Moisture Problem

Milhaus

I was just out to look at an office space today with an interesting problem. On the inside of the exterior walls, dust is accumulating on the drywall along every steel stud in the wall from floor to ceiling. Wall has block exterior, steel studs, and batt insulation. I requested the original prints to know exactly what materials were used, spacings, air gap between block and sheathing, etc, but for now, this is the only info that I have.

The painting salesman I met with says that this is a moisture problem. Not a mold problem, but a moisture problem. He says moisture is coming through the block, and the difference in temp between the studs and insulation is causing dust to accumulate on the interior at the cold points (along the studs). Similar to condensation I presume.

The block should have been sealed originally, but from the sounds of it, block sealers on average seal only for five years. Customer says they have noticed this problem long before two years ago. Maybe it wasn't sealed originally, hard to tell.

Anyone seen anything like this? Or have a better explanation as to what is happening?

Appreciate the help.

Mark

thom

The drywall itself will be colder along the steel studs. The studs form a heat bridge to the block and outside. The drywall will be warmer along the studs in the summer.

You could be getting condensation on the rock from moisture in the room air, it need not be coming from the block.

Milhaus

I just erased my whole reply. I was ranting anyway.

Check out this article on moisture problems in steel stud assemblies. It's pretty informative and frustrating that we continue to build with practices that cause more problems than their worth. It's written by DOW too, how ironic.

http://www.dow.com/PublishedLiteratu...ge=BasicSearch

Mark

Chris Johnson

As silly as this may sound have you considered that the studs are static charged? Steel is famous for attracting dust - just a thought

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Chris

concretemasonry

Steel studs are notorious for this because they are a "thermal short circuit" due to the conductivity.

For a wall with R19 insulation, steel studs provide and average of R11 to R15 for the wall. Where the studs are, it where the heat/cold is transferred and the cause of the low average. Where the studs are, it is just like no insulation..

Because of the difference in temperarure on the wall, there can be a "shadow" of the stud that attracts dirt because of the temperature difference and possible condesation. - Seen it many times.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Milhaus

Dick -

Any nifty techniques on stopping it from happening? The called us to bid the painting side of it, but I want to explain what is happening and if there are any alternatives. If there is moisture in the wall, I wondered if spray foam would moderate the temp of the steel studs enough to minimize the temp difference?

Mark

armawichita

Steel frame construction is famous for these type of issues. SPF insulation wpuld solve the thermal break in the desogn of this building. Also would need to do a better job of air sealing areas of the wall to stop the stack pressures in the building. Then you would eliminate the moisture problem and potential mold issues you could develope

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