How should a range hood be vented? A range hood should be ducted outdoors through rigid metal duct with a backdraft damper, move at least 100 cfm when run intermittently, cover the full cooktop, and have makeup air if it can exhaust more than 400 cfm.
Key Takeaways
- The 2015 IRC sets kitchen exhaust at 100 cfm intermittent or 25 cfm continuous (DOE Building America Solution Center).
- 2018 IRC Section M1503.6 requires makeup air for hoods that can exhaust more than 400 cfm (DOE retrofit duct guide).
- DOE says the duct must vent outdoors, “not into an attic, crawlspace, or space between floors” (BASC).
- ENERGY STAR range hoods need at least 2.8 cfm/W and at most 2.0 sones (ENERGY STAR).
- Berkeley Lab measured capture efficiency from under 15% to over 98% across 7 hoods in 2012 (LBNL).
- California hoods ran for 36% of cooking events in houses and 28% in apartments (LBNL, 2020).
What does a range hood actually do?
A range hood is local exhaust: a fan that pulls air from over the cooktop and, when ducted, sends it outdoors. The EPA states that “Using a stove hood with a fan vented to the outdoors greatly reduces exposure to pollutants during cooking.”
Local exhaust removes a pollutant at its source while the fan runs; whole house ventilation exchanges indoor and outdoor air for every room. Our explainer on what ventilation means in HVAC separates the two, and the guide to heat and energy recovery ventilators covers the whole house side.
Bathrooms have their own rules, covered in our bathroom exhaust fan guide.
Ducted or recirculating: which range hood removes pollutants?
A ducted range hood is the type that sends cooking pollutants outdoors. DOE’s Solution Center checklist says protection “is substantially compromised with models that just filter the air and return it to the kitchen,” and its Kitchen Exhaust Fans guide calls filter and return fans “not acceptable.”
| Hood type | Where the air goes | What DOE BASC says |
|---|---|---|
| Ducted wall or under cabinet hood | Outdoors, through a backdraft damper | Discharge outside with a backdraft damper (2015 IRC Section M1505) |
| Recirculating (ductless) hood | Through a filter, back into the kitchen | “Not acceptable” as kitchen exhaust |
| Over the range microwave | Often back into the kitchen | Many are recirculating fans, not exhaust fans |
| Downdraft system | Often back into the kitchen | Listed with microwaves as commonly recirculating |
Berkeley Lab scientist Brett Singer put it plainly in 2018: “If you have a range hood that just recirculates air back into the kitchen, you need to use another exhaust fan” (Berkeley Lab).
How much airflow does a range hood need by code?
Under the 2015 IRC, a kitchen fan run intermittently needs at least 100 cfm and one run continuously needs at least 25 cfm. DOE’s checklist adds that a continuous fan should “provide ≥ 5 ACH (air changes per hour) based on kitchen volume,” a rate its retrofit guide attributes to ASHRAE 62.2-2019.
| Document | Requirement | Applies to |
|---|---|---|
| 2015 IRC (M1504, M1505) | 100 cfm intermittent; 25 cfm continuous | Kitchen exhaust |
| ASHRAE 62.2-2019 | 100 cfm intermittent or 5 ACH by kitchen volume | Kitchen exhaust |
| 2018 IRC M1503.6 | Makeup air above 400 cfm | Kitchen exhaust hoods |
| ENERGY STAR | 2.8 cfm/W minimum; 2.0 sones maximum | Range hoods of 75 W or less |
| DOE BASC checklist | Outlet at least 10 feet from any air inlet | Duct termination |
These are floors, and your jurisdiction may use a different code edition. To check 5 ACH, multiply kitchen length, width and ceiling height, multiply by 5, then divide by 60 for cfm.
When does a large range hood need makeup air?
A range hood that can exhaust more than 400 cfm needs makeup air under Section M1503.6 of the 2018 IRC, as DOE restates it. DOE says the system “will automatically start and operate simultaneously with the exhaust fan and will provide makeup air at a rate equivalent to the exhaust fan rate.”
