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Crawl space mold

nepal | Posted in General Questions on

1st off, where are my manners, thank you Martin for your answer regarding using damaged 4″ roof mate for foundation walls. i did ask my building inspector about it as well…i was thrilled that he said yes and i didn’t need to apply a fire-barrier like drywall to it. my guess is, because it’s only 2′ high and there is absolutely no storage in it. He did say i should cut a hole/vent in the floor (from that crawl space to the main floor) i have been plugging away at removing the old R40 around the perimeter, closing off the vents or plugging them up and installing the 4″ roof mate in the rim joists as well as on the foundation wall (sealing along the way with great stuff).
i do plan on laying a new, white 15 mill vapor barrier on the dirt floor, taping to the foundation wall as the old 6 mil clear was not installed properly and it is trashed.
2 questions please….
#1… there is a small amount of mold on some of the joists (mostly near were the old vents were). did i see in one of your answers before regarding mold that it would go away by itself if the crawl space was properly sealed and dry? I can’t help but think it would be a good idea to attend to it before laying the new vapor barrier. is there no solution that can “just be sprayed” ? must it be scrubbed as well? i hate to sound lazy.
#2 …this is a summer/winter getaway cabin. i turn the main electric breaker off when i leave. .should i be thinking of a dehumidifier and leaving the power on? is it possible that after a short while (if sealed properly) there will be no need for a dehumidifier? i don’t really like the idea of small bathroom type fan in the crawl space venting to the outside but your thoughts would be appreciated
i should also give you one more bit of info. the only source of heat in this 1000 sq ft cabin is a regency warm hearth fireplace in the middle of the building. this unit has ducting off it into the crawl space were it is ducted to the bathroom, kitchen and back bedroom. it’s great. i was thinking off putting another vent/register from it, in the crawl space to help heat that crawl space, which will in turn, help get the floors warmer.
thank you in advance for your thoughts…very much appreciated

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  1. GBA Editor
    Martin Holladay | | #1

    Once you remove the source of moisture (and once the materials you are worried about are dry), mold won't grow. If you want to remove dormant mold from framing lumber, ordinary detergent and water will work -- you don't need bleach. Just be sure that the materials can dry after they have been cleaned.

    When a damp crawl space is converted from a vented crawl space to an unvented crawl space, it's often a good idea to run a dehumidifier in the crawl space for a few months until everything dries out. After a few months, if the space seems dry, you can turn off the dehumidifier and remove it. Keep an eye on everything, though -- if moist conditions return, you may have to investigate why. Use common sense.

    As I noted in my article, Building an Unvented Crawl Space, building codes require, and building scientists recommend, that sealed crawl spaces have a little bit of air exchange to keep the relative humidity of the crawl space under control. You can either use an exhaust fan or a forced-air register to accomplish this goal, as noted in the article. As long as you don't get in trouble with your local building code official, you can experiment with different approaches if you want.

    The proof is in the pudding: If your crawl space is dry, your method is working. If your crawl space is damp, you need to make some changes.

    -- Martin Holladay

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