Crawlspaces are supposed to be a humid place… that’s normal, right?
Normal does not mean correct or ideal.
As folks who go into a lot of crawlspaces, we can assure you that the vast majority are not places you want to spend much time in. Messy, dirty, humid, wet, full of insects, and hard to get around tends to be the norm.
But carpet in a bathroom was common too, and we all realized that was a bad idea.
A crawlspace doesn’t have to be all those terrible things, and you’d be better off if yours wasn’t.
If it’s all out of sight, though, why does it really matter? If the only time anyone needs to go down there is to fix something, it’s someone else’s problem.
Unfortunately, no. The way our houses are built the crawlspace and house are far more connected than they appear. The flooring between the two spaces is far from airtight, meaning whatever is in the air of the crawlspace, be it mold, fungus spores, or humidity, is also in the air of the house.
So, what’s the problem with crawlspace humidity?
Higher humidity brings with it the possibility of many issues. Lets look a a few of them.
Mold, fungus and dust mites all enjoy a humid environment. Small amounts of mold and fungus are present in the air just about always and everywhere. To live they need a survivable temperature (above freezing and below about 140), a food source (think most organic materials) and an ideal humidity level (anything about 60%). Basically, we live the same as mold and fungus. They prefer the temperatures we live at, as well as our great food sources for them, such as our own food, what we wear, or what we build our house with. The only line of defense we have against them is controlling the humidity to where they can’t live and thrive.
If you want a house thats mold and fungus free you have to keep the relative crawlspace humidity below 60%. If you make it too dry, your skin and mucus membrane in your nose starts to dry out at levels below 30%, so our sweet spot is about 35-55%.
Humidity also plays a big impact on comfort. If you’ve lived in the South East for any time this doesn’t require any explanation. A warmer dry temperature will feel more comfortable then a mildly cooler more humid one.
Many items in our home swell in high humidity and shrink when they dry, such as wood floors and moldings. If your house maintains a consistent humidity, all of your wood products will stay far more stable. This will reduce waviness and cupping in hardwood floors, gaps opening in trim, and close those doors that don’t close seasonally.
Mechanicals last longer with consistent humidity as well. Humid crawlspaces are prone to condensation on water lines, ducts, air handlers, and just about any other metal surface. Which means over time those things tend to rust and fail.
A dry crawlspace leads to a happier home that’s more comfortable and healthy to live in.
