Bath Ventilation Tips - Choosing a Bathroom Exhaust Fan

With any remodeling project, you'll have to make several important decisions both from a design standpoint as well as a functional one. For example, if you're remodeling your bathroom, some decisions will be more exciting than others, like choosing the perfect stone slab for your vanity top.

Other decisions are a bit less exciting and typically have to deal with pure functionality, like selecting the right bathroom exhaust fan. While your vanity top is an element that you'll look at every time you use the bathroom, choosing the right bathroom exhaust fan is a decision that, while it may not be an element you look at or even think about, the wrong choice can make your bathroom practically unusable.

If you choose an exhaust fan that can't properly handle moisture, you run the risk of developing a mold or mildew problem, and over time, even rot... plus, it may not effectively remove odors, which is never fun! So, while the look of your bathroom vanity is certainly important, sometimes it's the behind the scene decisions that can make a major difference in the functionality, comfort, and enjoyment of your bathroom.

In this post, we're going to share some tips to teach you what to look for in a quality bathroom exhaust fan and how to choose the right model for your bathroom remodeling.

Four Considerations When Choosing A Bathroom Exhaust Fan

There's nothing quite as relaxing after a hard day than taking a long luxurious hot shower. But the steam and humidity that comes with these showers can be wreaking havoc on your air quality unless you've included a properly sized bathroom exhaust fan in your remodel.

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Bathroom fans are typically installed in the wall or ceiling and are designed to add ventilation, improve airflow, reduce excess humidity, and remove odors. Technically, they are connected to your home's ductwork and use it to remove the warm moist air from your bathroom, exhausting it outdoors.

The proper bathroom exhaust fan helps prevent mold and mildew problems and keep you safe and comfortable by maintaining healthier indoor air quality. Here are four things to consider when shopping for your bathroom exhaust fan.

Bathroom Exhaust Fan Installation

Most bathroom exhaust fans are ceiling installs. However, some models can also be installed on a wall. Your venting should be integrated with your home's ducting system to take the warm moist air outside your home. Venting into an attic only transfers that warm moist air to another area where problems can occur. Consider installing a fan/light combo to replace an overhead light for easier wiring. If you're installing your bathroom exhaust fan directly over the shower/tub, make sure that it is safety rated for this type of installation.

Consider These Bathroom Fan Features

Today, bathroom exhaust fans have several different features that make them more efficient and add to your comfort. Features can include:

Integrated lighting: Many different models integrate lighting into the unit. They can either replace existing lights or supplement your lighting design. Some include night lights for a non-disruptive late-night bathroom experience.

Built-In Heaters: Fans with built-in heaters add extra warmth on those cold winter mornings.

Humidity and Motion Sensors: These features improve a fan's overall efficiency and help you conserve energy. A humidity sensor monitors your bathroom and turns on the fan when the humidity reaches a pre-determined threshold and turns it off when the humidity is reduced. A motion sensor will automatically turn lights on and off when someone enters or leaves.

Control: Bathroom exhaust fans that have multiple functions include separate controls for each feature. You can use them individually or all together. With many units, you'll not only receive a separate wall switch for control, but you may also receive a wireless remote.

Noise Levels

If your bathroom fan sounds like a jet engine or a race car, you're probably not going to enjoy a relaxing bathroom experience. When shopping for fans, always consider noise level and choose the quietest fan you can afford.

Bathroom exhaust fans are rated using a measurement called “sones.” A sone is a measurement that relates to how the average listener hears a sound. For example, the quiet hum of a refrigerator is rated at one sone. Each additional sone doubles the sound level, so two sones would be double the volume.

A quiet bathroom fan operated at a sone rating of two or under. Fans with a rating of three of four sones will generate increased white noise. Stay away from fans rated a five or higher.

Ventilation Efficiency

Today, as we're all working hard to lower our environmental impact, efficiency should be top of mind when shopping for any home appliances or systems. Fortunately, bathroom exhaust fans are more efficient than ever before.

An Energy Star rated bathroom fan typically uses 70% less energy than conventional non-Energy Star models. This keeps your energy costs and uses low.  Energy Star models must meet the qualifications for low noise, low wattage consumption, and powerful performance under static pressure.

To get the most bang for the buck, choose an Energy Star rated bathroom exhaust fan. To make it even more efficient, choose a model with a moisture and motion sensor, so it runs only when needed.

Sizing Your Bathroom Exhaust Fan

This is THE major consideration when choosing your fan. Installing the wrong sized fan can result in serious problems down the road. Your bathroom exhaust fan is responsible for venting moisture and odors from your bathroom. If your unit is too small, it can contribute to the growth of mold and mildew. In extreme cases, it can lead to a rotting subfloor, which can be extremely expensive to fix.

Bathroom exhaust fans are required by the National Electrical Code and local building codes for any bathroom that does not include a window, often even when windows are present. It's important to understand how to properly size your vent fan and choose the right one for your bathroom.

Bathroom fans are rated by the amount of air they can move in one minute. The measurement is CFM, which stands for cubic feet per minute. A good rule of thumb to follow is that you need 1 CFM per square foot of space in the room.

Square footage is determined by multiplying the room's length by its width. So a bathroom that is 10 feet long and 8 feet wide is 80 square feet. So when purchasing a fan, look for a model with a CFM rating of at least 80.

With that being said, here are a few things to consider when choosing the right bathroom fan for your project.

• It's a good idea to oversize the fan slightly. For example, our bathroom measures 80 Square feet, so look for a rated fan for 90 or 100 CFM.

• If your bathroom has a jetted tub or a separate water closet, you may want more than one fan for better coverage.

• The minimum allowable fan is rated for 50CFM, so if your bathroom is only 42 square feet, you'll still need a 50 CFM fan.

If you have a larger bathroom, say over 100 square feet, an alternative method for sizing your fan is the number of fixtures.

To use this formula, you must add up all of the CFM ratings for each fixture/ For example:

Bathtub 50 CFM
Jetted Tub 100 CFM
Shower 50 CFM
Toilet 50 CFM

So if your bathroom includes a soaking tub, shower, and toilet, you should install a fan with no less than a 150 CFM rating. If your soaking tub is jetted, add 50 CFM and look for a fan rated 200 CFM or higher.

If you have a separate alcove or room for the toilet, consider adding a separate second fan for this space.

When buying a bathroom exhaust fan, the bottom line is to consider the size you'll need and then consider any other features like integrated lights, heat, and sensors. Always consider the noise factor as well.

If you're still unsure what's best for you, your designer or design-build contractor can help you define your needs and choose the perfect bathroom exhaust fan for your project.

If you live in the greater Madison, Wisconsin area and are considering a bathroom remodeling project, give the award-winning design team at Degnan Design-Build-Remodel a call at (608) 846-5963.

Whether you're planning a powder room upgrade, a complete gut remodel of your en suite Master bathroom or converting the tub surround to a shower in the basement in-law suite. We can help! Call today for a free no-obligation consultation to discuss your project.

This article was updated by Abe Degnan on 9/12/2022.