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Discussion Starter #1
A customer has some paneling (the thin, cheap stuff) that is warping. I put a moisture meter on it and it's reading in the 20%+ range. The area is about 2' by 2'.

The paneling is on an exterior wall. The insulation above the wall is dry. There is an access panel in the garage. When we opened it, the insulation in the wall was damp, but not wet. To the best of our knowledge, this is the only area in the wall with insulation.

Is is possible for the insulation to absorb airborn moisture and transfer it to the paneling? If so, why wouldn't the paneling also absorb airborn moisture?

Complicating the issue is the fact that there is a small area about 6" by 6" located on the same wall about 6' away that is also warping, though to a much smaller extent. The moisture level is in the 8% range, but I suspect that it's been higher at some point.

Any thoughts on the cause?

Thanks,
Brian Phillips
 

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Yes insulation will hold moisture, even airborne moisture, if it has nowhere to vent.

Fiberglass insulation is intended to hold air. The air is the insulation, the fiberglass is only the media for keeping the air seperated; thus insulating. Warm air holds moisture. Compressed fiberglass insulation won't insulate as wedll as loose fiberglass insulation ebcause the compressed insulation can't hold as much air as the loose.

Panelling is not intended to hold air so it won't really hold as much moisture. The panelling will begin to break apart from the moisture.
 

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Hmm, I'm gonna be a bit more skeptical and guess there is more to this then wicking moisture out of the air here. I suspect there is more going on. I would look for more signs of water either standing and being wicked up the insullation or coming in from some other source. It may be happening only on a temporary bases and taking months for the moisture to wick out of the insulation to the level that you are finding now. Where you find something that wet there is usually a water source somewhere.
 

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Discussion Starter #4
I looked everywhere for evidence of standing water or water intrusion. The attic was dry as a bone. No water pipes in the wall or anywhere nearby.

I put a moisture meter on the drywall in the garage. On the wall with the problem the reading was in the 12% to 14% range. On other walls it was around 2% to 4%.

If the problem was limited to the area where the insulation was, I'd be pretty convinced that's the problem. But as I said there is a small area 6' away doing something similar and there's no insulation there.

Is it possible for the airborn moisture to form condensate on wood? The inside of the house is cool, and the air on the other side the paneling is warm and moist. I realize wood is a pretty good insulator, but the paneling is the thin stuff.

The house is about 70 years old and this has never happened before (to the knowledge of the current owner).

BTW, this started out with him blaming us for the problem. We painted his interior 2 years ago and he was claiming that the paint was peeling. I cut away a section of paint (including prior coats) and showed him the mildew on the paneling, as well as the rotting paneling. He changed his tune and I'll be submitting a bid for repairs next week. But I want to solve the real problem, if possible.

Brian Phillips
 

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Brian said:
Is it possible for the airborn moisture to form condensate on wood? The inside of the house is cool, and the air on the other side the paneling is warm and moist. I realize wood is a pretty good insulator, but the paneling is the thin stuff.
Asked an answered.

Insulation will sponge moisture and without proper ventilation will retain that moisture.

I'm not sure abotu wall framing but in roof framing, if you decide to insulate between the rafters you must leave a space at the bottom of the roof deck and top of the insulation or you are guaranteed mold. This is because the insulation sponges moisture and holds it there against the wood. The lack of air flow prevents the moisture from dispersing. I don't see why this would be any different in a wall.

We are talking about an exterior wall with this thin panneling? Is the panelling rated for exterior application and was it installed properly with a flashing where each panel meets. Also was a tyvek or similiar house wrap used behind the panelling to water proof?
 
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