Local Mechanical Exhaust
Continuous rate is ≥ 20 CFM
- ENERGY STAR recommends selecting a fan with a rating of 50 CFM to pull at least 20 CFM when measured.
Intermittent rate is ≥ 50 CFM
- ENERGY STAR recommends selecting a fan with a rating of 70 CFM to pull at least 50 CFM when measured.
Continuous and Intermittent
- Install the fan to directly exhaust to the outdoors through a termination with little or no restriction.
- Seal all seams, gaps, holes, and connections to exterior of all ventilation ducts, preferably with mastic.
- ENERGY STAR recommends completing a visual inspection of proper fan installation, prior to testing the fan.
* All bathroom fans must comply with the continuous or intermittent rate.
The whole-house ventilation air flow and local exhaust air flows shall be measured by the Rater using a flow hood, flow grid, anemometer (in accordance with AABC, NEBB, or ASHRAE procedures), or substantially equivalent method.
Per ASHRAE 62.2-2010, an exhaust system is one or more fans that remove air from the building, causing outdoor air to enter by ventilation inlets or normal leakage paths through the building envelope. Examples include bath exhaust fans, range hoods, and clothes dryers.
Per ASHRAE 62.2-2010, a bathroom is any room containing a bathtub, shower, spa, or similar source of moisture.
An intermittent mechanical exhaust system, where provided, shall be designed to operate as needed by the occupant. Control devices shall not impede occupant control in intermittent systems.
Bathroom Fan Rating
A bathroom is any room containing a bathtub, shower, spa, or similar source of moisture.
Bathroom fans are typically rated by how many cubic feet per minute (CFM) the fan will exhaust in a factory setting. Duct work, termination choices and installation may decrease the measured CFM below the factory-rated CFM.
To ensure the installed fan exhausts the correct amount of CFM, ENERGY STAR recommends installing a fan with a rating higher than the required measured amount.
For additional information and specific duct testing protocols please refer to RESNET Chapter 8 (Standard for Performance Testing and Work Scope: Enclosure and Air Distribution Leakage Testing).
Bathroom Fan Testing Tips
- Test the bathroom fan after completing a visual inspection of proper fan installation.
- Seal bath fans to the drywall, including conditioned areas. This will ensure air is exhausted from the bathroom and not the plenum.
- Use a flow hood, flow grid, anemometer (in accordance with AABC, NEBB, or ASHRAE procedures) or other equivalent method to test the fan.
- Verify that the control devices of the bathroom fan do not impede occupant control.
If the fan is not pulling enough:
- Verify the exterior termination is operating properly.
- Verify the fan damper swings freely and packing tape is removed.