I had a bug issue at a rental and discovered some pretty extensive white fungus on the floor joists under the house.

I've had two "crawlspace solutions" companies out to look and quote me thousands of dollars in remediation for "MOLD" (which I know is a trigger word).

I already have a working sump pump, vapor barrier, and batt insulation. It is completely dry under there right now.

The companies have tried to sell me a better sump pump (plumber says pump is fine), a commercial "crawlspace dehumidifier" (makes sense but does it need to be the super expensive model?), a heavier gauge vapor barrier (sounds like an upsell), sealing of vapor barrier up walls and piers (could be useful, but really required?), sealing the outside vents (sounds useful), new plastic-wrapped insulation between the joists (insulation company says it's unnecessary), a French drain (could be useful, but questionable whether it's required), and a spray of fungicide (sounds like as long as it dries out, fungus will die without fungicide).

I think that what I need to do is seal off the vents to the outside and add a standard household dehumidifier, which I can get from amazon for about $230, since it's a pretty small space. I can drain it right into the sump pump. This should reduce the humidity under the house to the point where the fungus will dry out and stop growing, right?

Does the humidifier purchase seem logical? What might I be missing?

Oh, and I'd add one more thing: a hygrometer with a probe stuck into the crawlspace from the utility room so the humidity level under the house could be easily checked.

Anything else?

You can do it one of two ways - one is to seal the vents and put the dehumidifier in. You will also want to put a box fan or small fan to circulate the air. Cover your sump pump too assuming water can still get into it. You don't want to dehumidify a puddle of water that you are creating.

The other option is to put a radon fan or other higher CFM fan at one vent and let it pull air in the other vents and out the fan. The forced airflow will help with the humidity. You can get them online or Amazon.

Definitely get the water out. Start with redirecting the water outside. Downspouts and grading will work wonders.

Then work on the water that makes it inside the crawl. I always worked with crawl vents until my place. It is sealed up completely. Insulation up the foundation wall into the ribbon board. I have great grade and a drain system with an outside perimeter. Downspouts are also connected and end up out at the ditch far away.

Put gravel in the crawl, then plastic and then more gravel. I didn't put it up the wall, although that would be fine. There is zero water in the sump pit. Never has been any.

I also have a basement and inside perimeter drain with it dumping into another sump pit. That pit is directed out to the drain on the outside perimeter of the house.

My old place had some moisture issues. I put heavy plastic down, glued to the perimeter. Had two sumps on opposite sides on the crawl. I also put a dehumidifier down there and let it run at a certain level. Got it from a foreclosure.

Laura,

Locally we often see a fine white powder on the floor joists.

I pay a grunt worker $100 for about an hour of work because it's grunty - to lay on his back, wearing a checmical breather mask, to spray mold killer on the wood. Yes he is adding moisture but the chemical stays on the wood. to prevent future growth.Had to do this many times to please house inspectors when selling a flip.

We will also set one or two carpet style fans in the crawl opening to blow out the opposite side. Run for a week and dry out the crawl and wood. FAST MOVING AIR is proven to pull moisture out of wood much more than just regular fans.

BRAD