Kitchen Ventilation Design Guide
in the selection & installation of kitchen exhaust fans or kitchen vent systems
POST a QUESTION or READ FAQs about kitchen ventilation system design, installation, choices, and best practices, Q&A on venting microwave appliances.
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This article discusses kitchen vent fans:
Kitchen vent fan types, ventilation rate, installation specifications, and noise ratings.
We also discuss downdraft fans and kitchen fan noise issues. Our page top photograph illustrates a high capacity vertical rise range hood in a New York home. This is the most-effective kitchen exhaust ventilation design, but attention to fire safety is required with this and all exhaust fan systems.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
Kitchen Ventilation Design Guide: how to choose & install a kitchen vent fan
Kitchens and bathrooms are key sources of indoor moisture and other pollutants. Kitchens produce particulates and atomized grease from cooking, and with a gas range,
they also produce combustion by-products including nitrogen dioxide and carbon monoxide.
Our photos illustrate a traditional through-wall kitchen exhaust vent fan installed ca 1970 [DF]. The outdoor termination for this kitchen exhaust fan requires occasional caulking, and periodically the entire fan assembly is removed and cleaned to remove accumulated grease.
A magnetically-attached cover is sometimes installed over traditional through-wall kitchen exhaust fans to avoid drafts or heat loss in cold weather.
Kitchen cooktops produce large amounts of water vapor,
atomized grease, particulates, and cooking odors. In addition,
gas cooktops produce combustion by-products,
including carbon dioxide, nitrogen dioxide, nitrous oxide,
and carbon monoxide.
[Click any image or table to see an enlarged version with additional detail, commentary & source citation.]
Some high-capacity ventilators are
designed to work from 24 to 30 inches above the cooking
surface, but the stronger fans increase the risk of backdrafting
other combustion appliances.
with microwaves typically project out only 13 to 15 inches
and miss most of the contaminants generated by the front
[Click to enlarge any image]
Required Kitchen Fan Ventilation Rate
The minimum ventilation rate for
kitchens required by the 2003 International Residential
Code is 100 cfm intermittent or 25 cfm continuous (if
part of a whole-house ventilation system).
experts recommend that overhead range hoods have a minimum
capacity of 150 cfm and recommend higher capacity
fans for open grilling, high-BTU commercial-style
ranges, and other cooking styles that generate greater than
average steam or smoke (see Table 6-14).
[Click any image or table to see an enlarged version with additional detail, commentary & source citation.]
A rule of thumb
for high-output ranges is 1 cfm of ventilation per 100
BTU’s of output. With high-powered fans, multi speed controls
are best so the fan speed (and noise) can be lowered
when full power is not required.
Installation Specifications for Kitchen Island Hoods
Island hoods are typically installed at
least 27 inches above the cook surface so they do not interfere
with sight lines.
Because they are farther from the
cooktop and subject to passing air currents, they require
more powerful fans than standard wall-mounted hoods.
HVI recommendations for wall-mounted and island hoods
are shown in Table 6-14 above.
Updraft Kitchen Exhaust Fan Fire Hazards
As Mr. Bliss noted above,
The most effective way to remove the moisture
and contaminants from a cooktop is with an overhead
range hood vented to the outdoors.
The interesting kitchen vent fan exhaust system shown at left was installed (we estimate) in this New York home in the 1930's. A combination of wood and metal site-built ductwork runs horizontally across an attic floor to a high-capacity exhaust fan located in the attic (green). The attic-mounted fan connects to a vertical roof exhaust port using asbestos fabric to avoid vibration damage problems.
I [DJF] was more concerned about the possible fire hazards in this long-in-place ductwork combined with a high capacity attic fan than with any possible asbestos worry.
Grease accumulating in a cool horizontal kitchen exhaust fan duct is a fire hazard, as might be a fan in this location without any fire detection control or shut-off device. Just sayin' ...
Downdraft Fans for Kitchens
Because they lack a canopy to catch
contaminants and must overcome natural convection,
downdraft fans are less effective than overhead range
hoods. Typically sized at 400 to 600 cfm or more, they
do a reasonable job of venting barbecues and grills, but
are less effective with pots and pans taller than about
Downdraft fans are either flush-mounted at
counter level or pop up about 8 inches at the back of the
Flush-mounted fans are typically located in the
center of the cooktop or to one side.
do an adequate job of capturing combustion gases,
as well as water vapor and cooking odors from pans
3 inches or shorter. Vapors from taller pots tend to
Pop-up fans in the rear do an adequate job of capturing
combustion gases and moisture, except for tall
pots on the front burners.
