Local Mechanical Exhaust
In each kitchen, a system shall be installed that exhausts directly to the outdoors and meets one of the following Rater-measured airflow standards: *
Continuous rate is ≥ 5 ACH, based on kitchen volume.
- ENERGY STAR recommends selecting a fan that provides more than 5 air changes per hour (ACH) in order to pull the required amount.
Intermittent rate is ≥ 100 CFM and, if not integrated with range, also ≥ 5 ACH based on kitchen volume.
- ENERGY STAR recommends selecting a fan with a rating of 150 to 200 CFM to pull at least 100 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 the exterior of all ventilation ducts, preferably with mastic.
- ENERGY STAR recommends testing the kitchen fan after completing a visual inspection of proper duct sealing.
* All kitchen fans must comply with either the continuous of 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.
Kitchen volume shall be determined by drawing the smallest possible rectangle on the floor plan that encompasses all cabinets, pantries, islands, and peninsulas and multiplying by the average ceiling height for this area. Cabinet volume shall be included in the kitchen volume calculation.
All intermittent kitchen exhaust fans must be capable of exhausting at least 100 CFM. In addition, if the fan is not part of a vented range hood or appliance-range hood combination (i.e., if the fan is not integrated iwth the range), then it must also be capable of exhausting ≥ 5 ACH, based on the kitchen volume. Also, for intermittent kitchen exhaust fans that are itnegrated with microwaves, a rated air flow rate ≥ 200 CFM may be used in lieu of measuring the actual air flow rate.
Kitchen Fan Rating
Kitchen 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 the HVAC Contractor to install 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).
Kitchen Fan Selection
To calculate the CFM requirement of the kitchen fan for continuous rate, use the equation below:
Required CFM = (5 ACH) * (Kitchen Volume) / (60 minutes)
If intermittent fan flow rate of at least 100 CFM is less than 5 ACH, based on kitchen volume, then a vented range hood is required.
Kitchen Fan Testing Tips
- Test the kitchen fan after completing a visual inspection of proper fan installation.
- Verify the kitchen fan is set to “exhaust” instead of “recirculate.”
- Use a flow hood, flow grid, anemometer (in accordance with AABC, NEBB, or ASHRAE procedures), or other equivalent method to test the fan.