Q: My clothes dryer outdoor vent flapper makes a vibrating noise when it's windy. It probably doesn't seal well and lets a lot of cold air blow indoors through my dryer. What can I do to improve the vent?
A: A clothes dryer is a major energy consumer, and a leaky outdoor vent cover is a significant contributor. A poor-sealing vent cover can also let insects, rodents and allergy-causing particles indoors. I had a small snake crawl in through my old leaky dryer vent cover.
Even though you may not feel a draft, a leaky vent cover lets cold outdoor air blow into your house when the dryer is off. In cold climates, I have actually heard reports of damp clothes freezing in a dryer overnight. The energy loss is just as great in the summer with warm and humid air leaking in a poor-sealing vent cover.
First, check your outdoor dryer vent cover to make sure it is closing tightly. The hinge point can often become clogged with lint and the flapper may not swing closed freely. Just a small gap around the flapper can push up your utility bills.
After you clean it, check the fit. Most dryer vent outlets installed by builders don't seal well when they are new. You can often hear the cover vibrating open and closed on a windy day. This indicates a poor seal.
Don't try to modify it by adding any weight to the cover flapper. This may increase the opening resistance too much and impede the necessary air flow through your dryer. The efficiency of your dryer may be reduced and it may result in expensive repairs.
There is an inexpensive energy-efficient dryer vent cover that uses a different design from the standard flapper-type cover. It incorporates a vertically "floating cap" that moves up when the dryer is on and blowing against it. There is a counter-balance spring inside to ensure it opens freely for maximum dryer efficiency.
Because there is no hinge, this eliminates the common sticking-hinge problem with flapper covers. When the dryer is off, the cap slides back down and seals tightly over the end of the dryer duct outlet. No air can leak in or out. It is made of durable plastic and you can paint it to match your house.
You can easily install any dryer vent outlet yourself in about 15 minutes. Be sure to caulk around the duct and the outside wall opening. Otherwise, air may leak inside the wall and blow out indoors through electrical outlets.
Q: The duct from our bathroom vent fan runs directly into the attic and opens about one foot above the insulation. Should I continue the duct to an outside attic wall?
A: You should extend the bathroom vent duct to an outside attic wall. Even properly sized attic vents will not be adequate to exhaust the tremendous amount of moisture from several consecutive showers.
With the high level of humidity in your attic area, it can condense, even in only moderately cold winter weather. This may cause dampness in the insulation, reducing its insulation value, or possibly damage to the lumber in the attic.
Questions should be addressed to James Dulley, c/o Baltimore Sun, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.