The Importance of Bathroom Exhaust Fans

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Bathroom exhaust fans are crucial in preventing moisture buildup and mold growth. Manuel Breva Colmeiro/Getty Images

If you have ever used a bathroom without a functioning fan or window, you know how unpleasant it can be. Unpleasant odors can remain for a long time, whether from cleaning products or other sources.

However, the real problem is moisture. Humidity from showers creates fog on mirrors and penetrates walls. The warm air cools and turns into water, which gets trapped in the walls.

“Indoor condensation can lead to mold growth,” says Dave Bayne, CEO and owner of A1 Mold Testing & Remediation. “Moisture can seep into the drywall and create fungal growth,” often in hidden areas.

The Centers for Disease Control and Prevention warns that prolonged exposure to mold can cause allergies, coughing, skin irritation, and other health problems.

Excessive moisture can cause peeling paint and wallpaper, warped doors, and rusted fixtures. It also promotes bacterial growth.

Turning on the bathroom fan can help minimize these problems. “You should turn the fan on each time you run water in the bathroom and leave it running for about 20 minutes after you open the [bathroom] door,” says Bayne. This is especially important after taking a shower. If you frequently forget to turn the fan off, consider installing a fan timer. Also, remember to clean the fan at least once a year.

If you are a homeowner, make sure that your fan is vented directly to the exterior of the house through insulated ducting. “Building codes today require that the exhaust is vented outside through insulated ducting to a roof vent that goes directly to the exterior,” says Bayne. Otherwise, you may be contributing to moisture and mold problems in your attic or walls.

If you don’t have a bathroom fan, check your local building codes to see if an operable window is required for adequate ventilation.

Now That’s Interesting

Bathroom fans are rated by sones, not decibels. A 1-sone fan is about as loud as an average refrigerator, while a 5-sone fan is as loud as a jet aircraft. If your fan is too loud, consider purchasing a quieter model that still provides adequate ventilation.

Originally Published: Jun 24, 2019

Frequently Asked Questions about Bathroom Exhaust Fans

Why is a bathroom fan necessary?

A bathroom fan is crucial as it helps to remove moisture from the bathroom. It also eliminates unpleasant odors and keeps the restroom clean, ensuring a comfortable environment.

How long should the bathroom fan be in operation?

As soon as you turn on the shower or bath water, you should switch on the fan. Furthermore, it is recommended that the fan be left on for approximately 20 minutes after bathing is complete to prevent the accumulation of moisture and mold in the bathroom.

Is it difficult to replace a bathroom exhaust fan?

Replacing a bathroom exhaust fan is a relatively simple process that does not require a lot of effort. You can use the existing connections and wires to install a new fan. When purchasing a new fan, be sure to select one that is the same size as the one you are replacing to avoid making adjustments to the ceiling hole. To avoid mistakes, it is essential to use switch wires and connect the new wires by hand.

How do you choose the right size bathroom fan?

Bathroom fans are rated according to the airflow in CFM (cubic feet per minute). If your bathroom is less than 100 square feet, the general rule is to have at least 1 CFM per square foot of room area. This means that a bathroom that is 60 square feet in size would need a 60 CFM fan. For bathrooms larger than 100 square feet, add up the CFMs associated with each fixture to determine the appropriate fan size to purchase.


1. What is a bathroom exhaust fan?

A bathroom exhaust fan is a device installed in a bathroom ceiling or wall that helps to remove moisture and unpleasant odors from the bathroom. It works by drawing out the air from the bathroom and venting it outside of the house. Some exhaust fans come with a light or a heater as well.

2. Why do I need a bathroom exhaust fan?

You need a bathroom exhaust fan to prevent moisture buildup, which can lead to mold and mildew growth. It also helps to remove unpleasant odors from the bathroom, making it more comfortable to use. In addition, exhaust fans can help to improve the air quality in your home by removing pollutants and allergens.

3. How often should I use my bathroom exhaust fan?

You should use your bathroom exhaust fan every time you take a shower or a bath, and for at least 20 minutes afterwards. This will help to remove moisture from the bathroom and prevent mold and mildew growth. You may also want to use the exhaust fan when using cleaning products or hair styling products that can release fumes.

4. Can I install a bathroom exhaust fan myself?

If you have experience with electrical work and carpentry, you may be able to install a bathroom exhaust fan yourself. However, if you are not comfortable working with electricity or cutting holes in your ceiling or wall, it is best to hire a professional to install the fan for you.

5. How do I choose the right size exhaust fan for my bathroom?

The size of the exhaust fan you need depends on the size of your bathroom. A general rule of thumb is to choose a fan that can move at least 1 cubic foot of air per minute (CFM) per square foot of bathroom area. So, for example, if your bathroom is 100 square feet, you would need a fan with a CFM rating of at least 100.

6. How do I maintain my bathroom exhaust fan?

To maintain your bathroom exhaust fan, you should clean the fan cover and the fan blades regularly to prevent dust and dirt buildup. You may also need to replace the fan filter or clean the fan motor if it becomes clogged with debris. It is a good idea to have your exhaust fan inspected by a professional every few years to ensure that it is working properly.

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