If you have a very small bathroom of less than 50 square feet (4.6 square meters), you will want to use a minimum of 50CFM or slightly more. However, we recommend never going more than 10-20% large than the minimum CFM.
If you live in a neighborhood where all the houses have been built by the same contractor, chances are you have a 50 CFM fan. We recommend at least an 80 CFM for most bathrooms but a 100/110 for a larger master bathroom. This will help move the moisture out of the bathroom and reduce the risk of mold.
In an ideal situation (which never exists) a 50 CFM fan is good for a room about 50 square feet. In a real-world setting, it is probably closer to being able to handle a room between 35 and 40 square feet.
Most fans are rated from 50 to 110 CFM, but some models designed for large master bathrooms, rec rooms and home theaters can be rated even higher. Choose a fan that can ventilate at least 1 CFM per square foot of room. So, for an 80 square foot bathroom, select an 80 CFM fan.
For general HVAC purposes, the typical recommendation is approximately 1 CFM per square foot of floor area. However, this can vary depending on your specific needs, like room occupancy or the presence of certain appliances. Contact the Industrial Fans Direct team if you need help determining your requirements.
On the other hand, if your CFM is too high for your room size, it can cause ventilation problems. Too much air results in too little ventilation, which in turn causes high humidity. The excess moisture in the air can then lead to mold and mildew, as well as other problems.
A fan that is too big can cause a bathroom to be cold and noisy. This is why calculating the correct CFM is important.
The higher the CFM the more air it can move, so an 80 CFM fan and a 150 CFM fan will both work, but one will get the job done in about half of the time. Approximately. A good way to select the CFM you need is to use the square footage of the area it serves.
Factors to Consider When Choosing a Bathroom Exhaust Fan
The room's size determines the necessary cubic feet per minute (CFM) rating of the fan. The CFM rating measures the volume of air the fan moves. As a general rule, you'll need at least 1 CFM per square foot of space.
So, to increase the CFM (working from logic), you could increase the motor speed (but if it is a already a 3450 rpm motor there isn't much you can do). Or you could (maybe) modify the fan assembly to have a slightly bigger or more efficient fan. I guess that my recommendation is to go with a bigger exhaust fan.
CFM stands for Cubic Feet per Minute, and it tells you how many cubic feet of air your fan will move in a minute. You want to make sure that you're buying a bath fan that is going to properly ventilate your space, not over- or under-ventilate it. For bathrooms 45 square feet and less, purchase a 50 CFM fan.
Yes, your bathroom fan can be too big. A bathroom exhaust fan that is much too large for the area will only increase your energy bill, fill your space with cold air in the winters, and ultimately, not perform its job effectively.
The first things to consider when determining your ideal range hood CFM are your cooktop's width and BTU capacity. The general guidelines for each of these features are as follows: 100 CFM for every 12 inches of stove width. 100 CFM for every 10,000 BTUs of heat capacity.
For every square foot of space, you'll need at least 1 CFM. In practical terms, for a typical Indian bathroom of 6×8 feet (48 square feet), you'll need an exhaust fan that provides at least 48 CFM.
If you're looking for a fan that moves the most air, consider a large ceiling fan with a high blade pitch, a high-quality motor, and high RPM.
To fulfill the local exhaust airflow requirements of ASHRAE 62.2 (2010) and the International Residential Code (IRC 2021, Section M1507), bathroom fans should have a mechanical exhaust capacity of ≥ 50 cfm for intermittent operation or ≥ 20 cfm of ventilation when operated continuously.
A 50 CFM rating is recommended as a minimum for bathrooms 50 sq. ft. and smaller. Larger bathrooms require additional ventilation capacity.
We recommend the Broan-NuTone Roomside Series Exhaust Fan as the best overall bathroom exhaust fan, which is suitable for bathrooms up to 75 square feet. If you want the quietest bathroom exhaust fan, however, then go with the Panasonic WhisperChoice DC Pick-A-Flow Ceiling Exhaust Fan.
Points to consider:
Room size: For larger rooms, a 3 blade fan is ideal due to its higher air circulation. A 4 blade fan provides consistent airflow and quieter operation for smaller or medium-sized rooms. Noise level: If noise is a concern, opt for a 4 blade fan as it operates more quietly than a 3 blade fan.
The larger the space, the higher the fan CFM must be in order to efficiently cool a room. CFM for fans is a critical measurement for determining the right fan for your space. If the CFM is too low, the room will be unable to be cooled and undermine any energy efficiency of the fan.
It is considered that 135 CFM is needed per square foot of space. So 13.5 CFM would be required for a 100-square-foot area. A room of 1,000 square feet would require 135 CFM.
CFM (cubic feet per minute) is a metric that determines how much air is pushed by the system to heat, cool, or ventilate a certain area. This measurement is helpful when determining which size and power output is needed for a space. A rule of thumb is that spaces need 1 CFM per square foot.
Upgrading to a bigger bath fan can significantly improve your bathroom's ventilation, reducing moisture and preventing mold growth.
Your Bathroom Fan Is a Fire Hazard
From there, it's so easy to forget about the bathroom fan completely! There are consequences for leaving the fan on too long, though. Leaving the exhaust fan running for an extensive period of time can cause significant wear to the motor and may cause a fire.
You can vent a bathroom exhaust fan through the wall or roof. Either is fine, but the shorter the route, the better.