I just bought a house in Kentucky that has a 1300 sqft crawlspace with no insulation or vapor barrier. The backyard slopes towards the house, and the water table is high, which means the crawlspace is almost always damp. We have to keep a dehumidifier running inside the house to prevent mold. I'm planning to encapsulate the crawlspace and am curious about the necessity of a dehumidifier down there. If the crawlspace is sealed and air exchange happens with the inside, why does humidity still build up? Since our indoor air is dehumidified by the AC, wouldn't that keep things dry as well? On that note, can I save power by replacing the dehumidifier with a humidity-controlled fan that only runs when the outside humidity is lower than inside? Why doesn't this seem to be a common solution?
3 Answers
I recently encapsulated my crawlspace, and even though it’s fully sealed, I've noticed humidity levels down there hover around 80%, while my living area stays at about 50% with the AC. The ground moisture and outdoor humidity really play a part in this, even when the setup looks good. So, in our case, it’s clear that a dehumidifier is still necessary despite encapsulation.
Your crawlspace isn't airtight, which means it 'breathes' and is constantly equalizing with the outside air pressure. This can lead to condensation when warm air hits the cool walls of the crawlspace. A dedicated dehumidifier is designed to handle this issue efficiently. I use an Alorair model in my basement and it works wonders!
After encapsulating my crawlspace last winter and installing sump pumps, I've observed that despite outdoor humidity levels being pretty low, the cool environment down there can lead to high humidity levels. I have a good dehumidifier paired with humidity sensors that automate its operation, and it suits my needs perfectly. It’s crucial to monitor conditions down there!
It's interesting that you see such a high difference. I find it confusing, too, since the crawlspace is sealed and there shouldn't be much moisture coming in. Are your vents sealed off?