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  • Writer's pictureSquare One Inspections

Dryer Vent Ducts

Clothes dryer fires are both more common than most people realize, and very easy to prevent. One of the more common deficiencies we find on home inspections are improper dryer vents.

According to the National Fire Protection Association, 17,000 home clothes dryer fires are reported each year, causing more than 50 deaths and $236 million dollars in property loss. Unsurprisingly, the leading cause is the accumulation of lint in the dryer vents. Additionally, a partially clogged vent duct will make your dryer much less efficient.

Look out for the signs of a significantly clogged dryer ventilation:

• A musty odor is noticed in the clothing following the drying cycle

• Drying cycles that take longer than expected, causing excessive heat in the clothes and/or the laundry room OR clothes that remain wet at the end of the cycle.

• The accumulation of lint on the dyer vent hood flap, possibly causing it to not open/close properly.

• Large amounts of lint build up in the lint trap each cycle

Fortunately, the vent duct can be cleaned easily by the homeowner, or professionally if needed.

There are several characteristics of a dryer duct that will help reduce the accumulation of lint, check with local codes for specifics in your neighborhood:

• Short, straight, runs of ducting are preferred.

• All dyer ducting must be a minimum of 4 inches in diameter; frictionless ducts (rigid metal or flexible aluminum) encourage air flow. Foil and vinyl are prohibited because the accordion style creates a significantly reduced internal dimension and multiple ridges to catch the lint.

• Flexible transition hose between the dryer and the wall outlet should be aluminum flexible duct, but the old foil duct is acceptable in tight spaces for very short runs. Never use plastic of vinyl. Occasionally monitor the transition duct behind your dryer to ensure it hasn’t been crushed.

• Concealed ducting must be rigid metal.

• Duct joints should be installed so the male end points in the direction of airflow.

• Joints should be secured with metal tape (not duct tape), do not use rivets or screws as these will encourage lint collection.

• The length of the ducting should not exceed 35 feet. Deduct 5 feet from the allowable length for every 90 degree elbow and 2.5 feet for every 45 degree fitting. These lengths may vary per local codes or dryer manufacturer’s recommendations.

• Termination of the venting must be to the exterior with a proper hood equipped with a backdraft damper.

Most homeowners have never given their dryer vent any thought. None of these recommendations are very expensive or difficult, usually well within the capabilities of most homeowners. There are professionals that can help clean and/or install proper vent ducts. The biggest tragedy of any dyer fire is that it was always preventable. So if you own a clothes dyer, we encourage you to take a look at the vent ducting and bring it up to spec so you don’t become the next statistic.

Matt Tycz is a Certified InterNACHI Home Inspector and co-owner of Square One Home Inspections, LLC in Brunswick, Maine.

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