Safety point: backdrafting
Green Building Advisor, in an article indexed by DOE’s Solution Center, warns that a powerful kitchen fan “may be pulling air down your chimney or water-heater flue.” If a furnace, boiler or water heater vents up a flue, have the house checked before adding a big hood; our boiler replacement guide covers combustion venting. If you smell gas or a carbon monoxide alarm sounds, follow our emergency steps first.
How should range hood ductwork be routed and terminated?
Range hood duct should take the most direct route outdoors in rigid metal and end at least 10 feet from any air inlet. DOE’s retrofit guide says “Metal or plastic flex ducts are prohibited” and joints “must be sealed with either mastic or UL 181 tape.”
The outlet sits “a minimum of 10 feet away or 3 feet above any air inlet and at least 3 feet away from any operable window,” per the same guide. DOE also says the fan must vent outdoors, “not into an attic, crawlspace, or space between floors,” so a kitchen duct is never part of attic ventilation.
How to install or retrofit a ducted range hood
A compliant retrofit follows a fixed order: size, route, seal, terminate, measure. These steps condense DOE’s checklist and retrofit guide.
- Cover the cooktop: the hood “should extend the full width and depth of the cooktop,” centered over the range.
- Meet at least 100 cfm, and plan makeup air if rated capacity exceeds 400 cfm.
- Take the shortest path outdoors with few bends, using the manufacturer’s duct size.
- Install rigid metal duct with a backdraft damper.
- Seal joints with mastic or UL 181 tape, plus wall, ceiling or roof penetrations.
- Terminate with louvers, a screen or a grille, at least 10 feet from any air inlet.
- Measure delivered flow with a flow hood, flow grid or anemometer under ANSI/RESNET/ICC 380-2016.
Mounting height follows the manufacturer’s instructions, and depending on local code a permit may apply. Our checklist for vetting an HVAC contractor covers what to confirm, and our ductwork and airflow guide explains how duct losses are judged.
Why does range hood capture matter more than the cfm number?
Capture efficiency, the share of pollutants a hood pulls in, ranged from under 15% to over 98% across 7 hoods that Berkeley Lab scientists Woody Delp and Brett Singer tested in 2012. Hoods at recommended airflows captured “about 80 percent or greater for back burners but only 60 percent or greater for the oven and 50 percent or greater for front burners.”
The same study found “Open hoods had higher capture efficiency than those with grease screen- and metal-covered bottoms.”
| Cooking location | Capture at HVI recommended airflow | Source |
|---|---|---|
| Back burners | 80% or greater | Berkeley Lab, 2012 |
| Oven | 60% or greater | Berkeley Lab, 2012 |
| Front burners | 50% or greater | Berkeley Lab, 2012 |
How should you run a range hood when cooking with gas?
Turn the hood on every time you cook, favor the back burners, and keep burners adjusted. The EPA says to “Install and use exhaust fans over gas cooking stoves and ranges and keep the burners properly adjusted,” noting that “a persistent yellow-tipped flame, causes increased pollutant emissions” (EPA).
The EPA also says “Never use a gas stove to heat your home.” Singer’s advice is to “ventilate when you cook, and to ventilate more the more you cook”; on low speed over a single back burner, “you’ll typically capture 50 to 70 percent of the pollutants.”
Most people skip the switch. Across 54 single family houses and 17 low-income apartments in California, Berkeley Lab found hoods ran for 36% of cooking events in houses and 28% in apartments. Homes with fuel burning appliances should also work through the safety checks before the heating season.
What goes wrong with range hood ventilation?
The usual failures are a recirculating unit mistaken for exhaust, a duct ending in the attic, a missing backdraft damper, and a large hood with no makeup air. A rated number alone does not confirm the installation, which is why DOE calls for measuring installed flow.
Clamminess is a separate problem, covered in our piece on a house that feels cold but humid.
How we researched this
Research date: September 17, 2026. We opened and cited 9 sources: four DOE Building America Solution Center pages, ENERGY STAR ventilation fan criteria, EPA combustion product guidance and three Lawrence Berkeley National Laboratory publications. Code sections are named as DOE restates them because codes.iccsafe.org blocks automated access.
Excluded: Reddit and homeowner forums, skipped entirely because this topic involves gas combustion and carbon monoxide; contractor blogs and sizing rules of thumb; installed prices (no federal series); and an unverified search snippet on a 150 cfm threshold. Health statements use EPA wording only.
