Mold in attic


Old 04-06-11, 05:49 PM
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Mold in attic

I have a single story home with basement. I replaced our roof including the sheeting 2 years ago due to mold and dryrot. The attic was not properly ventilated so I added a ridge vent and vented soffit. Shortly after that, I noticed there was mold under our attic floor. I thought this was also caused by the ventilation problems. I replaced all the insulation due to the fact it was wet and moldy. I installed Kraftfaced insulation with it facing down to the living space and put down OSB floor. It has been 1 year since I installed this. During remodeling I discovered mold growing on some of my roof sheating and under the attic floor again. There is only 6 inches of insulation in my attic, 2X6 ceiling joists, so my floor is touching the insulation. I really need the storage space since my home is small.
I also have an attic fan installed in the gable end. I have read lots about not having a fan with ridge vent. Not sure if that matters much or not.
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Old 04-07-11, 05:03 AM
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Is there a complete vapor barrier seal under your insulation. In winter, warm moist air from inside can meet cold and that can cause condensation if there is air flow. The insulation is only a thermal barrier and not a complete thermal break for one thing, and the ceiling insulation R value sounds completely inadequate for your northern location. It sounds like you are trading off R value for a 'texas basement', but that may be a poor tradeoff in the end. You need to bring that R level up to the current code requirements. A 6 mil poly vapor barrier stops air movement when applied properly to keep warm air movement from flowing into the cold space. If you do not have a poly barrier you are for sure getting alot of air flow from inside and condensing both under you OSB as well as warming the cold attic space where it will condense on the roof sheathing for instance. Even if more venting reduces the amount of mold on the roof structure you will still have it under the OSB if this is not completely addressed.
Old 04-07-11, 05:07 AM
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The issue is the source of moisture. It is most likely flowing into the attic with warm air from the house. Air leakage is common and needs to be sealed, everywhere possible. Once that is corrected, I would suggest you re-install the attic floor elevated another 6" for proper insulation. Your area actually needs even more than that, but 12" is better than 6".

Here is a link to help locate those leaks:

Old 04-07-11, 03:25 PM
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Thanks for the info. I had often wondered if I had enough insulation. You guys confirmed that idea. Thanks again, guess I'll be raising my floor and adding more insulation.
Old 04-07-11, 07:20 PM
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Sounds like you need to reduce the rh in the living area. Once this is done your moisture issues will go away. I agree with the others that u need more insulation. But that's not causing the mold issue high rh in the living space is
Old 05-03-11, 02:35 AM
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Recommended Levels of Insulation : ENERGY STAR
Ridge vents is all you should have needed on the roof. By also having gable vents and a gable fan you've defeated the whole idea of the ridge vents. Now once the fan turns on it's sucking air backwards though the ridge vents instead of though the soffit vents so there's no air flow over the back side of the sheathing to dry it out.
You do have soffit vents right? There should never be insulation laying out beond the tops outside walls. Those soffit vents need to be kept clear. Foam baffles may need to be added. There should be a 6 mil. vaper barrier on the ground under the house held in place with 16" long insulation ties bent in half, and automatic opening foundation vents. (any home store sells them)

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