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Fantech Bath Fan Sizing Examples

Unlike standard exhaust fans, the motor of a Fantech fan mounts in a location away from the living area such as an attic. Small unobtrusive Ceiling Grilles, with or without lights, can be mounted in multiple locations over the shower, the toilet and/or the tub then ducted to the remote fan to quickly and efficiently whisk away moisture, steam and odors. One fan can also be used to ventilate two bath-to-back baths.  You can use our Quick Sizing Calculator under the learning center called Fantech Bath Fan Sizing.


Bath Fans Sizing for under 100 Square Foot Bathroom

Bath Fans Sizing for under 100 Square Foot Bathroom

Clear the air in smaller baths and powder rooms with the help of a Fantech Premium Bath Fan or Bath Fan with Light. A small-scale grille mounts in the ceiling while the fan motor mounts in a remote location away from the living area. The result is quiet yet powerful ventilation that is sure to protect your home from the damaging effects of moisture, steam and mold.

According to the guidelines of HVI (Home Ventilating Institute) baths 100 square feet or smaller require one CFM per square foot of bathroom*. To find the square footage simply multiply the length of the bath by the width.

EXAMPLE 7 Feet By x 9 Feet bath = 63 square feet YOU WILL NEED A 63 CFM FAN. (Minimum 50 CFM)

NOTE: For proper airflow in typical installations (when duct losses aren't calculated), use the 0.4"Ps (static pressure) rating point for correct fan selection.



Bath Fans Sizing for over 100 Square Foot Bathroom

Bath Fans Sizing for over 100 Square Foot Bathroom

As the trend to larger spa-like bathrooms continues to gain in popularity, the need for proper ventilation becomes more important.

Gone are the days of a single bath fan in the center of the room. The key to proper ventilation in oversized baths filled with luxurious amenities is true spot ventilation at the source.

Quick removal of moisture at the source will keep your beautiful bath free of mold and the effects of extreme moisture.

Fantech has developed its Premium Bath Fans so that one remote mounted fan motor can effectively ventilate several areas of the bath.

Ceiling Grilles or Ceiling Grilles with Lights can be easily positioned over showers, whirlpool tubs, steam showers, toilet and vanity. Ventilation for baths over 100 square feet is calculated based on the fixtures in the bath. Allow 50 CFM for each standard toilet, shower or tub. Whirlpool and jetted tubs are calculated at 100 CFM. Add up the CFMs for all fixtures and you'll have the total CFMs required.


11 Feet x 14 Feet Bath = 154 square feet

1 Toilet + 1 Shower + 1 Jetted Tub = 150 CFM

1 Toilet 50 CFM

1 Shower 50 CFM

1 Jetted Tub 100 CFM

YOU WILL NEED A 200 CFM FAN. (Minimum 50 CFM)

NOTE: Fantech recommends that steam showers use a separate fan on a timer so that the fan may be shut off during shower use and then run afterward to dry the shower stall.



Master Bath with 1 Fan and 2 Grilles Application

Master Bath with 1 Fan and 2 Grilles Application

270 CFM fan with two Ceiling Grilles and two grille housings with dampers and Y-adapter (4x4x6). Uses 4 Inch and 6 Inch duct.