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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?

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The answers so far indicate you'll be making a long run. (I concur) Just wanted to add, don't make long runs with flex duct, use as much smooth duct as you can. Avoid any more bends than absolutely necessary. – bcworkz Jul 22 '12 at 20:23
venting into closed spaces will always result in excessive moisture and condensation. DO NOT DO IT. Always vent to out of doors. – shirlock homes Jul 23 '12 at 10:49

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.

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And food stock for mold. Despite the lint trap, fiber gets blown anywhere the discharge air goes and deposits as a fine layer all over everything. Natural fiber is a cellulosic food source for fungi and it's associated life form mold which are built to break down plant fiber. So, you're creating the ideal environment for mold growth. Low heat, lots of moisture and food. Enjoy the results. (Yes, lint traps are very inefficient at fiber removal, I already dealt with an attic space where someone had this idiotic idea.) – Fiasco Labs Jan 26 '13 at 19:10

I doubt it. They might help in the spring when they are open, but definitely not in the fall/winter when they are closed.

Vent it outside to avoid any issues.

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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.

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This is a good point. If the house is forced hot air and the property is in a cold climate, the house will be very dry in the winter. However, still a better idea to vent outside. – ssaltman Mar 6 '15 at 18:14
Never vent a gas dryer indoors. Carbon monoxide and all that. For electric, if you have dry air, heck yeah. Vent it indoors. Filter the lint as best you can, but if it is a problem, at least indoors you will notice and do something about it. I would never vent into a crawl space. – mkeith Mar 7 '15 at 7:45

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.

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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.

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If it's a gas dryer, absolutely do not do this. You're exhausting fumes into your house. Even if it's electric, this is still a really bad idea. Unless you live in a super-dry climate year-round (antarctic?) you will definitely end up having moisture problems somewhere in that house. – DA01 Jan 29 '13 at 4:57

Your dryer puts out dry heat not moister,its not vented from wet clothes its vented or excess heat ,there is nothing wrong with it in your crawl space,mine has been under the house for 10 or more years and in the winter my floors stay warm when the dryer is running

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David- You should verify your facts before you submit an answer. I realize you are probably answering from personal experience and observation, but this may not apply in someone else's location. Please check the IRC for up to date codes. Just so you know: a dryer's exhaust is anything but dry heat. It is mostly water vapor extracted from the clothes by the dryers heat source and expelled into the outside atmosphere. It is for just this reason that the dryer vent should not terminate into a crawl space. Moisture inside a building will have detrimental effects on the house structure. – ojait Jan 29 at 2:53

I have a large basement and use the dryer only once or twice a week . I really can't see a moisture problem with venting inside . People hang up wet clothes inside don't they ?

The only problem I can see is if you use that stinky stuff , Bounce.

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Try weighing a basket of laundry before and after drying it: that's the amount of water you're venting into your basement. – Niall C. Jan 26 '13 at 23:49

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