Kitchen Exhaust

Scope

Kitchens should be equipped with an exhaust fan that vents directly outdoors
Kitchens should be equipped with an exhaust fan that vents directly outdoors

Install an exhaust fan in the kitchen to exhaust steam and cooking odors to the outdoors.

  • Install the fan to vent outdoors, not into an attic, crawlspace, or space between floors.
  • Choose a smooth metal duct with the diameter specified by the fan manufacturer.
  • Install the duct with the most direct route to the outside with as few bends as possible.
  • Seal all seams and around ceiling and wall or roof penetrations with mastic or spray foam. Flash exterior surfaces as needed.
  • Install a fan that meets Rater-measured airflow codes and standards for local exhaust; meet whole-house ventilation requirements if the kitchen fan is used for whole-house mechanical ventilation. 

See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and Indoor airPLUS.

Description

Regardless of what kind of ventilation system you have for the rest of the house, an exhaust fan should be installed in the kitchen to provide point or local exhaust to remove moisture and odors associated with cooking. The exhaust fan is typically located directly over the kitchen stove and is installed in a range hood or cabinet, integrated with a microwave oven, or mounted on the wall. The fan should be ducted to exhaust outside of the home, not into the attic, crawlspace, or another area inside the building. The duct serving the range hood should be made of rigid metal such as galvanized steel, stainless steel, or copper and have a smooth interior surface. It should meet the maximum length guidelines specified in the IRC (2015 IRC Table M1506.2) and the minimum diameter guidelines specified in the fan’s installation instructions; small-diameter ducts could trap grease, creating a fire hazard. It should be airtight, equipped with a back-draft damper, and independent of all other exhaust systems. 

Recirculating fans that draw air through a filter and discharge it back into the room are not acceptable. Operable windows are a nice feature but they should not be relied on for consistent ventilation.

Kitchen fans can be run intermittently (occupant controlled) or continuously; some fan models have multiple speed settings and can be used for either.To fulfill the local exhaust airflow requirements of the International Residential Code (IRC 2015), kitchen fans operated intermittently should have a flow rate of 100 cfm or more and fans operated continuously should have a flow rate of 25 cfm or more. Select fans that are ENERGY STAR rated, and have low sound ratings and low power draw. ENERGY STAR recommends that local kitchen exhaust fans provide ≥ 5 air changes per hour of ventilation, depending on the kitchen volume. ENERGY STAR also recommends that exhaust fans have sound ratings of ≤ 1 sone if set to run continuously or ≤ 3 sones if operating intermittently.

Some home owners are installing commercial-scale cooking ranges with very powerful exhaust hood fans rated as high as 1200 cfm. Exhaust fan rates this high can easily backdraft a non-sealed-combustion furnace, water heater, or fireplace (Holladay 2010). Any installed exhaust fan operating in excess of 400 cfm must be provided with a makeup air system that will automatically start and operate simultaneously with the exhaust fan and will provide makeup air at a rate equivalent to the exhaust fan rate.

Although a single-point exhaust fan such as a kitchen fan could be used to provide code-required whole-house ventilation, this strategy is not recommended. For more on whole house ventilation strategies and requirements, see the Building America Solution Center Guide Whole-Building Delivered Ventilation.

Kitchen exhaust fans may be installed by the HVAC vendor or installer or by the kitchen range vendor if it is part of that system. This task should be included in the contract for the appropriate trade depending on the workflow at specific job sites.

How to Install Exhaust Fans

  1. Determine the appropriate fan size for your application. For a continuous rate of ≥ 5 ACH, ENERGY STAR recommends selecting a fan that provides more than 5 ACH in order to pull the required amount of air. For an intermittent rate of ≥ 100 cfm, ENERGY STAR recommends selecting a fan with a rating of 150  to 200 cfm. Choose ENERGY STAR-rated fans for energy efficiency and low noise level.

Proper sizing of kitchen exhaust fan 

2.  Install the fan either in the range hood, the cabinet above the stove, or on the wall above the stove. Follow the manufacturer’s instructions. The fan may also be purchased as an integrated unit that comes with a microwave oven mounted into a cabinet above the stove. Cut openings in the ceiling for the fan or exhaust duct no wider than needed to fit the fan or duct and air seal the opening with caulk or spray foam. Connect the exhaust duct to the fan box with mechanical fasteners and seal with metal tape and/or mastic. Do not use cloth-backed duct tape.

