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Damp Mold


kurt
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I've got a customer who is paying me to help figure out his mold problem.

Shoe box slab on grade house, but yard drains well. Concrete slab measures "dry". Furnace is fine; combustion gas vents fine. No insulation in sidewalls. Attic insulation & vents marginal. Needs a new roof. Other than that, it's the basic shoebox.

Mold like crazy on the exterior walls from condensation. I said insulate, ventilate, new roof, & install 500+cfm bath fans to exhaust moist bathroom air to the exterior. After that, we'd review conditions for progress. Experimental holes cut in drywall in several locations sez that the siding is working, (empty) wall cavity is dry, no mold.

The bath fans are in, they are working. The insulation guy comes out & says, "no, don't insulate. That will hold the heat in & cause more condensation".

Maybe I'm just tired or bored, but I had no immediate response; I just listened, & said I would post this to the forums I frequent for input.

Mold experts, feel free to guide me. What's gonna happen if they insulate?

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Originally posted by kurt

I've got a customer who is paying me to help figure out his mold problem.

Shoe box slab on grade house, but yard drains well. Concrete slab measures "dry". Furnace is fine; combustion gas vents fine. No insulation in sidewalls. Attic insulation & vents marginal. Needs a new roof. Other than that, it's the basic shoebox.

Mold like crazy on the exterior walls from condensation. I said insulate, ventilate, new roof, & install 500+cfm bath fans to exhaust moist bathroom air to the exterior. After that, we'd review conditions for progress. Experimental holes cut in drywall in several locations sez that the siding is working, (empty) wall cavity is dry, no mold.

The bath fans are in, they are working. The insulation guy comes out & says, "no, don't insulate. That will hold the heat in & cause more condensation".

Maybe I'm just tired or bored, but I had no immediate response; I just listened, & said I would post this to the forums I frequent for input.

Mold experts, feel free to guide me. What's gonna happen if they insulate?

Put a vapor retarder paint on the interior walls and insulate the wall cavity. That will warm the interior surface of the wall, preventing the condensation from occurring.

The moisture is condensing on the wall surface because it's so cold. If you warm it up, you'll eliminate the condensation. But you want the vapor retarder on the wall to keep moisture from moving into the wall cavity and condensing there.

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I agree with Mark.

They can use a PVA (Polyvinyl Acetate) primer to get a very effective one-coat vapor barrier. I'd recommend using cells over any other type of blown-in. Cells itself is a pretty good inhibitor of air movement and is borate treated. So, it not only won't burn, it won't support fungal growth. Sure, it'll settle some over time, but that can be touched up easily and with a good ventilation protocol (good ceiling fans on 24-hour timers with passive thru-wall vents for intake) they'll have less humidity and a warmer, mold-free home.

Oh, wait a minute, I'm opposed to mold testing in any form, so I guess I can't qualify as a mold "expert" and should keep my yap shut. [:-taped]

ONE TEAM - ONE FIGHT!!!

Mike

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Nope, nope, & nope. Sun hits the house all day; no trees. Not surprisingly, the north side gets more condensation & mold, but not excessively more. All the usual suspects check out fine, w/ the exception of insulation & venting.

I really think this is a dew point issue due to lack of insulation.

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Originally posted by Bruce Thomas

Kurt,

Did you mention the dryer venting and kitchen exaust vent for the stove? Are they using a kerosene heater, they add a ton of water vapor to the air.

Bruce

Nope,nope, & nope. Nothing out of line other than no insulation & vents.

I'm mildly competent @ this stuff; I'm a 70's (first energy crisis) veteran & made my chops ala Charlie Wing & "From the Walls In". I asked 'cause I'm paranoid about vapor & mold issues.

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I am assuming that the mold is on the interior side of the exterior walls only?

If that is the case and the interior wall cavities are dry, then it would seem you may have a dew point situation occurring on the interior wall surfaces. This can be exacerbated by high indoor humidity which basically raises the dew point and allows condensation to form at higher temperatures. Since you are in heating climate, I would think that exterior wall insulation would be an absolute must?

The insulation contractor said that adding insulation would “hold the heat in…â€

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