Frequently asked questions
Does a range hood have to vent outside?
DOE’s Building America Solution Center treats outdoor venting as the standard. Its guidance calls recirculating fans that filter air and return it to the room “not acceptable,” and says the hood should discharge outside with a backdraft damper under 2015 IRC Section M1505. Local codes vary.
How many cfm does a range hood need?
The 2015 IRC minimum, as restated by DOE, is 100 cfm for a kitchen fan run intermittently and 25 cfm for one run continuously. ASHRAE 62.2-2019 allows 5 air changes per hour based on kitchen volume. These are minimums, so measure delivered airflow after installation.
Do I need makeup air for a 600 cfm range hood?
Yes, in jurisdictions using the 2018 IRC. Section M1503.6, as restated by DOE, requires makeup air when a range hood can exhaust more than 400 cfm. DOE says the system should start automatically with the fan and supply air at an equivalent rate.
Can I vent a range hood into the attic?
No. DOE’s Solution Center says a kitchen exhaust fan must vent directly outdoors, not into an attic, crawlspace, or space between floors. DOE’s retrofit guide puts the outlet at least 10 feet from any air inlet, or 3 feet above it, and 3 feet from an operable window.
Can I use flexible duct for a range hood?
No. DOE’s Kitchen Exhaust Retrofit Duct Guide calls for rigid metal duct, such as galvanized or stainless steel, and says metal or plastic flex ducts are prohibited. Every joint must be sealed with mastic or UL 181 tape, and duct size follows the manufacturer’s instructions.
Is there an ENERGY STAR range hood rating?
Yes. Range hoods fall under ENERGY STAR’s Ventilation Fans category. For range hoods of 75 W or less, the key product criteria set a minimum efficacy of 2.8 cfm per watt and a maximum sound level of 2.0 sones, using HVI test procedures.
Which burners should I use with a range hood?
Use the back burners when you can. Berkeley Lab’s 2012 test of 7 hoods found that hoods at recommended airflows captured about 80 percent or greater of back burner pollutants but only 50 percent or greater from front burners. Researcher Brett Singer says almost any hood works better over the back burners.
Sources
- U.S. Department of Energy, Building America Solution Center. “Kitchen Exhaust Fan.” https://basc.pnnl.gov/home-improvement-expert/checklists/kitchen-exhaust-fan. Accessed September 2026.
- U.S. Department of Energy, Building America Solution Center. “Kitchen Exhaust Fans.” https://basc.pnnl.gov/resource-guides/kitchen-exhaust-fans. Accessed September 2026.
- U.S. Department of Energy, Building America Solution Center. “Kitchen Exhaust Retrofit Duct Guide.” https://basc.pnnl.gov/resource-guides/kitchen-exhaust-retrofit-duct-guide. Accessed September 2026.
- U.S. Department of Energy, Building America Solution Center. “Makeup Air for Range Hoods.” https://basc.pnnl.gov/library/makeup-air-range-hoods. Accessed September 2026.
- ENERGY STAR. “Ventilation Fans Key Product Criteria.” https://www.energystar.gov/products/ventilation_fans/key_product_criteria. Accessed September 2026.
- U.S. Environmental Protection Agency. “Sources of Combustion Products.” https://www.epa.gov/indoor-air-quality-iaq/sources-combustion-products. Accessed September 2026.
- Lawrence Berkeley National Laboratory. “Berkeley Lab Study Assesses Residential Cooking Exhaust Hoods’ Ability to Vent Pollutants.” https://newscenter.lbl.gov/2012/05/30/berkeley-lab-study-assesses-residential-cooking-exhaust-hoods-ability-to-vent-pollutants/. Accessed September 2026.
- Lawrence Berkeley National Laboratory. “Factors Impacting Range Hood Use in California Houses and Low-Income Apartments.” https://indoor.lbl.gov/publications/factors-impacting-range-hood-use. Accessed September 2026.
- Lawrence Berkeley National Laboratory. “Range Hood Advice from Indoor Air Quality Researcher.” https://indoor.lbl.gov/news/article/range-hood-advice-indoor-air-quality. Accessed September 2026.
Leave a Reply