Removing Moisture and Allergens from a Crawl Space

Get rid of mold and mildew smell by installing a fan to force moisture from your crawl space. Great solution for those who have mold/mildew allergies. This works for an open crawl space.

I had an issue with moldy air at my father’s family cottage. We would go up there on a damp spring day and his sinuses would go crazy; sneezing, scratchy eyes, and stuffed up.

When we left one Sunday night, I placed an ordinary box fan over our utility hatch so it would blow into the crawl from the cottage living area. I hoped this would take dry air from the cottage, drive it into the crawl space and push the damp crawl space air out the foundation vents.

Six days later, it’s Saturday after work. Dad and I arrive at the cottage and I’m anxious about the status of a cheap box fan running 24/7 since the last Sunday night, but it was still running and not too hot either. And the cottage was like a breath of fresh air when we walked in! Now my next mission was to make this system safe.

I purchased a totally enclosed, continuous duty fan rated for 2,000 cubic ft. per minute that draws less than 3 amps. I mounted it to the bottom of the floor joists. The floor here happens to be my access hatch. I cut 3 separate 4×12 floor registers openings so air can flow to the fan and I can easily protect the opening. To operate the fan, I installed a timer and wired it to a gfci receptacle in the crawl space next to the fan. It provides a safe and inexpensive disconnect when working on the fan.

For additional protection, I added a 3 amp fuse to the timer controlling the hot wire to the fan. That was so that if the fan ever has a malfunction, it would draw extra power and blow the 3 amp fuse long before it would trip a 15 amp circuit breaker.

I have it run for an hour in the evening every day. I feel the air in the cottage is the driest then and it will do the best to keep the crawl area dry.

The Big Bonus to the fan is the way it makes keeping the cottage clean. I use a 30 inch floor mop, push it around the cottage and shake it over the running fan. The fan sucks the dust out of the mop, and with 3 trips around the cottage, it is clean as a whistle.