Kitchen Vent Fan Noise Ratings & Advice
Look for the unit with the lowest noise rating that
meets the ventilation requirements. Some hoods are rated
as low as 2.5 sones, although most range from 4 to 7 sones
at full power (one sone roughly equals the sound of one
Ductwork Suggestions for Kitchen Fans
Like bathroom fans, the airflow from kitchen
exhaust fans is generally rated at a static pressure of 0.1 in.
(see “Ductwork,” page 262).
This is roughly equivalent to
30 feet of smooth 7-inch round or 3 1/4x10 in. metal duct
venting a 200 cfm fan.
For good performance, the total
equivalent duct length, not counting the wall or roof cap,
should not exceed about 30 feet. Equivalent duct lengths
for common fittings are shown in Table 6-15.
[Click any image or table to see an enlarged version with additional detail, commentary & source citation.]
Watch out: most sources we reviewed specifically warn against using flexible metal duct and of course dryer duct for kitchen exhuast vents, both of which are fire hazards.
Backdrafting & Safety Issues with Exhaust Fans
With large-capacity exhaust fans of
200 cfm or greater, there is a risk of causing backdrafting
of a fireplace or atmospherically vented boiler, furnace, or
The potential for backdrafting can be tested by a heating system technician and should be conducted
with all household exhaust fans running to simulate the
worst-case scenario. A simple preliminary test can be done by holding a stick of incense next to the draft diverter or
dilution port of each combustion appliance with the furnace
fan on and off.
If the smoke spills into the room for more than 30 seconds,
then dedicated makeup air is most likely required.
Modest amounts of makeup air can be delivered through a
passive duct with an automatic damper, but significant
depressurization may require an active supply fan.
makeup air supply should be delivered into the kitchen or
a nearby room not blocked by a door. (For more information see BACKDRAFTING HEATING EQUIPMENT.)
This article series discusses current best design practices for kitchens and bathrooms, including layout, clearances, work space, and accessible kitchen and bathroom layout, clearances, turning space, grab bars, controls, etc.
We include advice on choosing and installing kitchen countertops, cabinets, and kitchen or bathroom flooring, sinks, and other plumbing fixtures and fixture controls such as faucets. A list of kitchen and bath product manufactures and sources is included just below.
Reader Question: do we really need kitchen venilation at all?
(Mar 13, 2014) Jim said:
If downdraft fans are not that effective -- and a hood over an island takes up a bunch of space -- why not just skip the ventilation completely?
Is ventilation required in a kitchen?
There are two separate questions: the desirability of ventilation + code requirements for it and the energy efficiency & design requirements for ventilation.
For the former, national model codes and state, provincial or local codes indeed require kitchen ventilation, though "exhaust" and "ventilation" are mingled and sometimes a bit confounded. Here is an excerpt from M.D. Ewert's discussion of the Oregon building code on kitchen ventilation:
The requirements for ventilation in the ORSC can be found in Section R303.2, which states that
... all habitable rooms are to be provided with an aggregate glazing area of 8 percent of the floor area, with a minimal openable area of 4 percent of the floor area being ventilated.
The purpose of the glazing and the portion that is openable is to provide both natural light and natural ventilation.
Since a kitchen is considered a habitable room, it would require (at a minimum) a window, door, or other openings which opens directly to the outdoors, with an aggregate opening of at least 4% of the floor area. Sect ion R303.2 also allows the use of adjoining rooms to be used when determining this ventilation requirement
For the latter, ANSI/ASHRAE/IES Standard 90.1-2010 sets energy efficiency requirements for kitchen exhaust hoods and is discussed by a US DOE article on kitchen ventilation - www.energycodes.gov
Building & Mechanical Codes & Standards for Kitchen Exhaust Venting
VENTILATION CODES - web page home, listing ventilation codes downloadable as PDF, excerpts appear below. This page includes ventilation codes for the U.S., Canada, and other countries.
ANSI/ASHRAE/IES Standard 90.1-2010 sets energy efficiency requirements for kitchen exhaust hoods
This document explains different occupancy classifications such as
Section 303, Assembly Group A Section 304, Business Group B Section 305, Educational Group E Section 306, Factory Group F Section 307, High-Hazard Group H Section 308, Institutional Group I
(this includes hospitals) Section 309, Mercantile Group M Section 310,
Residential Group, or R, R-1, R-2, R-3, R-4 Section 311, Storage Group S Section 312, Utility and Miscellaneous Group U
Also see the ICC version at https://codes.iccsafe.org/public/public/chapter/content/7814/ - cannot print nor save from this website
New Jersey Mechanical Code Chapter 5 EXHAUST STSTEMS [PDF] (2006), International Mechanical Code as adopted by the U.S. state of New Jersey, retrieved 2018/03/23, original source https://www2.iccsafe.org/states/newjersey/ NJ_Mechanical/PDFs/2006_Chapter%205-Exhaust%20Systems.pdf
KITCHENAID RANGE HOOD INSTALLATION MANUAL [PDF] (2012) KitchenAid
Countertop Appliances, 553 Benson Road,
Benton Harbor, MI 49022 USA, Tel: 1-800-541-6390, retrieved 2018/03/23, original source https://www.kitchenaid.com/ digitalassets/KXW9736YSS/ Dimension%20Guide_EN.pdf
Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
want to install a microwave over the existing range vent
(Dec 1, 2014) Anonymous said:
I want to install a microwave over the range with vent. The old system was a counter top stove with downdraft venting to the basement and outside. Instructions do not say anything about going down with the microwave vent and inspector says it has to be by instructions. Can I vent microwave vent out the back of the microwave, 90 degree down the wall (about 6 feet) into the original vent pipe in the basement?
