Tips for Venting Clothes Dryer

<i> Special to The Times</i>

QUESTION: What is the recommendation for venting clothes dryers? I know it’s important to exhaust the moisture from the home, but I wonder if I can use a long exhaust pipe. My dryer is quite a distance from an outside wall.

ANSWER: You’ve tackled the most important part of the clothes dryer installation--the exhaust system. All dryers, gas and electric, should vent to the outside. This ensures that lint and moisture get out of the house, minimizing fire hazards from lint build up and air quality and moisture problems.

The general rule of thumb is to use as short and straight a section of smooth metal ducting as possible. (Flexing vinyl ducting, not smooth metal, is commonly used. It is less preferable, because of the rough interior surface.) The ducting is typically four inches in diameter. Most clothes dryer manufacturers recommend a duct run of no more than eight feet. Consider relocating the dryer next to an outside wall. The Uniform Mechanical Code offers the following specific guidelines:

Use smooth metal interior surface ductwork. The smooth surface is important because it minimizes the opportunity for lint to be trapped on rough surfaces on its way out. Lint buildup can reduce dryer efficiency and pose a fire hazard.


Ducts should not be put together with sheet metal screws or other fasteners that protrude into the duct as they might accumulate lint.

Flex duct is rough on the inside and can trap lint. It can also be crushed if the dryer is moved. The code allows flexible duct if the length is no longer than six feet and not enclosed in part of the building such as a wall, ceiling or under-floor.

Total duct length for your dryer exhaust should be no more than 14 feet, including two 90 degree bends. Additional bends will reduce maximum length by two feet per bend. Long runs with lots of bends severely restrict flow of exhaust.

Ducts should terminate outside the house with a back-draft damper or vent hood that blocks air infiltration. Vent hoods seal tightly when the dryer is not operating. This prevents unwanted hot or cold air from entering the house.

Dryers are one of the bigger energy users in the home. Installing a good exhaust system will help it run efficiently and keep it safe. If you’re in the market for a new dryer, look for models with an automatic shut off. It senses dryness and will shut off the dryer when the clothes are done.

Don’t over-dry clothes. Take them out while they’re still slightly damp and hang them. This reduces the need for ironing. Remember to clean the dryer filter after each use. And, in good weather, string up your clothes and put your solar dryer to work.

Written by Cynthia Putnam from the Education and Information Network of the Washington State Energy Office.