3. Vent the kitchen fan exhaust directly to the outside, not into an attic, crawlspace, or space between floors. Use correctly sized, smooth metal duct. Seal seams and joints with mastic and/or metal tape. Install a back-draft damper that closes when the fan is not in operation. Install the duct with as few bends as possible and out of the way of other ducts or equipment in the attic. Take care not to dent or crush the duct during or after installation. The duct should be independent of other exhaust systems.

4.  Locate the exhaust duct outlet vent on the exterior of the home at least 10 feet from any air inlet. The outside termination should be covered with louvers, a screen, or a grille. The exhaust air should not be directed onto a walkway.

5.  If the fan is integrated with a microwave oven installed over the stove, install it according to the manufacturers’ instructions and 2015 IRC Section M1504.

6.  Exhaust hoods installed over domestic open-top broiler units should be made of metal and have a 1/4-inch clearance between the hood and the underside of combustible material or cabinets. The hood should extend the full width and depth of the cooktop, discharge to the outside, and have a backdraft damper, as specified in 2015 IRC Section M1505.

7.  The exhaust fan flow rate should be tested by a certified energy rater using test procedures listed in ANSI/RESNET/ICC 380-2016.

Ensuring Success

Visually inspect and test the kitchen exhaust fan for proper installation as follows:

  • Ensure that the fan exhausts outside, not into the attic; that it is set to exhaust, not recirculate; that any dampers on the outside termination are able to open freely; and that packing tape is removed.
  • Confirm that any openings cut in the ceiling for the fan or exhaust duct are properly air sealed and that the exhaust duct is sealed to the fan box with both mechanical fasteners and mastic and/or metal tape and caulk or spray foam.
  • Check the sone rating; ASHRAE 62.2-2007 requires 3 sones or less for intermittent (occupant-controlled) kitchen or bath exhaust fans or 1.0 sone or less for continuous fans.
  • See the Compliance tab for code and ENERGY STAR guidelines regarding flow rates and efficacy for fans used for local exhaust. See the guide Whole Building Ventilation for codes and standards related to exhaust fans used for whole-house ventilation.
  • A certified energy rater will test the fan’s operation to determine the flow rate using a flow hood, flow grid, anemometer, in accordance with test procedures listed in ANSI/RESNET/ICC 380-2016, or established by the Associated Air Barrier Council, National Environmental Balancing Bureau, or ASHRAE), or other equivalent method. Kitchen fans are typically rated by how many cubic feet per minute the fan will exhaust in a factory setting. Duct work, termination choices, and installation may decrease the measured cubic feet per minute below the factory-rated value.

Climate

No climate-specific information applies.

Training

Right and Wrong Images

Presentations

None Available

Videos

  1. Bathroom and Kitchen Exhaust Fans (1)
    Publication Date: July, 2015
    Courtesy Of: Panasonic

    Video describing how to properly install a retrofit bath fan.

  2. Bathroom and Kitchen Exhaust Fans (2)
    Publication Date: July, 2015
    Courtesy Of: Panasonic

    Video describing how to properly install a retrofit vent cap.

CAD Images

None Available

Compliance

The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

ENERGY STAR Certified Homes

ENERGY STAR Certified Homes (Version 3/3.1, Revision 08), Rater Field Checklist

7. Whole-House Mechanical Ventilation System

7.1 Rater-measured ventilation rate is within either ± 15 CFM or ±15% of design value (2.3)42
7.4 System fan rated ≤ 3 sones if intermittent and ≤ 1 sone if continuous, or exempted.43 

8. Local Mechanical Exhaust - In each kitchen and bathroom, a system is installed that exhausts directly to the outdoors and meets one of the following Rater-measured airflow and manufacturer-rated sound level standards:42, 47
8.1 Kitchen Airflow at Continuous Rate: ≥ 5 ACH, based on kitchen volume49, 50
8.1 Kitchen Sound at Recommended Continuous Rate:  ≤ 1 sone 
8.1 Kitchen Airflow at Intermittent Rate: ≥ 100 CFM and, if not integrated with range, also ≥ 5 ACH based on kitchen volume48,49, 50, 51
8.1 Kitchen Sound at Recommended Intermittent Rate: ≤ 3 sones

Footnotes:

(42) The whole-house ventilation air flow and local exhaust air flows shall be measured by the Rater using RESNET Standard 380 upon publication and, in the interim, a flow hood, flow grid, anemometer, or substantially equivalent method.