Anon I would give the manufacturer a call with that question as the answer may be product specific.
Also in at the end of the article text above see the companion article
MICROWAVE OVEN VENT INSTALL
Question: can I send in a sketch for comment?
(Jan 4, 2015) Mike Mitsch said:
I am trying to install a Kitchen Range Hood and found this site -- the Kitchen Ventilation Design Guide is FANTASTIC. I wonder if I could email somebody a sketch of what I am trying to install be sure I have things right? My email is firstname.lastname@example.org. Let me know.
Sure, Mike, use the email found at the CONTACT us link found at page top or bottom and I'll send it along to Steve Bliss who wrote the section to which you refer to see if he can comment.
Question: need for a removable vent cover
(Apr 11, 2015) Marianne said:
I'm renovating a kitchen and purchased a vent insert with plans on building a wooden cover over it. Must the cover be removable for access to the insert?
Take a look at the installation guide for your vent system and be sure to respect the cleareances from combustibles. You may find that wood isn't the best idea.
Question: insulate the fan ducts in a commercial kitchen?
(Apr 14, 2015) Gian Karlo Sicat said:
In commercial used kitchens, do we need to insulate the ducting works? if yes, what type of insulation should we use? thanks
I don't know, haven't seen such ducts insulated, am concerned about fire ratings, and will research further.
Question: are vent hoods required for gas stoves in Hawaii? Problem with high winds.
(Apr 28, 2015) Jay said:
Are Vent hoods required for gas stoves in Hawaii where there is high volume tradewinds driven crossbreeze and close windows (5 feet at 12 oclock, 5 feet at 3 oclock and 14 feet at 6 oclock
Jay: this may help you:
First in priority, check with your local building department
Then see this Hawaii code citation:
SECTION 419 – COOKING UNIT CLEARANCE
419.1 Minimum Vertical Clearance. There shall be a minimum vertical clearance of not less than 30 inches between the cooking top of domestic oil, gas, and electric ranges and the underside of unprotected combustible material above such ranges. When the underside of such combustible material is protected with insulating millboard at least ¼-inch (6.4 mm) thick covered with sheet metal of not less than 0.021-inch thick (No. 28 U.S. gage)
or a metal ventilating hood, the distance shall be not less than 24 inches (610 mm).
Title 11, Administrative Rules of the Department of Health, State of Hawaii. discusses ventilation requirements.
And from the 2009 IRC
M1503.1 General. Range hoods shall discharge to the outdoors
through a single-wall duct. The duct serving the hood
shall have a smooth interior surface, shall be air tight and shall
be equipped with a backdraft damper. Ducts serving range
hoods shall not terminate in an attic or crawl space or areas
inside the building.
Exception: Where installed in accordance with the manufacturer’s
installation instructions, and where mechanical or
natural ventilation is otherwise provided, listed and labeled
ductless range hoods shall not be required to discharge to
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Questions & answers or comments about kitchen ventilation system design, installation, choices, and best practices
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"The Elimination of Unsafe Guardrails, a Progress Report," Elliott O. Stephenson, Building Standards, March-April 1993
"Are Functional Handrails Within Our Grasp" Jake Pauls, Building Standards, January-February 1991
Access Ramp building codes:
Access Ramp Standards:
ADA (Americans with Disabilities Act), Public Law 101-336. 7/26/90 is very often cited by other sources for good design of stairs and ramps etc. even where disabled individuals are not the design target.
