmosis and is the same principle as having a whole house humidifier in a hallway and evenly humidifying the whole house, The moisture will want to move to where there is less.