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Community and Q&A

Controlling Moisture in an Attic

mhettrich | Posted in General Questions on

I’m located in Long Island, New York. I’ve recently discovered a large population of insects (psocids) in my attic. These critters apparently thrive in areas of high humidity and where moisture is present, thus leading me to try to find issues with moisture in my attic. The attic seems to be well ventilated, with soffit vents and a ridge vents along the entire length of the roof. I’ve had the attic inspected by two different people who both did not see any issues with mold or excess moisture. Both also said ventilation was adequate.

In terms of temperature humidity, during the day in the summer temperatures will be above 100 degrees with RH in the 20-30% range. Overnight, the temperatures drop into the 70s-80s and humidity rises into the 60-70% range. Humidity levels in the house never rise above 55% typically sitting in the high 40% area, though I’ve been considering using a dehumidifier to lower the levels even further

There are three areas that I can potentially identify that may be causing a moisture issue.

The first is the fact that the people who built the house vented the two bathroom fans directly into the attic. I understand that this needs to be rectified as soon as possible and that I should have those run to the roof and out of the house. I am attempting to contact a roofer to have this done.

The next is the pipes for my air conditioning in the attic. During periods of excess heat and humidity, they definitely sweat. I think this is fairly normal, but perhaps I could add insulation to the pipes to help prevent condensation from forming on the pipes?

Lastly, I do know that my attic is in need of air sealing and better insulation, as there is only fiberglass up there right now and nothing has been air sealed, which I assume can result in a lot of moisture and conditioned air entering the attic. I’ve been looking into having air sealing done and then having cellulose blown in to add to the insulation.

Any advice that someone could provide would be greatly appreciated.

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  1. Jon_R | | #1

    Note that attic humidity isn't a single number. For example, while the air may measure 50%, right under condensate drips will be a psocid friendly 100%.

    > conditioned air entering the attic

    In Summer, this make the attic drier.

    I'd focus on air tight, spray foam encapsulated ducts.

    1. mhettrich | | #2

      Very True, and that's why I am going to such lengths to try to eliminate sources of moisutre. I definitely plan to have my pipes up there insulated properly. For the most part they are, but there are a few areas that were done pretty shoddily from the looks of things. Any recommendations on what to use to do so?

      1. Jon_R | | #3

        I'd look for a company with experience in duct leakage testing and in closed cell spray foam "duct encapsulation".

  2. the74impala | | #4

    My gut job of a house has a history of a significant number of Japanese beetles (look like lady bugs) and cluster flies. There were some hanging out in the attic spaces, but they came out of the walls. The leaks in the roof that went into the walls, and the poor sealing of the walls all lead to the infestation. I don't think I will have either of these issues when I get done. They don't need much space to get from the wall to the attic, so air sealing would be a big help.

  3. charlie_sullivan | | #5

    All the things you suggest are good ideas with the idea to fix the bath fan venting the one I'd do first. But eventually, doing everything you list will pay off in efficiency as well as moisture control.

    1. mhettrich | | #6

      Thanks, Charlie. I've also noted that some of the wood in the attic appears to be "sweating" tiny beads of sap. I've read that this can be normal in high heat, but is it indicative of an issue?

  4. plumb_bob | | #7

    Looks like you are on the right path, you have identified 3 major problems and fixing those should lower the humidity in the attic significantly.

    How does the underside of the roof sheathing look? Any mould?

    Some species of wood will push out sap over time, I would not be too concerned with this.

    1. mhettrich | | #8

      Underside of the roof looks great. No mold to speak of. The inspector I had out actually commented that all the wood in the attic was in some of the best condition he's seen.

      Another question. Do ridge vents need to be cleaned? Just curious if maybe the air-flow could be sub-optimal.

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