Message Board Thread - "A Drywall Question??"

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A Drywall Question?? Thermal Guy 1/13/2005

I have a question, If there is moisture under three layrers of drywall can a thermal camera see it.

Thank you very much
Thermal Guy
Re:A Drywall Question?? ron lucier 1/13/2005
Naturally an IR camera cannot see through opaque objects like drywall. If there is significant water on the underneath layer and it has an opportunity to evaporate, the lrelease of the latent heat of vaporization causes the water to be below atmospheric (local) temperature. Therfore, it looks cold. Now, place that cold spot behind a couple of insulating layers of drywall, which are probably not in perfect themal contact, and the 6 degrees or so of evaporative cooling becomes very small indeed. Under normal circumstances, at best the wet area will be very diffuse.

However, since water cools as it evaporates, increase the room temperature as much as practical to make the delta T between the lowest "wet" layer and the room. This will give you one way to force the heat transfer to the point where it might be observable.

If you are successful, please upload the images. Good Luck!

Ron Lucier
Re:A Drywall Question?? JKEngineer 1/14/2005
Evaporative cooling is not the only way that sub-surface water can be found. If a heat load is applied to an area that has both wet and dry parts, the wet part will warm up more slowly and look cooler than the dry part. This is the basis for thermal inspections for wet roof insulation. (If done at night, as is usual, the roof is cooling rather than heating and the wet areas look warmer, for the same reason.)

Ron is right that the contact between the layers of drywall are problematic. If you are certain that they are in good contact then your chances are better.

I have recently done several heat transfer analyses of similar systems, including wet areas below dry areas. They were not for sheet rock, so are not worth repeating here for your direct use. If you would like me to do an analysis for your situation, which would address what type and degree of heating to apply, how long to apply it, and how long to wait for the result, I would be glad to discuss it with you. It would give you a leg up on what to do in the field, or even whether to go to the field.

Jack M. Kleinfeld, P.E.
Kleinfeld Technical Services, Inc.
Infrared Thermography, Finite Element Analysis, Process Engineering

4011 Hillman Ave
Bronx, NY 10463

866-884-6644 toll free
212-214-0919 fax and voice mail or
come see what we can do for you:
Re:A Drywall Question?? Thermal Guy 1/27/2005
Thank you very much guys (ron & jack). You have been a great help. Jack I might just take you up on your offer someday. For right now it is okay. Thanks again...

Thermal Guy

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