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Welcome to our blog!
We want you to be an informed homebuyer, and each blog post is a question that we have answered for our friends and customers over the years. Hope they help you make a good choice for your next home.

While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
©2015 - McGarry and Madsen Inspection.

Here’s a few signs of a clogged or damaged dryer vent that you will alert you to a problem:

  1. Excess lint behind the dryer.

  2. Overheat sensor shuts off dryer.

  3. Moldy smell in dryer.

  4. Longer drying time than usual.

  5. Dryer termination louvers that don’t open or barely open when the dryer is running.

  6. Visible lint ball behind louvers at termination. This is a frequent problem at homes where the dryer runs vertically to the roof then turns at a right angle for the air to exit through the termination louvers, and we see it when walking the roof. Because the termination is on the roof, it is not regularly checked by the homeowner.

And here’s what we check at the vent duct:

  1. Duct should be a stiff metal (minimum 0.016 inch thick) with a smooth interior surface. Ribbed ducts are no longer acceptable and are noted as a safety defect.

  2. Connections of duct sections cannot be made with sheet metal screws that stick into the duct.

  3. The maximum length of a straight duct is 25 feet, with a 5 foot reduction for each 90-degree bend and a 2.5 foot reduction for each 45-degree bend. The 25-foot length restriction does not include the transition duct.

   And, last, the duct termination:

  1. Ducts must terminate at the exterior of the home, not in an attic, crawl space, or—worst of all—interior wall. A clothes dryer can exhaust as much as a gallon of water as vapor that will condense on the surfaces of an enclosed space and lead to mold infestation. Many mobile home manufacturers put a sticker at the dryer location in the laundry like the one above, because termination under a home is such a problem.

  2. The termination should have a backdraft damper, typically a set of louvers that open under hot air flow, and should not have any type of screen in place.

  3. Dryer vent should not terminate within three feet of any door or window openings into the home. Also, although it is not mentioned in the building code, locating a dryer vent termination directly behind an air conditioning condenser is problematic because the escaping lint collects on the condenser coils and eventually clogs them.

   The building code defers to the dryer and vent manufacturers regarding length and size of ducts, so exceptions to some of the standards may be allowed per manufacturer. For more information on dryer vent sizing, see our blog post “What is the maximum length for a clothes dryer vent?”

   Maintenance and regular cleaning of the lint at the filter screen at the dryer and the duct interior is also important. The Consumer Products Safety Commission provides fire prevention guidelines for dryer maintenance in their fact sheet below.


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