Bathroom Exhaust Fans: A Homeowners Guide

September 2, 2023


This guide has everything you need to know about your bathroom exhaust fans.


Types and costs.

And resources that cover everything related to bathroom fans.

In other words:

It's a one-stop-shop for homeowners looking to understand, purchase, and install their bathroom fans. From safety to odor control, there are many reasons why having bathroom exhaust fans in your home are an essential necessity. 


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Chapter 1: Purpose and Benefits Chapter 2: Ventilation and Noise Considerations Chapter 3: Features of Bathroom Exhaust Fans Chapter 4: Installation: Common Problems and Fixes Chapter 5: Efficient Bathroom Exhaust Fans Chapter 6: Care and Maintenance of Fans


Chapter 1

Purpose and Benefits

The primary purpose for having an exhaust fan is to remove the moisture out of the bathroom. These fans help to control and eliminate bathroom odors.

Additionally, they add to the safety of the home and its residents by reducing fumes from cleaning agents that could potentially cause health-related issues. Bathroom exhaust fans will help improve the quality of indoor air.

Benefits of a Bathroom Exhaust Fan

1. Eliminate Odors 

One of the main reasons for having an exhaust fan is for odor control. If an unpleasant odor occurs in the bathroom, it can easily be drawn out with the help of an exhaust fan.

As a result, the ventilation system will enable you to keep your bathroom well maintained, while offering a clean atmosphere for the next person.

2. Humidity Reduction

Reducing the humidity in a bathroom is vital for its upkeep. Excessive moisture can wreak havoc on bathroom walls by causing paint and wallpaper to peel. In extreme cases, it can even cause doors to warp!

Most importantly, the humidity can cause mold to accumulate. These spores can grow rapidly and can be difficult to get rid of. Therefore, it is crucial to have bathroom exhaust fans to prevent this from happening.

3. Reduce Airborne Contaminants

Bathrooms are typically cleaned with aggressive chemicals, which can cause a variety of health issues when inhaled. This is a major concern especially for small children, the elderly, or those with current lung conditions.

Additionally, if the bathroom is already experiencing a mold problem, the fan will help to remove the buildup of spores in the air. This, in turn, will also help to slow down the mold's growth rate.

4. Help Eliminate Foggy Mirror Syndrome

Bathroom exhaust fans will help control the moisture and remove water vapor on your mirrors and walls.

Chapter 2

Ventilation and Noise Considerations

Ventilation Requirements (Based on Numbers)

The need for proper ventilation and air movement is a relevant consideration in bathroom exhaust fans.

Air movement is typically measured in cubic feet per minute (CFM), a standard measurement of fan airflow. HVI, Home Ventilating Institute, adds:

"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.

Here's a helpful chart HVI created to use as a guide for bathroom ventilation.

For bathrooms between 50 and 100 square feet, estimate 1 CFM per square foot of floor space. For smaller bathrooms (less than 50 sq. feet), 50 CFM. For larger than 100 square feet, you have to tally the CRM requirement for each bathroom fixture to estimate your needs. Add 50 CFM for each toilet, tub or shower. And 100 CFM for jetted tubs.

The bigger your bathroom, the higher the CFM rating you'll require. Home Depot compiled a simple formula to determine the size of your bathroom:

Length x Width x Height x 0.13 = Minimum CFM rating

Most fans will be rated from 50 to 110 CFM.  

Noise Level to Consider When Selecting Bathroom Fans

Sound levels in bathroom fans are rated in sones, not decibels. The sones rating is a measurement of how the sound is perceived by the listener.

The lower the rating number, the quieter the fan. 

Hear the difference between the 4+ sones versus 2 sones.

Bathroom Exhaust Fan Noise Comparison




The best exhaust fan will offer two important features: quietness and remove moisture and odors.

Use the formula to best calculate the fan sizing that is appropriate for your space. From there, you can determine a sone rating. It's always good to have a fan that sucks out the most air at a lower noise cost.

Tip: Cleaning your unit helps with noise reduction. (See chapter 6)

Chapter 3

Features of Bathroom Exhaust Fans

Exhaust fans can be selected on the basis of your own style and overall performance.

Bathroom fan features in today's market can include, fans with lights, humidity/moisture sensing, and heat lamps.

The combination fan and light is common. There are products that offer a line of recessed fan/lights that will look like standard recessed lights. The ceiling exhaust fan is easy to install.

Have you ever left the upstairs bathroom fan on all day?

You have a choice to add a timed fan. Installing timer switches can help reduce mold build-up without wasting energy. Conservation Mart recently updated a post on Bathroom Exhaust Fan Timers: Perfect Solution for Forgetful People. It's a great solution to getting the benefit of ventilation and working efficiently. 

In addition, there are moisture sensing switches to turn your fan on and off based on the humidity levels in the bathroom.

Your bathroom exhaust fan can be "smart". No need to have your fan run all day.

"A humidity sensor includes a manual fan switch, but if your sensor is set up correctly it should turn on and off based on the humidity in the room. With most sensors, you can also tell it how long it should run when it senses a certain level of humidity."

