Roofing condensation- black marks on ceiling — wet insulation, wet insulation, close to the master

Roofing condensation- black marks on ceiling - wet insulation, wet insulation, close to the master

Roofing /condensation- black marks on ceiling — wet insulation


Expert: Mark Sundberg — 3/7/2008


A few days ago, I noticed a brown/black mark in the middle of the master bedroom ceiling. When I went in the attic to inspect the situation, I noticed a great deal of condensation around the washroom fan vent (which is extremely close to the master bedroom). It was detached, so I re-attached it. The insulation (fiberglass) was wet and underneath the fiberglass, the wood chips were also wet. I live in an area where we get -40F (max) in winter and +90-100F (max)in summer. The insurance doesn’t cover the replacement of the wet insulation. Do I need to replace it or will it all dry in summer. Are my kids at risk of mold? Is there a product I can use to stop the brown/black marks? What should I do?


Aloha Marc,

I don’t the sound of this at all. However, at least it would appear you have found the source of the moisture. All that humid air, from hit steamy showers to just yourselves breathing have been going up that vent (presumably with fan assist) and the moisture just condensing on whatever was handy, or even just right in mid-air. Hopefully you got the vent tightly sealed, but I suggest you also tape the connection with Duct Tape to be sure, if you haven’t already.

As for the clean-up, I would not leave it to nature. It might dry out, it might not. Not knowing where this is, other than someplace that gets rather cool in the winter and quite warm in the summer, it could be lots of places. The issue isn’t temperature but humidity. Generally winters that cold will be relatively dry as well. But those summer temps could be either dry or muggy. If your summers are dry, you might be OK, but even then I would not risk it.

Now before I go off on my rant on this, let me state clearly that not all fungi, molds and mildews, are dangerous. Most molds and mildews are relatively harmless, but like mushrooms, it’s hard for the layman to determine which are and which aren’t. The ones that are dangerous are rare but the danger they pose is very real and it’s not something you want to take a chance with. Perhaps it’s nothing more than a source of an unsightly stain or blemish and maybe a funny odor. You could probably leave that mess to itself and nothing untoward will happen. Probably. Then again, our children are precious and irreplaceable, so is their good health as is our own good health. Any sensible person would do pretty much anything possible to avoid endangering them or ourselves, even at a significant cost.

Roofing condensation- black marks on ceiling - wet insulation, wet insulation, close to the master

So, yes, you need to take positive action. You need to have the wet insulation removed and the affected area inspected, tested and if necessary, removed and properly disposed of. Even a very dry and hot summer, it may not be enough to dry out the cellulose down deep. In the meanwhile, the fungi that’s there is going to have three or four months to stew and spread and work its way into every nook and cranny. As long as that wet insulation is there, you have a near perfect environment for molds and mildews and the discoloration of the ceiling could well be an indication it has already taken root. Then again, it might just be discoloration from the wet cellulose but I wouldn’t take the chance. I warned you this was going to be a bit of a rant.

Molds and mildews are notoriously difficult to eradicate under the best of conditions. I realize it is not going to be easy or cheap to remove and replace that insulation but it really should be done and it should be done as soon as possible. Although you could probably do at least the removal yourself, I would recommend hiring a contractor that specializes in flooding/leak mitigation and mold removal. They should have the training to identify what they would be dealing with and how to deal with it. They should have the equipment and chemicals to deal with it effectively and safely.

They should remove and properly dispose of all the noticeably wet insulation and any dust or debris plus at least another 12″ beyond where it is wet. Then apply hot air blowers up there to dry the ceiling and framing out. They will have testers to determine the moisture content. Then they can determine if there needs to be further treatment with fungicides. I know this sounds somewhat drastic, but mold really is nothing to fool around with.j

As for the ceiling itself, it’s difficult to say whether or not it should be removed and replaced. If the infestation is not large and you catch it early on, it may not be necessary to remove the ceiling, but only an trained expert with the proper equipment can tell. Myself, I would prefer to error on the side of safety and if I had any doubt at all, I would remove and replace the ceiling. If nothing else, that nasty stain is going to affect the value of your home and will always be a reminder of a potential danger.

All fungi are difficult to eradicate in the best of conditions, in a warm moist attic it can be nearly impossible, especially with a nice source of food to grow on like the cellulose insulation. That insulation is supposed to be treated with antifungals and presumably it is. I simply would not take the chance. If you remove the wet and moist materials and get the rest of the area good and dry and then treat it, you have a good chance of beating it. Good luck.

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