Bathroom Exhaust Fan Buying Guide

Under the wrong conditions, the warm, moist air produced by showers and baths can be detrimental to your health and your home. High humidity creates the perfect breeding ground for mold and mildew. These indoor pollutants can trigger allergies, asthma, and other respiratory problems, and eat away at sheetrock and wall studs.  

Installing a new exhaust fan—or replacing an old, inefficient one—will allow you to control the humidity level, head off damage, and remove odors from your bathroom. There are different types of bathroom fans to choose from so it’s a good idea to find the bathroom fan size and features to best fit your home. We’ve put together this guide to explain the different types of fans available and help you decide which is best for your home. 

Before Choosing an Exhaust Fan

With so many different types of bathroom fans to choose from, it’s important to find the exhaust fan that can meet the task requirements. When choosing a built-in fan, look for the most important features, from the CFM, the sones, or the visual impact the fan has on the rest of the room design, whether it is a kitchen, bath, or basement location. 

What is CFM?

One of the most influential factors of any exhaust fan purchase is the CFM, which is another way of saying the cubic feet per minute. The CFM rating indicates the amount of air that the exhaust fan can move through in one minute, under laboratory conditions. The higher the CFM number, the more cubic feet of air the fan can process and the better the ventilation potential. 

The air in the room becomes saturated from the moisture created by each water fixture in the room. The number of fixtures adds to the humidity regardless of the kitchen or bathroom fan size and will influence the required CFM for the room’s square footage. This means that the more faucets, toilets, or water-consuming appliances in the room, the higher the bath fan CFM will need to be. 

An effective bathroom fan should completely refresh the air in a bathroom 8 times in an hour, or just about once every 7.5 minutes. Look for a fan with a CFM that can accommodate the bathroom size at that rate. 

Use this calculator to figure out the correct number of CFM needed for your bath fan. 

Bathroom Length (ft) x Bathroom Width (ft) x Bathroom Height (ft) x 0.13 = Minimum CFM needed 

For example if the bathroom length is 12 ft and the width is 7 ft, with a ceiling height of 8 ft, the room would need a fan with a minimum CFM of 87.36, and the equation would look like this: 

12 x 7 x 8 x 0.13 = 87.36 

For bathrooms under 100 square feet, with an 8-foot high ceiling, the average minimum bathroom exhaust fan size is 1 CFM per square foot. The larger the bathroom, or the more water fixtures in use in the space, the more CFM will be needed to clear the moisture content from the room. 

Exhaust Fan Specifications

There are many options when choosing a bath fan, from location to fan size and design, as well as a variety of more technical specifics that are just as important to consider. To find the best bathroom exhaust fan, you’ll need to know what these details mean and how they matter. 

• Amperage (Amps): The amps rating on a fan is a measurement of the energy the fan uses to operate at highest capacity. The higher the number of amps, the more energy it requires. 
• Duct size: To match the duct size, measure the diameter of the duct that connects to the fan. The duct should be sufficient size to move air to and from the exhaust fan. 
• Sones: The perceived loudness of the exhaust fan is indicated in sones. It is not measured in specific decibels or volume levels, but rather is an indication of the comparative comfort level of someone who hears the sound. For instance, a quiet kitchen refrigerator may be about 1 sone, while an energy efficient exhaust fan can get up to 3.0 sones.  
• Static Pressure (SP): The velocity of the air in the ducts adds resistance as it turns corners and moves air along the length of the duct, which creates static pressure that the exhaust fan must have the power supply to overcome as it expels air from the room. 
• UL Listing: The UL Listing is a reference to the rating from the Underwriter’s Laboratory assigned to indicate whether the fan is equipped for a damp or wet environment. 
• Volts: An indication of the amount of electrical force that the fan must be provided in order to draw the correct amperage from. 

Knowing these basic terms helps ensure that the exhaust fan you choose will meet the requirements of the room where it is installed. 

Types of Bathroom Fans

The look and installation characteristics of the different types of bathroom fans leave them easy to categorize and can help narrow down the search for the right exhaust fan.  