(43) Whole-house mechanical ventilation fans shall be rated for sound at no less than the airflow rate in Item 2.3 of the HVAC Design Report. Fans exempted from this requirement include HVAC air handler fans, remote-mounted fans, and intermittent fans rated ≥ 400 CFM. To be considered for this exemption, a remote-mounted fan must be mounted outside the habitable spaces, bathrooms, toilets, and hallways and there shall be ≥ 4 ft. ductwork between the fan and intake grill. Per ASHRAE 62.2-2010, habitable spaces are intended for continual humanoccupancy; such space generally includes areas used for living, sleeping, dining, and cooking but does not generally include bathrooms, toilets, hallways, storage areas, closets, or utility rooms.

(47) Continuous bathroom local mechanical exhaust fans shall be rated for sound at no less than the airflow rate in Item 8.2. Intermittent bathroom and both intermittent and continuous kitchen local mechanical exhaust fans are recommended, but not required, to be rated for sound at no less than the airflow rate in Items 8.1 and 8.2. 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 (e.g., bath exhaust fans, range hoods, clothes dryers). Per ASHRAE 62.2-2010, a bathroom is any room containing a bathtub, shower, spa, or similar source of moisture. 

(48) 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.

(49) 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.

(50) For homes permitted through 01/01/2014: Homes are permitted to be certified without enforcement of this Item to provide partners with additional time to integrate this feature into their homes. For homes permitted on or after 01/01/2014: Homes shall meet this Item. Alternatively, the prescriptive duct sizing requirements in Table 5.3 of ASHRAE 62.2-2010 are permitted to be used for kitchen exhaust fans based upon the rated airflow of the fan at 0.25 IWC. If the rated airflow is unknown, ≥ 6 in. smooth duct shall be used, with a rectangular to round duct transition as needed. Guidance to assist partners with these alternatives is available at energystar.gov/newhomesresources. As an alternative to Item 8.1, homes that are PHIUS+ certified are permitted to use a continuous kitchen exhaust rate of 25 CFM per 2009 IRC Table M1507.3.

(51) 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 with the range), then it must also be capable of exhausting ≥ 5 ACH, based on the kitchen volume. 

ENERGY STAR Revision 08 requirements are required for homes permitted starting 07/01/2016.

DOE Zero Energy Ready Home

Exhibit 1: Mandatory Requirements. Certified under ENERGY STAR Qualified Homes Version 3. EPA Indoor airPLUS Verification Checklist.

American Society of Heating, Air-Conditioning and Refrigeration Engineers (ASHRAE)

ASHRAE Standard 62.2-2010 Ventilation for Acceptable Indoor Air Quality in Low-Rise Residential Buildings (available for purchase at link above). The standard provides minimum requirements for mechanical and natural ventilation systems intended to provide acceptable indoor air quality in low-rise residential buildings.

ANSI/RESNET/ICC 380-2016

Standard for testing Airtightness of Building Enclosures, Airtightness of Heating and Cooling Air Distribution Systems, and Airflow of Mechanical Ventilation Systems. Section 5.1 defines procedures for measuring the airflow of a mechanical ventilation system including a powered flow hood, an airflow resistance device, or a passive flow hood.

2009 IECC

Section 403.5 Mechanical ventilation (Mandatory). Automatic or gravity dampers are installed on all outdoor air intakes and exhausts.

2012 IECC

Section R403.5 Mechanical ventilation shall meet the requirements of the International Residential Code or the International Mechanical Code. Automatic or gravity dampers are installed on all outdoor air intakes and exhausts. Table R403.5.1 Mechanical Ventilation System Fan Efficacy for range hood and in-line fans shall be at least 2.8 cfm/watt.

2015 IECC

Same as 2012.

2009 IRC

Section M1507.3 Ventilation rate. Kitchen fans should have an exhaust rate of 100 cfm intermittent or 25 cfm continuous.*

2012 IRC

M1503 Range hoods should discharge to the outdoors through a metal duct made of galvanized steel, stainless steel, or copper; with a smooth interior surface that is air tight and equipped with a back draft damper. The duct should be independent of other exhaust systems and should not terminate in an attic, crawl space, or other inside space. Exhaust fans capable of exhausting ≥ 400 cfm should be mechanically or naturally provided with makeup air at a rate equal to the exhaust air rate. The makeup air system should have a gravity or electrically operated damper that automatically opens when the system operates and that is accessible for inspection.

M1504 Microwaves installed over a listed and labeled cooking appliance shall conform to the terms of the microwave’s listing and label and manufacturer’s installation instruction. The microwave oven shall also conform to UL 923.

