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Jed Lukewater 02-11-2009 09:35 AM

2lb. closed-cell insulation over joist mold?
We're considering using 2lb closed-cell spray foam insulation on the ceiling joists of our flat roof.

We haven't opened up the ceiling yet, but we think we may find some mold on the beams when we do.

Are there any dangers to applying spray foam over mold, assuming the beams are sound?

thanks in advance

Ron6519 02-13-2009 05:33 PM

Off the top of my head, it doesn't seem like the brightest solution to the problem. If it were my house, I would clean all the beams and kill the mold. Then insulate.

Jed Lukewater 02-19-2009 09:48 PM

Joist mold
Hey Ron
Thanks for your reply. Yes, cleaning up the mold would be ideal, except that I have read that doing so is easier said than done. Bleach doesn't appear to work. Dry ice blasting would do it, but is expensive. I wondered if by encasing the mold in polyurethane insulation, it might be neutralized. My concern is, that being cellulose, the mold may actually thrive in the 2lb.

jaros bros. 02-20-2009 06:34 AM

It sounds that you have excessive moisture buildup if you think you have mold in the ceiling. You need to deal with this...maybe an air exchanger or dehumidifier. Have you check the humidity in your house. Don't encase wet lumber in insulation because it will just rot as the moisture will have no place to exit. You need to test it with a moisture meter to make sure it is reasonably dry before you spray.

Maintenance 6 02-20-2009 03:41 PM

You need to solve whatever moisture problem is allowing the mold to grow in the first place. Moisture levels would need to be greater than 60% to support the mold, which is beyond what it will take to rot the wood. Depending on the situation, the foam could drive levels even higher. The bleach will definately kill the mold, but any dark stains will be tough to get rid of. Get the moisture under control, bleach to kill the mold, sealer like "kilz" or "Zinsser" to seal the stains, then insulate.

Ron6519 02-21-2009 12:24 PM

"Yes, cleaning up the mold would be ideal, except that I have read that doing so is easier said than done."
That's the way it works sometimes, effort is required to to do the job correctly.
And it's always," easier said then done", whether it's done correctly or not.
The advice given is to guide you away from the path of stupidity, not fling you into it's jaws.

Jed Lukewater 02-24-2009 06:59 AM

OK then .. I will go at the mold with bleach and seal the beams with the anti-fungal as you suggest M6, before insulating.

The moisture buildup I think is caused by a lack of proper flashing at the roof deck level. I should be able to fix that.

Thanks for your response guys

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