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Attic mold/mildew


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I have recently developed a mold or mildew problem (not sure exactly which one or how to tell) on the underside of the roof sheathing but only on the north facing side this 2 story home. The sheathing exhibits black areas/spots and there is a musty smell evident within the attic. The house was built in 2002 and has soffit and ridge vents although when the contractor installed insulation he covered the soffit vents with insulation and installed blue baffels between the rafters. The baffels begin at the soffit and extend about three or four feet up the roof line. I am assuming that the baffles are not allowing proper ventilation and that I should remove the insulation from above the soffit?? All fans are vented through the attic to the roof. I do believe that the cold winter coupled with an extended period of snow on the roof and the lack of adequate ventilation is causing condensation. Comments on the use of baffels and their adequacy and also what to do about the mold/mildew on the sheathing would be greatly appreciated. I have searched the forums and have found many varying opinions on what to do and whether or not to apply Boracare or similar or to just correct the ventilation problem and leave alone. I can provide pictures if needed. Thank you in advance for your time and help!

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Usually cold winter air does not carry much moisture, but maybe under certain conditions, it's possible, like a fine mist blowing in. No doubt the roof sheathing is cold enough to cause condensation of moisture from the attic air.

I would look for leakage from the living space such as around the hatch or potlights, ceiling fixtures, etc. That air carries moisture which can condense on the cold sheathing. There are general rules, but a lot of variables. It's not an exact science.

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The furnace does not have a humidifier nor are any portable humidifiers are used. The bathroom fans are both vented above the roof line and the vent hoses seems to be securely attached and without any major leaks. I will investigate for any small leaks. The strange thing is that the bathrooms are located towards the east end on the north facing side and the black spots/areas seem to be most prevalant towards the west end of the north facing side. I would expect the problem to be the worse above the bathrooms. No black areas/spots are evident on the south facing side. I will post pics later when I get a moment. FYI, The ceiling has R-38 insulation with baffles installed. - Thanks, Cory

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A musty smell in an attic is a pretty sure sign that ventilation isn't happening as it should.

If I understand your post, the baffles that were installed may not successfully overcome soffit vents blocked by fiberglass batt insulation. When I see insulation installed like this, I always call for it to be pulled back to insulate the interior wall and ceiling surfaces only. Not only can insulated soffits cause humidity problems, but it's a player in ice damming as well.

The first three things to do: 1. get the insulation completely out of the soffits. 2. make certain that your attic access door, scuttle or folding stairs are well sealed when shut, to prevent heat and humidity from the interior to find its way to the attic, where it will condensate on the slopes that see the least sun. 3. make certain that you actually have functional ridge vents. More than once I've found tar paper under the ridge vent, which a quick glance will easily pass off as the typical black fiber (filter) that should be there. For this reason, it has become automatic for me to scrutinize the underside of ridge vents.

Hope that helps.

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If you have baffles installed, how is the insulation "in" the soffits? Don't the baffles start at the soffit itself? The baffles are meant to isolate the edge of the roof line so the soffit can't get blocked. Or were they installed in reverse order...

Mabye I misunderstand you...

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I'm not sure what you mean when you say he "covered the soffit vents with insulation." Do you mean to say that the soffits have insulation in them or are you referring to how baffles were installed between the rafter bays that extend into the soffits and then insulation was placed against the baffles?

Michael's comment about the ridge vent and felt is a good possibility. If that system is working right, you should be able to feel the air movement as soon as you open the hatch. If you can't something is impeding air movement. Baffles won't be the issue unless they've been collapsed, which is often the case here. Sometimes the insulation guys place the insulation so tightly against them that the bottom of the baffle is bent inward and only a little bit of air can come up through the edges of the baffles. Do you have a basement or a crawlspace? If a crawlspace, do you have a tight-fitting vapor barrier capping the soil? If a basement, is there anything down there that will be pumping large amounts of moisture into the home? Do you cook with a gas stove? If so, is there an exhaust fan over the stove and do you use it?

You've got to seal all air passages around recessed lights, where wires and pipes come up through wall plates, around chimneys, around hatches, etc. Once you've got the ventilation working right, then you'll need to nuke the spore with something to kill it.

Killing it is only half the battle if you intend to sell in the future, because if you just kill it and leave the dead colonies there you'll be haunted by the stuff when you go to sell and some anal retentive home inspector goes up in there, finds it and writes it up.

With spore you're kind of screwed if you leave it in place. If you use BoraCare or some other clear treatment the stuff will still be evident; if you use Concrobium or some other cover up type treatment the roof is going to say, "Look at me, I had a mold problem," and it will look like you tried to cover it up. That leaves getting the underside of the roof cleaned and then treating everything so that the spore can't come back - treating is where BoraCare can shine but it's no good for removal.

Cleaning the underside of that roof is going to be a royal pain in the.....

ONE TEAM - ONE FIGHT!!!

Mike

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With spore you're kind of screwed if you leave it in place. If you use BoraCare or some other clear treatment the stuff will still be evident; if you use Concrobium or some other cover up type treatment the roof is going to say, "Look at me, I had a mold problem," and it will look like you tried to cover it up. That leaves getting the underside of the roof cleaned and then treating everything so that the spore can't come back - treating is where BoraCare can shine but it's no good for removal.

Mike, I have never seen Concrobium that is not clear. I agree with everything else in your post. Not real crazy about Boracare

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Hi Les,

I don't know much about Concrobium except that the last time I did a home where a "professional remediator" was supposed to have done the work, the underside of the roof had been coated with something that looked suspiciously like Kilz, which isn't supposed to be used over mold and mildew. When I pointed that out to the client, they showed me the remediator's documentation and Concrobium had allegedly been used to seal the roof; that's why I made the remark, "Hey look at me...etc."

ONE TEAM - ONE FIGHT!!!

Mike

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here are some pictures to follow up with my original post. I greatly appreciate the information.

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tn_2010222121049_baffles%20at%20soffit.jpg

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tn_2010222121140_insulation%20removed%20from%20soffit.jpg

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tn_2010222121222_soffit%20vent.jpg

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tn_2010222121244_soffit%20vent2.jpg

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Read Kibbels post a couple back, and Kogels post where his last sentence says "It's not an exact science".

This is less about insulation and ventilation and more about "where's all the water coming from that's causing the problem?".

And air sealing.

If one reads the history of how we got to where we are with insulation and ventilation, one understands that none of the current code requirements are based in much good science, and more in trying to figure out conflicting and contradictory issues relating to building construction techniques.

Figure out how all that moisture laden air is getting into the attic, fix it, then worry about removing the mold.

Personally, I'd figure out the moisture part, and I'd leave the "dead" mold right where it's at, and figure it out how to get rid of it when I eventually tried to sell the house.

Yeah, I'm a Philistine......

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