Home inspector: Problems with clothes dryer vent

Q. When we bought our condo, the home inspector said we might have trouble with the dryer vent, and he sure was right. The laundry is located in the middle of our home, in a hall closet; so the dryer has to vent vertically, up through the roof. This causes two problems: The vent becomes clogged with lint, and moisture in the duct causes the ceiling to become wet. Can anything be done to correct this problem?

A. A vertical dryer vent is typically a problem because it acts as a moisture condenser. The sheet metal duct is cooled by the outside air in the attic. This causes the steam from your dryer to become liquid on the inner surface of the duct. This wetness trickles down and may leak at duct fittings, causing wetness and possible mold on affected materials (such as your ceiling). Moisture in the duct also tends to collect lint, which forms an increasingly thick layer on the vent surface, thereby reducing the efficiency of your dryer.

The problem begins by placing the laundry facility in an impractical location in the building. It the dryer had been located near an exterior wall, it would have been simple to vent it horizontally through the wall. When a laundry is situated near the center of a home, especially if there is a slab foundation, a vertical duct is often the only option for ventilation.

Unfortunately, a horizontal vent duct is not required by code. If it were, architects and builders would be more practical in their placement of laundry facilities.

One solution, in your case, would be to relocate the laundry to a more sensible location, depending on the layout of your floor plan. Otherwise, the duct should be modified or replaced with one that has no fittings where leakage is likely to occur. Periodic servicing of the vent duct will be needed to remove accumulated lint.

Q. I plan to be traveling this winter and want to winterize my home. Some friends have recommended draining my water heater and turning off the gas. Others say this is not a good idea. What is your opinion?

A. It is not a good idea to turn off a water heater completely. When a water heater becomes cold, all of its constituent parts shrink. When you relight the burner at a later date, re-expansion of the fixture can cause leaking at the fittings, and replacement of the unit might then be necessary. The recommended procedure when you leave home in winter is to turn the water heater thermostat to the “vacation” setting. The pilot light remains lit, maintaining a slightly warm water temperature within the fixture until you return home.

If your home is heated with gas, it is also wise to leave the gas service on when you are away. If the temperature drops below freezing, lack of heat can allow freezing water to split your pipes, and this can cause major damage to the building and its contents. Instead, you should turn the thermostat to the lowest setting, usually around 50 degrees.

Ÿ Email questions to Barry Stone through his website, housedetective.com, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.

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