5 Bath Fan Installation Mistakes to Avoid

Which of these installation gaffes do you recognize?


Foggy mirrors. Mold and mildew. Noisy operation. Contractors know all too well that many things can go wrong with a bathroom’s ventilation system, causing costly callbacks and distrust with homeowners.

However, few realize that these common bath fan failures are often the result of faulty installation – not a poor bath fan. Pros can reduce callbacks and strengthen their reputation by keeping an eye out for these common installation mistakes.

Common Bath Installation Mistakes

1) Opting for the Minimum

Often, contractors select a bath fan solely based on the CFM required to ventilate the space without considering other performance factors. Although basic ceiling mount bath fans will meet the minimum code requirements, they often fall short of homeowner’s expectations.

Builders and contractors can install remote mount bath fans to keep up with increasing demand for quiet, hassle-free ventilation. The bath fan motor is mounted in a remote location away from the ventilation grille to eliminate noise. These fans can also be used to ventilate two bathrooms with one fan, eliminating the need for two bath fans.

Selecting the right fan for your specific application is the first step to going beyond contractor-grade solutions. You can use Fantech’s bath fan selector tool to explore options based on factors like the number of bathrooms, exhaust point, grille preferences and more.

2) Selecting the Wrong Size

Most contractors think that selecting a bath fan that is too small for the CFM requirements is the only sizing issue they can make. However, oversizing can be just as detrimental because it can create imbalance by pulling out too much air. This deficit causes unfiltered outside air to be pulled into the space through leaks and cracks.

According to the guidelines of the Home Ventilating Institute (HVI), baths that are 100 square feet or smaller require 1 CFM per square foot of bathroom or a minimum 50 cfm of fresh airflow. To find the square footage simply multiply the length of the bath by the width.

Bath Fan Sizing for Single Bathroom

This math changes slightly when working in luxury bathrooms that include features like jetted tubs. A standard tub, shower or toilet requires 50 CFM. By contrast, a whirlpool, garden or jetted tub requires 100 CFM.

Another unique example is using a remote bath fan to ventilate two bathrooms with one fan. In these instances, simply add the CFM requirement of the two bathrooms together. 

Bath Fan Sizing for Full and Half Bathroom

3) Placing the Fan in the Wrong Location

Do you typically place the bath fan in the center of the room? Although this is a very common practice, it is actually the culprit behind those pesky foggy mirrors and moisture buildup. 

When the fan is in the center of the bathroom, it actually drags the moisture from the shower across the room rather than venting it straight out and away. To prevent this, bath fans should be placed in the shower or just outside of the shower to eliminate moisture at the source.

Keep in mind that the primary purpose of a bathroom ventilation system is to remove moisture from the air. While bath fans also offer a solution to eliminate odors and ensure fresh air, the design and placement should always support the fan’s primary purpose.

4) Driving Up Energy Costs with Multiple Fans

Large, luxury bathrooms. Water closets. Home spas with jet tubs. These bathroom applications often require several ventilation points, causing contractors to install multiple fans to meet CFM requirements.  

While multiple fans can do the job, they often drive up energy costs and create excessive noise when operating simultaneously. Rather than install and operate two bath fans, a PB Series remote bath fan can be used to vent two exhaust points using one fan. Not only is this a more cost-effective solution, it’s less noisy. 

PB Remote Bath Fans ventilate two bathrooms with one fan

5) Thinking Only About Function and Overlooking Design

If a homeowner is paying for a high-end bathroom, the last thing they want is a clunky eyesore on the ceiling. But, as mentioned earlier, most contractors take a functional approach to their bath fan selection without weighing design factors.

Selecting a remote bath fan with smaller, sleeker grilles makes ventilation less obtrusive than traditional ceiling mount fans. Homeowners will appreciate having silent ventilation that goes unnoticed.

Fantech Bath Fan Grille Sizes vs. Traditional Grilles

Traditional bath fans are approximately 15-20” in diameter. The PBLremote bath fan offers 7” grilles for a sleek design option and the ability to include lighting.

Have more questions about proper bath fan installation? Get answers to all of your bathroom ventilation questions in our frequently asked questions.

Find Premium Bathroom Ventilation Solutions

It takes more than proper installation to provide effective bathroom ventilation. Selecting the right bath fan for your specific application is the first step to providing effective bathroom ventilation.

Find your perfect  Use the NEW bath fan selector tool and find a dealer near you. 

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Fantech makes air quality control easy thanks to decades of research, development, and refinement that continue to push the industry forward. Learn which Fantech solution is the best fit in your next project today.