Asked by: Lauryn Querol
home and garden indoor environmental quality

Why does my bathroom exhaust fan drip?

Last Updated: 25th March, 2020

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Many people notice the issue when the bathroom exhaust fan starts dripping on their head as they step out after a shower. The usual cause is condensation inside the duct. In winter, when the warm moist air from the bathroom hits cool air in the attic or outdoors, it condenses, sending drips back down the ductwork.

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Regarding this, how do I stop condensation in my bathroom fan?

How To Prevent Ceiling Stains Around Your Bathroom Exhaust Fan

  1. Use an insulated duct inside the attic. This is a no-brainer.
  2. Use the shortest run possible. The longer the bath fan duct, the greater the potential for condensation inside the duct.
  3. Make sure the duct is tightly connected to a roof cap with a damper.
  4. Check the damper at the roof cap periodically.

Similarly, is it bad to oversize a bathroom exhaust fan? Bathroom vent fans are rated for the amount of air they can move, measured in cubic feet per minute, or CFM. First, it's a good idea to oversize the fan slightly. In our sample 54-square-foot, for example, it's a good idea to install a 60 CFM fan for good measure.

Keeping this in consideration, how long should you run a bathroom exhaust fan?

According to the Ask the Electrician Web site, a bathroom fan should be left running for at least 20 minutes after a person gets out of the shower. This will ensure that all of the humidity is cleared out of both the room and the ventilation ductwork.

How do you insulate a bathroom exhaust fan?

The exhaust fan housing should be covered with an insulated, airtight box. The box can be made from rigid foam. The seams can be taped with housewrap tape. Caulk or spray foam can be used to seal the box to the ceiling drywall and to seal around the exhaust pipe.

Related Question Answers

Tracy Ougier

Professional

What is maximum duct length for bathroom exhaust fan?

ft. bathroom and 70 ft. of duct (equivalent length), you'll need a 110 cfm fan to achive the recommended 8 air changes per hour.

Juanita Maihofer

Professional

Can I use flex duct for bathroom fan?

Can Flexible Duct and Air Connector be used for bathroom/shower exhaust fans? Yes. We recommend that you use insulated flex duct in longer vent run applications to assist in keeping the humidity from condensing inside the duct and to help prevent the pooling of water, which can damage the core. Yes.

Argia Benick

Professional

Should I use insulated duct for bathroom fan?

Insulate the bathroom exhaust vent fan ducts: In un-conditioned space such as an attic, where otherwise your fan duct will be exposed to cold attic air in winter, use insulated solid metal ducting or insulated flex duct. Watch out: we do not recommend purchasing vent ducts with insulation on the duct interior.

Matha Ezquer

Explainer

Do you need to vent a bathroom fan?

Bathroom vent fans must be vented to the out of doors. Venting this fan into the attic is simply asking for problems. The excessive moisture will cause condensation on the roof members, insulation and eventually cause mold. It is never OK to vent directly into an attic even if the attic itself is vented.

Quino Purcel

Explainer

Can you vent a bathroom fan through a wall?

If the soffit is unvented, venting the bath fan through it is possible, but be aware that the moisture the fan exhausts can cause mold to form on the soffit board and stain it. Running any duct through an outside wall should not be done because it will get cold, which would cause condensation.

Yuhao Gironda

Pundit

Is it OK to leave bathroom fan on?

You should run the fan for about 20 minutes during and after a bath or shower. You should not, however, leave the fan on 24/7. If you run the fan constantly the ball bearings inside will lock up. This can cause the motor to overheat, which can, in turn, cause a fire.

Martynas Schroers

Pundit

Where do you vent a bathroom fan?

The fan exhaust must vent directly to the exterior of the home. Do not put the vent termination in a roof overhang or soffit. Don't put it on a wall near or under a roof overhang. The moist air that's belched out by the fan can be sucked right up into the open soffit vents and be drawn into your attic.

Sherron O'Rourke

Pundit

What is the difference between ventilation fan and exhaust fan?

The difference between an exhaust fan and a fresh air fan lies in their application. Whereas an exhaust fan helps in throwing out the air that is inside the house or the area that it is placed in, fresh air fan brings in fresh air from outside, into the area where it is placed.

Laveta Agafonoff

Pundit

Do bathroom exhaust fans really work?

If the fan holds up the toilet paper, then the fan is working properly. Keeping the bathroom door open while running the fan will allow for air exchange from other parts of the home. We recommend using bathroom exhaust fans for 15 minutes after using the shower to help move humid air out of the living space.

Guenther Malone

Pundit

Can you leave a bathroom fan on all night?

Experts say bathroom fans can become overheated when clogged by lint and dust, when left on too long or because of simple failure. Run the fan for only short periods, and never leave it on overnight or while no one is home.

Latrice Lindheim

Teacher

Can bathroom exhaust fans cause fires?

Bathroom exhaust fan lint is a FIRE HAZARD! However, they can also present a potential fire hazard if not cleaned and maintained on a regular basis. Fans, over time build up lint which can cause the motor to overheat and ignite the lint, plastic fan blades and the nearby combustible wood structure.

Urcesino Raghuram

Teacher

How long can a fan run continuously?

When you set your fan to “ON,” you're telling it to keep running 24 hours a day, 7 days a week, regardless of the heating or cooling setting.

Osazuwa Guzman

Teacher

What does the bathroom vent do?

A bathroom vent fan is a mechanical ventilation device that exhausts indoor air to the outdoors via a flexible tube or metal duct. A vent fan will draw out moisture and odors from the bathroom, improving air quality. Even when not required, though, a vent fan is a good addition to any bathroom.

Cesaria IƱiguez

Teacher

What CFM bathroom fan do I need?

Ventilation rates based upon eight air changes per hour are generally suggested. For most bathrooms this works out to one CFM per square foot of bathroom area. For example, a 7' x 10' bathroom would require a 70 CFM fan. A 50 CFM rating is recommended as a minimum for bathrooms 50 sq.

Elen Verhees

Reviewer

What is the highest CFM bathroom fan?

Add the Broan(R) 434 CFM High-Capacity Ventilation Fan to your bathroom to ventilate your air and help prevent mildew. The fan features 2.3 sones for quiet operation and vents moisture in bathrooms up to 390 sq. ft.

Daylos Masustegi

Reviewer

What does 2 Sones sound like?

The thing to consider with sones is that 2 sones is twice as loud as 1 sone, 4 sones is twice as loud as 2 sones and so forth. In exhaust fans choosing a fan with a sound rating at or below 1 sone will be very quiet. 1 to 2 sones will be heard and anything over 2.5 sones will be noticeable.

Vern Gali

Reviewer

Is more CFM better bathroom fan?

A fan's ability to move air is measured in cubic feet per minute (CFM). The bigger your bathroom, the higher the CFM rating you'll need. A fan should have a CFM rating high enough to replace the air in your bathroom at a rate 8 times per hour. If all else fails, check the packaging.

Vivek Gritzner

Reviewer

How much air should a bathroom exhaust fan move?

A typical bath fan is rated to move 50 cubic feet per minute of air when it's operating, but most actually move about half of their rated air flow.

Roxie Mehden

Supporter

How many Sones is a quiet bathroom fan?

One sone is equivalent to the sound of a quiet refrigerator. A quiet bathroom fan will be rated at about 1.5 sones or less.