We have a crawl space with a combination of sandy and clay soil in it. The crawl space is about 3' deep. To eliminate a long dryer vent run, I'd like to vent the dryer directly into the crawl space. We have vents built into the foundation that I open each spring and close in the fall. Will this help dissipate the moisture enough to prevent mold?
Vented air from the dryer is full of moisture since it contains water from the clothing being dried. Do not vent it into your crawlspace or basement since you will definitely have moisture problems. After you vent it outside, run the dryer and put your hand over the vent and you will see what I mean.
The answer is no. I live in a 4 unit apartment. My neighbor vents their dryer into the crawl space. I have the following problems:
My house is extra hot in the summer due to the moisture in the air creating a humid environment.
There is dust, dirt, and lint stuck to everything in my house.
My family portraits of my 4, 3, and 2 time grandmothers are ruined.
My shower grows mold like crazy. (I have lived here 25 years and never had a mold problem in the shower until they moved in 3 years ago.)
I am breathing that lint all the time.
The ceilings are opening up and sagging, the outside walls are buckling.
So no don't do this to yourself.
WHAT??? It’s okay because I’ve done it, a friend has done it, or it’s warm moist air so you can’t do it is CRAZY.
How about it’s ILLEGAL.
The code says, “Dryer exhaust systems shall be independent of all other systems and shall convey the moisture to the outdoors and shall terminate on the outside of the building.” (See ICC M1501.1)
I'm guessing nobody in here uses a humidifier in the winter? (Screw weighing your clothes before and after drying... measure the amount of water multiple tanks you may use daily goes into the house and the fact your being inefficient while doing so)
I have to laugh at all the people going crazy about NVR VENT INDOORS. I run an indoor line (with additional fine screen trap) in the winter time when the house is cold and dry. This keeps my energy "waste" to a minimum in the part of the year my solar panels lose a lot of effectiveness and helps my "on grid" time stay at a minimum.
No mold/lint dust issues and I've been doing it for years now.
Since you are looking at your dryer vent, but don't mention climate or type of dryer, I will mention a few things. It is considered unsafe to vent a gas dryer indoors because the combustion fumes go into the vent also. Carbon monoxide and all that.
If you have a very dry climate and an electric dryer, vent it right in the laundry room (you can add an additional lint trap) to help with humidity and warmth. If it causes a problem in that room, it will be obvious and you can deal with it. I would not vent into a crawl space, because if there is a problem with lint, condensation or mold, you won't notice.
If you do have to do a long run, keep it as straight as possible. And if you live in a cold climate, I would suggest that you insulate the duct works in the sub floor area. This helps prevent condensation from forming on the inner duct wall. This condensation helps pick up lint, and eventually the whole vent pipe can clog. Then you will have to go back into the crawl space, take the ducting apart and figure out what happened. Personally, I try to spend as little time in crawl spaces as possible.
My mother vented her dryer into her basement for warmth down and upstairs (floor, open joists) and never a moisture issue at all. Ran it through a T with a door and had pantyhose on the end. It was very easy to tell when to clean out the pantyhose.
I'm about to do that to mine, it's in an unfinished 2 car garage/shop area. I think it all depends on how many loads you do and size of area it is before I would even wonder about moisture concerns. I have to get parts, maybe I'll post a picture afterwards.