Standard Exhaust Fans

Standard exhaust fans are solid replacements for older exhaust fan installations. They provide an updated look but are often the same bulky installation footprint, with an emphasis on functionality over form. 

• Mounted in the ceiling or a wall, with the fan case often sticking out into the room. 
• May include an integrated light or other basic features. 
• Standard exhaust fans are often found as bath fans with heaters or heat lamps. 

In-line Fans

In-line fans are installed within the attic or crawl space, unseen and relatively quiet. They connect within the duct work and can be used to provide ventilation for multiple rooms or to vent to multiple exhaust points for increased airflow. 

• Installed in the attic.  
• The motor does not rest on the bathroom ceiling or against the wall, which allows the bathroom exhaust fan to be hidden behind a standard or decorative wall vent. 
• The motors are often more powerful, resulting in more effective exhaust fans than standard models. 
• A quieter bathroom fan. Their installation within walls or attic spaces provides better sound proofing. 
• If the CFM number for the bathroom seems significantly high, then consider the in-line fan option to reduce the sound heard within the bathroom space. 

Decorative Exhaust Fans

Decorative exhaust fans are designed to be more aesthetically pleasing and blend in with the rest of the room, often with a lower sone rating. They often resemble decorative light fixtures and are available in styles to match the room decor. Look for decorative fans that have additional features.  

• Designed to look like decorative light fixtures 
• Available in styles to match your decor 

Must-Have Bath Fan Features

Exhaust fans don’t have to be boring and noisy editions to the bathroom. There are customizable options when choosing the best bathroom exhaust fan. Not only can you choose a quiet bathroom fan, you can select from various other helpful and convenient technological improvements to keep everyone in the household glad to use the benefits of the exhaust fan.   

Heater

An exhaust fan with a built-in heater or heat light keeps your bathroom warmer. They are especially useful in winter, or to keep the air temperature in the room closer to that of the shower temperature when in use. 

Humidity Sensing Bath Fans

Humidity sensing exhaust fans initiate the fan when internal sensors detect increased humidity in the room. This could be from water use or even from weather changes.

Title 24 Compliant

To meet the state’s set building standards, California customers need to ensure that their bath fans are California Title 24 compliant. This ensures that the fan is energy efficient and meets expectations for air quality.

HVI Certified

The Home Ventilating Institute is a nonprofit lab that assures products meet particular standards for ventilation use. Certified fans will be an extra assurance that you're getting the best air quality from the product you purchase.

The Newest and Best Exhaust Fan Features 

For those high-tech bonuses that you know you really want, hold-out and look for exhaust fans that have these extra features:

• Bluetooth® Speakers: These fans include wireless speakers that allow you to connect and play music using Bluetooth® technology. 
• Lights: Bath fans with lights keep your bathroom safe and easy to see at night. 
• Motion Sensor: Initiates the exhaust fan and other features when someone enters the room. 
• Timers: Keeps the fan running for a pre-set amount of time, often providing a range of choices from 15 minutes to 60 minutes or more. 

Energy Star Criteria

Energy Star certified products meet requirements established by the EPA regarding energy efficiency. Household exhaust fans with the Energy Star label provide greater energy savings and comfort with less noise.  

Household exhaust fans with the Energy Star label provide: 

• Greater efficiency and comfort with less noise. 
• Improved performance motors. 
• Improved blade design for better performance and a longer life span.  

To qualify for an Energy Star rating, a bathroom exhaust fan must meet a certain standard for sound output as well as energy consumption. The sound levels are measured in sones, and the maximum allowable levels are established according to the airflow velocity of the fan, shown as the fan CFM. 

A good breakdown of the sones allowed from an Energy Star exhaust fan is shown in this sones per CFM chart. 

These models often offer top of the line motors and improved blade design for better performance and a longer life span. They are designed to use less electricity and save money over time on the household electric bill. An Energy Star certified exhaust fan can save as much as 70% of the energy used by older, less efficient models. Look for Energy Star certified products to ensure your home is as comfortable, safe, and energy efficient as possible, particularly when it comes to the important work of the bathroom exhaust fan.