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posted: 10/11/2013 12:41 AM

Plastic dryer vents pose several potential problems

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Q. My handyman did some repair work under the house, and he said I have the wrong kind of exhaust duct for my clothes dryer. It's made of white plastic and looks like a long accordion. The dryer has been venting perfectly for more than ten years, so I can't see any reason to spend money replacing it. In your opinion, what is wrong with this kind of dryer duct?

A. Corrugated plastic ducts are often used to vent the exhaust from a clothes dryer, but there are three things wrong with this type of dryer duct:

• Exhaust from a clothes dryer can be very hot, especially if you have a gas dryer. Repeated heat exposure to paper-thin plastic can be a significant fire hazard. If a fire were to begin under your house, it could spread very quickly throughout the home. Therefore, a dryer vent duct should be made of noncombustible material.

• Plastic dryer ducts become brittle after years of use. Eventually, they crack and fall apart. Then, all of the clothes dryer exhaust vents into the crawl space, and since no one is likely to notice the damaged duct, this could go on for years, with lint build up occurring daily and moisture condensation occurring whenever the weather is cold. Dryer lint is highly combustible, which again, raises the issue of a fire hazard. Moisture condensation under the house can cause fungus infection on wood members and can promote the growth of mold.

• Corrugated dryer exhaust ducts, whether they are plastic or metal, tend to collect lint. As lint accumulates, the inside dimension of the duct becomes smaller, and this creates resistance to airflow, causing the clothes dryer to overheat. Once again, we have a fire hazard due to a substandard vent duct.

The solution is to install a 4-inch diameter, smooth, sheet metal exhaust duct that terminates on the outside of the building. The fittings should be secured with tape rather than screws because screws on the inside of a dryer duct can collect lint. The maximum permissible length of the duct is 14 feet with a maximum of two 90-degree turns. For each additional turn, two feet should be subtracted from the overall length. If greater length is needed to reach the outside of the building, a booster blower should be added to the duct.

Q. I'm planning to replace my old windows with dual-pane windows and am wondering if I should install them myself. Half the price of a contractor installation is for labor. I've read the installation instructions from the window manufacturer; it doesn't seem too complicated, and I'm very handy. Do you think this is a good idea?

A. Installation of dual-pane replacement windows is not too difficult for a handyman with reasonable mechanical skills. However, keep in mind that any deviation from the manufacturer's installation instructions could void the warranty. So if you install them yourself, be sure to stick to the specifications, and take plenty of photos along the way to document your compliance with the specified procedures.

• To write to Barry Stone, visit him on the web at, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.

Action Coast Publishing

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