Billy Tesh, President Crawlspace Depot, LLC
1. Should I duct my unit? In what situations would I duct a unit?

Ducting is usually not necessary but is sometimes needed when air flow is restricted. For example, additions, L-shaped areas, separate “rooms” or very uneven levels may restrict air flow. Ducting can be added later if monitoring indicates a problem. It is recommended to always duct on the supply side of the dehumidifier with flex-duct, then duct into the remote area, or split the duct and push air into multiple areas. Monitor with a thermo-hygrometer so you can adjust as needed.

2. Where should my unit be placed in the crawlspace?

There’s no universal answer because every crawlspace is different. In general, a central location is obviously best, and even though the units are quiet, avoid placing them under bedrooms. Available drainage is a factor, as is a power source — no extension cords, please!

3. How/where do I drain the water?

Again, this can vary quite a bit, but the idea is to find the best exit area to get the water out of the crawlspace and safely away from the foundation. Drain to:

  • Positive drain
  • Gravity to the exterior
  • Condensate pump
  • Sump pump
  • Use existing systems (HVAC condensate line)
4. Do I need to hang the unit or can I just put it on the ground?

The unit should perform well either way. If you hang a unit, it gives you more elevation for a gravity drain and you can place a condensate pump underneath if needed. In lower crawlspaces, placing the unit on the ground may be necessary. Just make sure it’s not directly on the ground by using risers, and make sure it’s level. Our individual risers make this a lot easier to do.

5. What size unit do I need for my crawlspace?

There’s probably a threshold of about 3,000 square feet for most 70- to 75-pint dehumidifiers. For crawlspaces of unusual size and/or unusual moisture problems, larger or multiple units may be needed. Always monitor your space and shoot for a relative humidity that’s in the range of 50-60%. You don’t want it too dry because that can shrink wood joists or flooring. Too wet, and the possibility for mold and wood decay fungus increases. Keep in mind a properly closed crawlspace has very little moisture exposure. Our studies show less than 3 pints per day per 1,000 square feet.

Risers serve two purposes: 1) They separate the unit from the ground when you aren’t hanging it and 2) The right kind of riser can help you level the unit. Crawlspace Depot’s riser kit has two different size risers that you can mix and match for three different heights.
Correct installation is essential for operating efficiency and to maximize the life of the unit itself. Making sure the unit is level is a critical part of that process, whether it’s hanging or on the ground.
Condensate pumps are especially useful when you do not have enough elevation to drain your dehumidifier by gravity, even when it’s hanging. This easy solution allows for the water to be pumped in any direction through tubing to the outside of the structure.