It sometimes happens that one of my columns will spark lots of questions from readers, as was the case with a past column on dryer venting.

Judging from the questions I’ve received, there’s apparently a lot of confusion and misconceptions about the subject of dryer venting, and a lot of people are struggling with misinformation that they’ve been gathering from friends, the Internet or other sources.

So it seemed like a good time to revisit this topic, and clear up a few misconceptions:

Misconception No. 1: It’s OK to vent the dryer directly into the house, so that the air can be used as either a source of humidity or a source of heat.

Definitely NOT! As the clothes dry, moisture is being removed and vented out of the dryer, which is why it’s so important that clothes dryers be vented all the way to the outside of the house. If not, you’ll be pumping a tremendous amount of warm, moist air directly into your home, which is a perfect recipe for creating mold growth, as well as potentially doing a lot of structural damage. That air also carries with it a lot of fine lint particles. That’s not something you want to be breathing, and in high-enough concentrations the lint is highly flammable.

Misconception No. 2: For dryers that are located in a place where venting to the outside is difficult, it’s OK to simply vent the dryer into a container of water.

Nope. When a dryer is in operation, it’s removing moisture and lint and venting it to the outside. The only reason that people vent dryers into water is to contain the lint so it doesn’t fly around. But that does nothing to solve the problem of getting the moisture out of the house; in fact, pushing moist air into a bucket of water simply makes the problem worse.

Misconception No. 3: Putting an exhaust fan into the dryer vent pipe will boost the dryer’s performance, especially over long distances.

When the duct has a long way to go from the dryer to the exterior wall, a booster fan is actually a good idea. It can help improve the flow of the air so that it doesn’t get bogged down and deposit wet lint in the ducts, which can clog the inside of the pipe. However, you need to use a booster fan that’s specifically designed for dryer ducts; moisture and lint will quickly ruin a conventional exhaust fan.

Misconception No. 4: If it’s really difficult to find a way to vent the dryer to the outside, an acceptable alternative is to vent it directly into the crawl space.

DO NOT vent a dryer directly into a crawl space or basement. I know I’m being repetitious, but I received so many similar questions about this that it obviously bears repeating. You’ll be pumping a lot of warm, moist air under the house that can cause both mold and structural issues, and you’ll also be letting all the lint accumulate, which is a definite fire hazard!

Misconception No. 5: It’s OK to use that white, corrugated plastic, flex hose to vent the dryer.

I wish I could tell you yes, because I know how easy that stuff is to use. But the answer is no. The white plastic flex duct has lots of problems. Wet lint accumulates in all the little folds, and can’t be removed through normal cleaning. The plastic has virtually no structural strength, so as the wet lint accumulates, the duct sags more and more, which allows more and more lint to accumulate in a vicious cycle. Over time, the duct simply fills up, less and less air can pass through it, your clothes take longer to dry, and eventually your dryer overloads and burns out — or worse yet, a house fire starts.

For dryer venting, use 4-inch smooth wall aluminum pipe. Where changes of direction are required, use 4-inch aluminum elbows. Hang the pipe from the floor joists — don’t let it drape on the ground.

Misconception No. 6: Dryer vents don’t need to be insulated.

If the duct is in a heated space, such as the inside of the house or in a finished basement, then no, it doesn’t need to be insulated. But if it’s running through a crawl space, unheated basement, attic or other unconditioned space where there’s the potential for freezing, then it does need to be insulated. Insulation helps prevent the moisture in the exhaust air from freezing inside the pipe, which would later lead to condensation and potential moisture problems when the pipe warms up and the ice melts.

Misconception No. 7: Dryer vents don’t need cleaning.

Your dryer only has the power to push that heavy, wet lint so far, so it’s inevitable that some of it is going remain behind in the vent pipe. As I mentioned before, a buildup of lint in the vent reduces the air flow and affects your dryer’s performance, so it should be professionally cleaned out periodically. How often is a matter of how much use your dryer gets. Large families that do lots of laundry should consider having it cleaned every six months, while someone living alone and doing laundry once a week or so might need to have it done only once in three or four years.

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