M1505 Open-top broiler units should have a min. 28-gauge metal exhaust hood with ¼-inch clearance between the hood and the underside of combustible material or cabinets. The hood should be at least as wide as the broiler, and extend over the entire unit, discharge to the outdoors, and be equipped with a back draft damper.

M1506  Exhaust opening should terminate at least 3 feet from property lines, 3 feet from operable and non-operable openings into the building, and 10 feet from mechanical air intakes, except where the opening is located 3 feet above the air intake.

M1507 The whole-house mechanical ventilation system shall consist of one or more supply or exhaust fans, or a combination of such and associated ducts and controls. Local exhaust or supply fans are permitted to serve as such a system. Outdoor air ducts connected to the return side of an air handler shall be considered as providing supply ventilation. The whole-house mechanical ventilation system shall be provided with controls that enable manual override.

The whole house mechanical ventilation system shall provide outdoor air at a rate equivalent to the minimum rates shown in Tables M1507.3.3(1) and M1507.3.3(2), which are based on the home's floor area.

Local exhaust rates (per Table M1507.4) Kitchen fans should have an exhaust rate of 100 cfm if operated intermittently or 25 cfm if operated continuously.*

2015 IRC

Same as 2012. Duct length and diameters are specified in Table M1506.2 and are based on the fan flow rate, which should be in accordance with ANSIE/AMCA 210-ANSIE/ASHRAE 51.

* Due to Copyright restrictions, exact code text is not provided. For specific code text, refer to the applicable code.

This Retrofit tab provides information that helps installers apply this “new home” guide to improvement projects for existing homes. This tab is organized with headings that mirror the new home tabs, such as “Scope,” “Description,” “Success,” etc. If there is no retrofit-specific information for a section, that heading is not included.

Scope

Install or replace the kitchen exhaust fan, if the kitchen currently lacks an exhaust fan or the existing fan is a recirculating model or has insufficient draw, as determined by occupant experience or through fan testing by a home energy rater.

If the current kitchen fan exhausts into the attic, crawlspace, or between floors, replace the duct with one that exhausts to the outside.

See the assessment guide, Pre-Retrofit Assessment of Attics, Ceilings, and Roofs.

For more exhaust fan ventilation, see the U.S. Department of Energy’s Standard Work Specifications.

See the Scope tab for additional job specifications.

Description

Installation of a new kitchen exhaust fan is warranted if the kitchen currently has no exhaust fan or if the existing fan is a recirculating model that does not vent to the outside. Other reasons to replace the fan include noise or moisture complaints by the homeowner or fan testing as part of a home energy audit that reveals that the fan has insufficient draw. A less common reason to replace the fan is if it has too much draw. Commercial-grade cook tops that are installed in some home kitchen remodels often come with overly powerful exhaust hood fans that have exhaust flow rates far above what is required by code. If testing by a home energy rater reveals that the exhaust fan is, or could potentially, backdraft the fireplace or other combustion appliances in the home, and it is difficult to find wall space to install a vent large enough to supply a sufficient amount of makeup air to the kitchen, a less expensive option may be to replace the exhaust fan within the range hood with a fan that exhausts at a rate closer to what is required by code. Follow the installation instructions provided in the Description tab.

More Info.

Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

Case Studies

  1. Author(s): PNNL
    Organization(s): PNNL
    Publication Date: September, 2010

    Case study about new home construction in the hot-humid climate, part of a project building 100 new homes after hurricane Katrina.

References and Resources*

  1. Author(s): ASHRAE
    Organization(s): ASHRAE
    Publication Date: January, 2013
    Standard defining the roles of and minimum requirements for mechanical and natural ventilation systems and the building envelope intended to provide acceptable indoor air quality in low-rise residential buildings.
  2. Author(s): DOE
    Organization(s): DOE
    Publication Date: April, 2017

    Standard requirements for DOE's Zero Energy Ready Home national program certification.

  3. Author(s): EPA
    Organization(s): EPA
    Publication Date: December, 2015

    Document outlining the program requirements for ENERGY STAR Certified Homes, Version 3 (Rev. 08).

  4. Author(s): Holladay
    Organization(s): Green Building Advisor
    Publication Date: November, 2010

    If your kitchen has a powerful exhaust fan, it may be pulling air down your chimney or water-heater flue.

Contributors to this Guide

The following authors and organizations contributed to the content in this Guide.

Last Updated: 07/21/2017