In recent years we’ve seen a dramatic increase in the number of Tideland served homes that now have crawlspace dehumidifiers. It’s a concerning trend for a number of reasons.

We’ll refer to a recent energy audit to address our concerns.

In this particular case, the dehumidifier load was fairly easy to isolate because the home is unoccupied and the only items using energy are the crawlspace dehumidifier, a single indoor lamp, and a chest style deep freezer.

During the months of July and August, Tideland territory received over 25 inches of rainfall. That’s more than double the amount of precipitation we normally experience during those months. Those circumstances alone would necessitate the need for longer dehumidifier run times.

To access Advanced Energy’s 4-page quick reference on closed crawl spaces and other materials visit crawlspaces.org

The home we visited in August is a two-story residence built in the 1920s. It had an Aprilaire model 1850 dehumidifier capable of removing 95 pints (11.9 gallons) of water per day with a rated airflow of 245 cubic feet per minute. The unit’s compressor had an operating wattage of 960 watts (8.0 amps multiplied by 120 volts). In conjunction with the compressor operation, there was a 135-watt fan that moves the air across the coil. There was also a 228-watt condensate pump that moves the condensate from the drain pan to the outdoors. Together, these three components were contributing over $100 to the member’s total electric bill.

We want to note that this is a larger dehumidifier than we typically see in a residential setting. Based on the home’s footprint we are hard pressed to understand why such a large unit was installed by the contractor. However, even at half that size, the additional energy expenses would be significant.

Even more concerning was the condition of the crawlspace where the dehumidifier was located. The crawlspace was not truly encapsulated.

Encapsulation means that the crawlspace is sealed off from direct communication with the outdoor environment. Consider for a moment trying to heat or cool your home with one or two windows open. That would be a very expensive proposition and that’s why we close them before we turn the HVAC unit on. It’s also why generations of parents have told their children to not stand there with the door wide open.

Yet during the vast majority of our audit visits, we do not find true vapor barriers underneath homes. Yes, there may be sheets of plastic but most often you can still see dirt because the vapor barrier material isn’t continuous, seamed and sealed. Even fewer vapor barriers continue up the home’s footers and foundation walls.

That combined with unsealed air vents and crawlspace access doors and improper grading creates a vicious cycle of dehumidifier operation. The dehumidifier that was intended to be a cure now becomes just another symptom of a problem that has not been holistically addressed. In the meantime, energy consumption increases and sometimes dramatically.

Before embarking on the journey of owning and operating a crawlspace dehumidifier, we’d like to encourage you to visit crawlspaces.org. The site is hosted by North Carolina’s Advanced Energy Corporation, a nonprofit energy consulting firm.

One thing to point out: crawl space encapsulation is an investment. But when done properly it should last for the life of the home. In fact, once proper encapsulation is complete it may only be necessary to dehumidify the crawlspace one time to get it in balance, thus foregoing the expense of purchasing and maintaining a dehumidifier.

If you already have a dehumidifier and want to reduce energy consumption we recommend that you check the unit’s settings. Be sure to take advantage of any energy-savings modes or lower fan speed settings. Clean air filters regularly. Ensure proper drainage to prevent condensate build-up.