"I have a plastic liner on the floor now. Isn't this good enough"?
In a typical 1200 square foot crawl space, anywhere from 10 - 24 gallons of water can be evaporating from the soil every day. Having a plastic film on top of the dirt floor is never a bad idea, and in most areas, is required by code. The problem with just doing that is you still have moisture entering through your foundation vents, your foundation walls, and any seams in your plastic sheeting, which will probably result in humidity levels well above 65%.
"Should I remove my floor joist insulation"?
If your floor joist insulation is damaged by moisture, it should be removed as it has likely lost most or all of its insulating value. If it is still in good condition, it can and should stay in place.
"Should I insulate my foundation walls"?
Insulating your foundation walls is the best option, but only in one of two situations:
1. Your floor joist insulation has been damaged by moisture or mold, and needs removal.
2. You have no insulation in your crawl space.
We use 2" rigid foam-board insulation on foundation walls. This type of insulation is relatively impervious to water and insects. After the liner is installed over this, your crawl space temperature is primarily maintained by the earth, which is a relatively constant 68°F, year round. Cold floors are history.
"Which is better - conditioning the air or dehumidification"?
Because both methods will get the job done, each crawl space must be evaluated individually, along with the owner's preferences. The most important considerations are:
1. Will there be floor joist insulation in the "ceiling" of your crawl space?
If you have floor joist insulation, and you condition the crawl with your home's HVAC, you can inadvertently create a "refrigerator" under your home. If the temperature in your crawl is 10°F cooler that the living area, relative humidity can increase by 25%, which might be enough to stimulate mold growth. Conditioning the crawl generally requires the removal of the floor joist insulation, and the installation of foam board insulation on the walls.
2. Conditioned air requires no maintenance in the crawl. A dehumidifier does, although not much.
3. A dehumidifier will absolutely dry your crawl space to safe levels. Conditioning will sometimes fall short, especially when the HVAC system is either under-sized, or inefficient.
4. Installing supply and return ducts typically costs $300-400. A good quality crawl space dehumidifier will cost $1,000 or more.
"Do I need a drainage system and sump"?
Some of my competitors will try to sell you this component, whether you need it or not. In reality, unless your home is on wet-lands, on the down-side of a sloping terrain, or on a lake front, you probably just need to properly manage your rainwater, even if you now have standing water in your crawl. Again, each situation is unique, so get the advice of a professional, then decide.
"Can I just close the vents and install a dehumidifier"?
Yes. This will definitely lower the humidity level in your crawl space, but...because moisture will continue to enter your crawl through the "closed" vents, as well as through your porous foundation walls, your dehumidifier may run continuously, and likely burn out in the first year. And...whether or not the dehumidifier you installed will pull the moisture down below the 60% threshold, is questionable at best. Sorry, but you are rolling the dice on this one.
"My Pest Control Company wants to sell me auto-closing vents. Is this a good investment"?
An "auto-closing" vent is a simple device that closes your foundation vents at 38°F, automatically. It does save you having to walk around your home for ten minutes twice each year to open or close the vents. We believe that installing a set of these is roughly equivalent to putting a "tire shine" product on a flat, or taking a shower while wearing a raincoat. In addition to not addressing the real issue in your crawl (moisture), these vents are made from plastic, and have set screws to hold them in place. When first installed, the screws hold tight against your vent openings, but we all know what happens to plastic products under stress...they either flex or break. We do not recommend them.
"Should I use a fan blowing out one of the vents to help pull the moisture out of my crawl space"?
No! If the humidity is very low outside, this might reduce the moisture in your crawl. But, if the humidity and/or outside temperature is higher than your crawl space, you could actually be adding to the moisture already there.
