Dehumidifier in Crawlspace - Do I need to worry about "makeup air" (Atlanta: house)

[jweikert]

Hello

I have some dampness in the crawlspace of my ranch style home in Atlanta. I had a mold issue that stemmed from the 500 year flood and a leak in a drain pipe under the house. Since the dampness went undetected for a long period we developed a mold issue. Had the house tested and yep, there was mold spores and molds at high levels. Took care of the crawl space by killing mold and putting down thick plastic everywhere. Sealed gaps in floor etc so make the main floor more protected. Still concerned that while the crawl space is dry overall there is some dampness and I'd like to keep any mold from growing back.

My repair guy suggested I close/seal all of the crawlspace vents and then get a dehumidifier and run it with a humiditstat - let the water drain into the AC pump that will carry it outside. I like this idea and it seems to be reasonable from everything I have researched. However, I have my furnace/AC unit and my hot water heater in the crawlspace. If I close off the crawlspace vents and run a dehumidifier will I have any issue with the gas water heater or AC unit?? I read that these devices require something called "make up" air and also may need ventilation themselves or open air. So my question is....is it a good idea to close the crawlspace vents and put this dehumidifier down there or is there a better solution?

Note we have lived in this house for 25 years and never had any issues with moisture until the flood and the leak......but it is humid in Atlanta and the outside air is essentially what flows thru the crawlspace.

Thanks a bunch.

Jeff

[Bbrash1]

The ventilation issue has been a common debate, even with attics in humid area.. Keep in mind that if your house is built on clay soils,oncewetitishard to dryout. Once dry, the crawlspace may be ok with vents. You may need to check the drainage around your house to ensure positive drainage away from you foundation.It might not be a good idea to modify ventilation with a gas water heater in a unventilated area. I could consult a licensed building professional to ensure safety and code compliance.

[BobKovacs]

The makeup air for the furnace and water heater is an issue even if you didn't have a dehumidifier down there. You need to have an HVAC company figure out the proper size openings to pull makeup air into the crawlspace, as well as where to pull it from.