ANSI A117.4 Accessible and Usable buildings and Facilities (earlier version was incorporated into the ADA)
ASTM F 1637, Standard Practice for Safe Walking Surfaces, (Similar to the above standards)
American Plywood Association, APA, "Portland Manufacturing Company, No. 1, a series of monographs on the history of plywood manufacturing",Plywood Pioneers Association, 31 March, 1967, www.apawood.org
ASHRAE resource on dew point and wall condensation - see the ASHRAE Fundamentals Handbook, available in many libraries. The following three ASHRAE Handbooks are also available at the InspectAPedia bookstore in the third page of our Insulate-Ventilate section:
2005 ASHRAE Handbook : Fundamentals: Inch-Pound Edition (2005 ASHRAE HANDBOOK : Fundamentals : I-P Edition) (Hardcover), Thomas H. Kuehn (Contributor), R. J. Couvillion (Contributor), John W. Coleman (Contributor), Narasipur Suryanarayana (Contributor), Zahid Ayub (Contributor), Robert Parsons (Author), ISBN-10: 1931862702 or ISBN-13: 978-1931862707
2004 ASHRAE Handbook : Heating, Ventilating, and Air-Conditioning: Systems and Equipment : Inch-Pound Edition (2004 ASHRAE Handbook : HVAC Systems and Equipment : I-P Edition) (Hardcover)
by American Society of Heating, ISBN-10: 1931862478 or ISBN-13: 978-1931862479
"2004 ASHRAE Handbook - HVAC Systems and Equipment The 2004 ASHRAE HandbookHVAC Systems and Equipment discusses various common systems and the equipment (components or assemblies) that comprise them, and describes features and differences. This information helps system designers and operators in selecting and using equipment. Major sections include Air-Conditioning and Heating Systems (chapters on system analysis and selection, air distribution, in-room terminal systems, centralized and decentralized systems, heat pumps, panel heating and cooling, cogeneration and engine-driven systems, heat recovery, steam and hydronic systems, district systems, small forced-air systems, infrared radiant heating, and water heating); Air-Handling Equipment (chapters on duct construction, air distribution, fans, coils, evaporative air-coolers, humidifiers, mechanical and desiccant dehumidification, air cleaners, industrial gas cleaning and air pollution control); Heating Equipment (chapters on automatic fuel-burning equipment, boilers, furnaces, in-space heaters, chimneys and flue vent systems, unit heaters, makeup air units, radiators, and solar equipment); General Components (chapters on compressors, condensers, cooling towers, liquid coolers, liquid-chilling systems, centrifugal pumps, motors and drives, pipes and fittings, valves, heat exchangers, and energy recovery equipment); and Unitary Equipment (chapters on air conditioners and heat pumps, room air conditioners and packaged terminal equipment, and a new chapter on mechanical dehumidifiers and heat pipes)."
1996 Ashrae Handbook Heating, Ventilating, and Air-Conditioning Systems and Equipment: Inch-Pound Edition (Hardcover), ISBN-10: 1883413346 or ISBN-13: 978-1883413347 ,
"The 1996 HVAC Systems and Equipment Handbook is the result of ASHRAE's continuing effort to update, expand and reorganize the Handbook Series. Over a third of the book has been revised and augmented with new chapters on hydronic heating and cooling systems design; fans; unit ventilator; unit heaters; and makeup air units. Extensive changes have been added to chapters on panel heating and cooling; cogeneration systems and engine and turbine drives; applied heat pump and heat recovery systems; humidifiers; desiccant dehumidification and pressure drying equipment, air-heating coils; chimney, gas vent, fireplace systems; cooling towers; centrifugal pumps; and air-to-air energy recovery. Separate I-P and SI editions."
Building Research Council, BRC, nee Small Homes Council, SHC, School of Architecture, University of Illinois at Urbana-Champaign, brc.arch.uiuc.edu. "The Small Homes Council (our original name) was organized in 1944 during the war at the request of the President of the University of Illinois to consider the role of the university in meeting the demand for housing in the United States. Soldiers would be coming home after the war and would be needing good low-cost housing. ... In 1993, the Council became part of the School of Architecture, and since then has been known as the School of Architecture-Building Research Council. ... The Council's researchers answered many critical questions that would affect the quality of the nation's housing stock.
How could homes be designed and built more efficiently?
What kinds of construction and production techniques worked well and which did not?
How did people use different kinds of spaces in their homes?
What roles did community planning, zoning, and interior design play in how neighborhoods worked
Energy Savers: Whole House Systems Approach to Energy Efficient Home Design [copy on file as /interiors/Whole_House_Energy_Efficiency_DOE.pdf ] - U.S. Department of Energy
"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as /interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy
Gypsum Construction Guide, National Gypsum Corporation
Construction Handbook [purchase at Amazon.com] H17, Technical
Folder SA920 and PM2, PM3 and PM4, United States Gypsum Company, 125 South Franklin ST., PO Box 806278, Chicago, IL 60680-4124,
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
Ice Dam Leaks in building attics and roof cavities, how to inspect for evidence of leaks, identify causes, and
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