How to Install a Humidity Sensor in a Bathroom


Exhaust fans with heat lamps is also an option. Fan and heater can operate together or independently offering you ventilation and warmth if needed.

Chapter 4

Installation: Common Problems and Fixes 

Although most homes come with exhaust fans already installed, not all of them are effective.

In order to get the most out of your bathroom fan, it is important to install one that will provide all of the necessary functions.

Common Problems With Installation to Avoid

Although there are many reasons for using bathroom exhaust fans, many people often fail to do so. In most cases, this is because the fan is loud and annoying. This is a common problem which occurs when the fan is not properly installed.

Poor installation also frequently involves a lack of insulation, which can cause heat to escape into the attic. Fortunately, all of this can be avoided with the appropriate exhaust fan and the proper installation.

The key to ventilation and installation is to guarantee the air gets brought outside. Older homes that have it vented into the attic can experience mold from moisture collecting.

For the Do-It-Yourselfer's, our friends at Lowes show,

How to Install a Bathroom Exhaust Fan


Step 1: Determine Your Fan Size

If your manufacturer recommends the number of CFMs on square feet  - use the formula: Length x Width = Square Feet. If your manufacturer recommends the number of CFMs on cubic feet - use the formula:  Length x Width x Height = Cubic Feet. 

And some will use the formula discussed in Chapter 2; Length x Width x Height x .13 = Number of CFMs (round up to nearest 10).

Step 2: Determine Where You Will Vent the Air 

Your exhaust fan must vent outside.

Step 3: Understand Your Electrical Options

If you are not comfortable with this step, consult an electrician.

Step 4: Remove the Old Exhaust Fan

There are many steps and options to complete this section. Lowes lays out step-by-step instructions with images on your mounting options.

Option 1 involves mounting the exhaust fan with attic access.

Option 2 involves mounting without attic access. 

Decide which suits your current situation.  

Bathroom exhaust fans are a crucial element that should not be overlooked in your home. It is important that you install an exhaust fan of high quality, that way you can rest assured knowing you made a smart investment.

Chapter 5

Efficient Bathroom Exhaust Fans 

ENERGY STAR®, is the "government-backed symbol for energy efficiency, providing simple, credible, and unbiased information that consumers and businesses rely on to make well-informed decisions." 

Earning the Energy Star means the "product meets strict energy efficiency guidelines set by the US Environmental Protection Agency."

One of the certified products they suggest is the Greenheck SP-80-VG as one of the premium plus bath fans. 

According to Energy Star, "This fan utilizes an EC motor that is extremely energy efficient and allows the installer to balance the fan to precisely meet the ventilation demands of a given space." [source

This provides better efficiency and comfort with less noise.

It also includes lighting, three speeds, and 0.3 sones rating. Installing acceptable ventilation will help control moisture and remove foul odors.

Simple Toilet gathered the best exhausting fans for 2018. They conducted a survey and scoured over customer reviews to come up with their list - Best Bathroom Exhaust Fans Reviews & Guide.

The factors considered to make the list:

  • airflow capacity
  • special features
  • style and color
  • level of noise
  • budget

Chapter 6

Care and Maintenance of Fans

Is it time to clean that neglected bathroom exhaust fan?

If you see dust on the fan, you are long overdue. If you notice more steam than usual on the mirror, you are long overdue.

Need a quick test to see how efficient your exhaust fan is working?

Hold a piece of toilet paper up to the fan. If it's getting sucked up by the fan, it's still working. 

Having a clean and functional fan in your bathroom is just as important as any other cleaning job in your home. (washing machine, refrigerator, etc.) Stop putting the task off.

Airflow and exchange are necessary. Deep clean your fan at least once a year. 

10 steps to follow for a dirt-free, mold-free fan:

Step 1: Turn the fan off at the circuit breaker or switch. No electricity allowed.

Step 2: Remove the cover. Pull the fan cover down gently. If there are metal pins/spring clips on each side, squeeze gently to release the fan cover. You may see just a tab depending on the model.

Step 3: Wash the fan cover in a sink with soap and warm water. Or vacuum to clean the vent cover.

Step 4: Unplug the fixture.

Step 5: Depending on the model of your fan, remove visible screws and motor. (we are going in for a deep cleaning)

Step 6: Clean the fan blades and surrounding motor parts with a damp cloth. If you are not comfortable taking the motor out, you can just vacuum inside the fan housing and around the motor. 

Step 7: Clean the exhaust vent and surrounding area. Let everything dry out before replacing your vent cover.

Step 8: Reinstall your exhaust fan. 

Step 9: Turn the electricity back on.

Step 10: Enjoy a cleaner, more efficient exhaust.

Need a visual?

Our friends at One Good Thing, give you a step by step with images and all.


If you take care of your bathroom exhaust fan, it will take care of your bathroom’s air.

Your home consists of heating and air conditioning systems that are essential to the comfort and well-being of your home and goes well beyond your bathroom.

Ventilation is part of HVAC (heating, ventilation, and air conditioning) that provides comfort and good air quality. It's important to choose an HVAC company that understands correct ventilation as well as heating and cooling.

If you need HVAC service, one of our technicians would be happy to help you.

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