The purpose of foundation vents is to allow passing air to carry moisture out of crawlspaces. Except in particularly dry climates, that often isn’t suitable. Even in warm hot summer months the humid moisture laden air will condense on the cooler foundation walls, pipes, ductwork, and even the underside of the flooring. Moisture, still air, and relative darkness is the perfect breeding ground for mold and mildew.

One mold inspector/technician I know recommends leaving the vent’s open year lengthy (trim hedges or other obstructions back to allow better air flow) and plus wiring the crawlspace with low wattage lighting to run 24/7.

These tips will help keep your crawlspace dry and mold free:

1. Create Better Drainage around your home to prevent rainwater from seeping under the foundation. Grade soil to about .5 inch per foot. Import the soil whether essential, whether you’ll pardon the pun, it’s dirt cheap. that step is highly recommended even whether you have gutters to direct the rain water coming off your roof. whether you do have gutters, construct certain the water is directed away from the downspouts and not pooling back to the foundation.

2. Insulate the Exposed Foundation walls with 1.5

inch rigid, moisture-proof insulation such as Thermax, taping the seams. It would additionally be a good notion to use that same insulation to insulate the rim joists (the joists that sit atop the foundation walls) and caulk to prevent air flow.

3. Cover the Dirt Floor of the crawlspace with a heavy plastic (10-20 mil) moisture barrier. You want the barrier to be mostly continual (a few accidental holes wont undo the protection and may even help puddles from heavy rains or a busted pipe drain off) so overlap and tape the seams. Attach the plastic at least 6 inches up on the foundation walls.

4. Cap the Interior of the Foundation Wall with a strip of the plastic sheeting and galvanized flashing to complete the moisture barrier. The flashing will additionally serve as an obstacle to termites (not a complete defense, just a part of your control program.

Better moisture control not only helps prevent mold and mildew growth, but plus will help to extend the life of your ductwork, plumbing, pressure tanks, and hot water heaters located in the crawlspace.

Original post by NewB