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Boric acid or concrobium in stud cavity before insulation (in cold climate)

maxwell_mcgee | Posted in General Questions on

Hi folks,

Curious if anyone has ever tried spraying exterior stud cavities with Boric acid spray (or similar) prior to insulating in a colder climate (I’m in climate zone 5/6). 

We got the roof on and (mostly) sealed on our new build in the winter months, but there’s a lot of moisture in the assemblies including the stud cavities. It’s going to be impossible to let it all naturally dry out fully before insulation goes in. 

I’d like to spray something in the stud cavities before insualting (we’re going to use rockwool) to prevent mold and pests in the future. I know Rockwool itself is mold resistant, but want to prevent mold from growing on the studs, back of the drywall, etc.

I’m pretty sure in warmer climate zones builders often spray the cavities with something to reduce termite risk before insulating. What is that? And would a similar technique work in a colder climate? Especially if being sprayed in the winter?

Thanks in advance!

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Replies

  1. bcade | | #1

    The product you’re referring to is probably something like Bora-Care with Mold-Care, which covers your bases whether mold, fungi, or wood eating insects. If you’re already sheathed you’ll be missing the faces of studs, but it’s definitely better than nothing.

    We started using Concrobium as cheap insurance against mold after some unexpectedly wet winters, and so far (knock on wood) haven't found any mold on treated surfaces. One of our motivators is that Concrobium can be applied via a fogger, just fill it up, plug it into a timer set for a few hours at the end of the day, then the fog has time to build up, saturate surfaces, and disperse before workers return the next day.

    One other thing to consider is renting a dehumidifier to remove as much moisture as possible before insulating.

  2. maxwell_mcgee | | #2

    Thanks! Super helpful.

    Curious, what climate zone are you in? Also, any perspectives on using a fogger in colder temps? our house is temporarily sealed (window rough openings are tarped over) but not yet heated so while the indoor temps are generally above freezing, there’s still a lot of pretty cold spots.

    (We’re expecting sub-freezing temps for at least the rest of January according to the long range forecast.)

    1. bcade | | #3

      I'm in 3C, the central coast of California. It never gets below freezing here so I have no firsthand experience, though the fogger instructions specify between 5–32° C (41–89° F).

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