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Bathroom Exhaust Fans

DEAR TIM: I have several inexpensive builder-grade exhaust fans in my home. They are noisy, and I don't feel they do a good job of getting rid of the moist air produced while showering. Is it possible to get high-performance ventilation with little or no noise? I would like a bathroom exhaust fan with a light. Can you tell me how to install a bathroom fan so I do not cause any damage to my home? Faith F., Mt. Crawford, VA

DEAR FAITH: Bathroom fans are a critical part of a home-ventilation system. A bathroom exhaust fan, improperly installed, can create all sorts of hidden damage to a home. All too often, installers just let the moist air escape into an attic space. This moist air can condense on the cooler surfaces in the attic. This liquid water on the wood surfaces creates mold and can lead to serious wood rot.

The good news for you is that the exact fan you are looking for is available. It has been around for years, but many builders choose to install cheaper fans to try to make their houses more affordable. The trouble is, I have discovered many consumers would gladly pay a slight upcharge if they were given the option of having great ventilation and less noise while in the bathroom. It is my hope that builders start to learn to offer home buyers more choices. But I feel that day may never come, as builders will argue that more choices equate to more problems.

This fan may look like an overweight flying saucer, but rest assured it does a fantastic job of vacuuming moist air from bathrooms. PHOTO CREDIT: Tim Carter

This fan may look like an overweight flying saucer, but rest assured it does a fantastic job of vacuuming moist air from bathrooms. PHOTO CREDIT: Tim Carter

I have had fantastic luck installing bathroom exhaust fans that are actually located in the attic space. They resemble central vacuum systems inasmuch as the fan motor is located perhaps 8 or 10 feet away from the bathroom. Most builder-grade fan motors are just inches away from the bathroom ceiling. This is one reason why they are so noisy.

These remote bathroom exhaust fans have insulated flexible duct pipe that extends from the fan motor to small exhaust inlet boxes that are attached to the framing members in your bathroom ceiling. The box extends up into your attic, and all you see on the bathroom ceiling is a sleek round inlet cover. The powerful fans can slurp up massive amounts of moist humid air that rises to the ceilings as you shower. This air is ducted through the roof of your home in a special roof vent cap that is easy to install.

I have found that it is often best to vent fans and dryers through the roof. I urge you to watch this video of mine to see how easy it is to install the correct vent-cap flashing on a roof. Have no fear - if done right you will have no leaks.

The flexible insulated ducting that extends from the roof to the fan, and then to your bathroom ceiling, does two important job: It helps to suppress noise from the fan, and the insulation prevents condensation from forming inside the flexible piping. Many people complain about a leaking bathroom fan, when in fact the water is not a roof leak but condensate water that forms inside of uninsulated exhaust piping and flows down the piping into the bathroom.

The bathroom exhaust fans I use come with or without lights. The ones with lights use brilliant compact halogen bulbs that fit into the center of the small circular vent covers. I always place two of these inlets with lights in each bathroom, one immediately adjacent to the shower area and the other toward the center of the bathroom. These lights produce good overall lighting for the average bathroom. You will need additional lighting above any mirror.

To avoid damage to your home while installing a bathroom fan, always follow the written instructions that come with the fan. If you are not comfortable working with high-voltage electric wire so it will pass inspection, then hire a competent electrician to connect the fan. The most important aspect is to duct the air from the bathroom to the exterior of the house. You should do this through the roof.

Avoid the temptation of venting your fan through the horizontal soffit that can be found in many roof overhangs. All too often the moist air billows up under the soffit and is sucked into the attic. If this happens, mildew and wood rot is a certainty.

Problems with bathroom exhaust fans can happen years later. The connections between the flexible duct pipe, the fan, inlet boxes and the roof vent cap must be permanent. Never rely on duct tape to secure these connections. The high heat and humidity in attics can cause duct tape to fail. It is better to use metal band clamps that are nearly identical to traditional automotive radiator hose clamps. These inexpensive clamps can be found at hardware stores, ductwork shops and some home centers. Once the band clamp is connected, then use tape as directed by the fan manufacturer.

Be sure there are no kinks in the flexible duct pipe. Also be sure to install a makeup air duct in your home that allows an equal amount of fresh air to enter your home for every bit of air the exhaust fan is expelling. If you do not have this critical makeup air, you could cause "backdrafting" to occur. This means poisonous gases are drawn into your home through furnace or water heater exhaust pipes.

Column 665

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12 Responses to Bathroom Exhaust Fans

  1. Both my bathroom exhaust fans leak water and ruin the ceiling. They are each vented separately and appear to be adequately insulated. It only leaks during the cold winter months so it is condensation that is causing but how can it be stopped?

  2. I have had the best luck with a switch i bought that monitors the moisture/ condensation in the bathroom and automatically turns on my exhaust fan. The switch is called DewStop, I like it because nobody has to turn it on or off. My kids didnt remember to turn on the timer switch, with this I dont have to worry. It can be operated manually also. My fan wasn't the problem... it was getting it turned on that was the problem. Problem solved!

  3. Tim -- I like the remote fan options. I would like it to serve up to 3 bathrooms -- 2 of which have a shower. What is the most effective way to switch/operate the fan? Is it simply a 3-way switch? Or is there a standard way to allow any of the 3 locations to turn the fan on and keep it on for a long enough time?

    Thanks!

    Karl

  4. I was wondering, can I use 3 inch black ABS pipe to vent fan outside instead of the plastic type flex tubing?

  5. I have 2 bathroom fans that I need to vent into one vent cap. I have the ducts and a wye connection. Do I need some sort of baffle system to maintain proper pressure so I dont simply push the air from one bathroom to the other? The local big boxes dont seem to carry anythng like that. Any thoughts?

  6. Do you have a preference on roof vent caps? I am looking for one with screen to keep out birds, backdraft damper that will not clank open and shut on windy days.

  7. Looks like there are bits of shredded, brown leaves hanging down from our bathroom exhaust fan. What do you think is causing this? Thanks:)

  8. I tripped a breaker somewhere in my house while trying to plug in a George Foreman Grill. Now both exhaust fans in my bathrooms no longer come on. I looked at the breaker box and everything is in the right position. How do I get these back on?

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