Kitchen Range Hood CFM & Make-Up Air Sizer
Size kitchen range hood CFM for gas and electric cooktops using HVI width guidance. Evaluate make-up-air requirements under applicable IRC provisions.
Interactive Calculator & Visualizer
Engineering Methodology & Governing Equations
Forced Air Distribution & Dynamic Static Pressure Path
Airflow circulation from return intakes through filtration, blower pressurization, trunk ducting, and room supply registers.
Kitchen Ventilation Sizing & Duct Physics Framework
| Symbol | Variable | Description | Standard Units |
|---|---|---|---|
W_{\text{in}} | Cooktop Width | Nominal cooktop width in inches (converted to linear feet) | Inches |
\text{CFM}_{\text{wall}} | HVI Wall-Mount Baseline | HVI recommendation: 100 CFM per linear foot of cooktop width for wall or under-cabinet hoods | CFM |
\text{CFM}_{\text{island}} | HVI Island-Mount Baseline | HVI recommendation: 150 CFM per linear foot of cooktop width for island hoods | CFM |
\text{BTU}_{\text{total}} | Total Gas Burner Rating | Combined maximum thermal heat output of all gas surface burners | BTU/hr |
\text{CFM}_{\text{gas}} | Gas Rule-of-Thumb Benchmark | Industry field rule of thumb: 100 CFM per 10,000 BTU/hr (verify with appliance manufacturer) | CFM |
\text{IRC M1503.6} | Make-Up Air Review Trigger | Model code threshold where exhaust systems exceeding 400 CFM trigger make-up air review | Threshold (>400 CFM) |
Understanding Kitchen Ventilation, Duct Static Pressure, and Make-Up Air
Effective kitchen ventilation requires balancing thermal plume capture, duct aerodynamic resistance, and room air balance:
- Thermal Plume Capture & Canopy Sizing: Cooking generates thermal plumes containing moisture, grease aerosols, and combustion byproducts. Island hoods lack wall boundaries to direct the convective plume, which is why HVI recommends higher airflow rates (150 CFM/linear ft) and an oversized canopy (typically 3 inches of overhang on each open side).
- Duct Resistance Creates Static Pressure Loss, Not CFM: Longer duct runs, 90ยฐ elbows, and wall caps create friction resistance (measured in inches of water gauge, in. wg), not additional airflow. Range hood blowers must be selected using manufacturer fan performance curves showing delivered CFM at the calculated total external static pressure.
- Make-Up Air Code Review (IRC Section M1503.6): When exhaust airflow exceeds 400 CFM, modern tight building envelopes can experience depressurization. IRC Section M1503.6 and locally adopted mechanical codes typically require an interlocked make-up air supply to prevent backdrafting of combustion appliances and maintain air balance.
Standard Engineering Reference Matrix
| Cooktop Type & Width | Typical Burner Output | HVI Linear Recommendation | Gas Rule-of-Thumb Benchmark | Illustrative Duct Diameter | Make-Up Air Code Review |
|---|---|---|---|---|---|
| 30" Electric / Induction | N/A (Radiant / Induction) | 250 CFM Wall / 375 CFM Island | N/A | 6" Round | โค 400 CFM (Review Local Code) |
| 30" Standard Gas (4 Burners) | 45,000 BTU/hr | 250 CFM Wall / 375 CFM Island | 450 CFM | 7" Round | โ ๏ธ Review Triggered (>400 CFM) |
| 36" Pro-Style Gas (6 Burners) | 60,000 BTU/hr | 300 CFM Wall / 450 CFM Island | 600 CFM | 8" Round | โ ๏ธ Review Triggered (>400 CFM) |
| 48" Commercial-Style Gas | 90,000 BTU/hr | 400 CFM Wall / 600 CFM Island | 900 CFM | 10" Round | โ ๏ธ Review Triggered (>400 CFM) |
| 60" Custom Estate Range | 120,000 BTU/hr | 500 CFM Wall / 750 CFM Island | 1,200 CFM | 10"โ12" Round | โ ๏ธ Review Triggered (>400 CFM) |
Worked Engineering Sizing Example
Scenario: Sizing a kitchen range hood and exhaust duct for a 36-inch pro-style gas cooktop with 6 burners totaling 60,000 BTU/hr, installed on a center kitchen island with a 15-foot duct run and two 90ยฐ elbows.
Calculation Steps:
- Evaluate Sizing Benchmarks: The gas burner rule-of-thumb (60,000 BTU/hr รท 100) indicates 600 CFM. The HVI island linear rate (3.0 ft ร 150 CFM/ft) suggests 450 CFM. A 600 CFM target is selected to handle high-output gas searing.
- Canopy Dimensions: For island cooking, a 42-inch wide hood canopy (3-inch overhang on each side) is recommended to improve plume capture against ambient cross-drafts.
- Calculate Duct Equivalent Length: 15 ft straight + (2 ร 10 ft 90ยฐ elbows) + 25 ft wall cap with damper = 60 equivalent feet.
- Estimate Duct Static Pressure Drop: With an 8-inch rigid metal duct (Area = 0.349 sq ft, Velocity โ 1,719 FPM at 600 CFM), estimated friction is ~0.15 in. wg per 100 ft:
Static Drop โ (0.15 in. wg / 100 ft) ร 60 ft = 0.09 in. wg. - Verify Equipment Fan Curve: Select a range hood rated to deliver at least 600 CFM at ~0.10โ0.20 in. wg external static pressure per manufacturer test data.
- Make-Up Air Code Review: Because 600 CFM exceeds the 400 CFM threshold, review IRC Section M1503.6 and local code requirements for an interlocked make-up air system.
Frequently Asked Questions
How do you size range hood CFM for a gas stove?
When does kitchen exhaust trigger a make-up air code review?
Why do island range hoods require higher CFM than wall hoods?
Governing Research Monograph: Effective Outdoor Air Dilution, Continuous Infiltration Credit, and Multi-Zone Mass-Balance Modeling under ASHRAE 62.2
Report: HL-TR-2026-IAQ04 โข Authors: HVACLogic Research Group, Miad S.
Calculation engines undergo software-level verification against documented equations, reference values, boundary conditions, and automated tests referencing ASHRAE, ACCA, SMACNA, and NIST publications.
โ๏ธ Engineering Reference & Regulatory Disclaimers
Engineering Reference Notice: HVACLogic.org is an independent computational reference and engineering design aid authored by Miad S. Calculations are based on consensus engineering formulations (including ASHRAE, ACCA, and SMACNA publications) and are intended solely for preliminary estimation, parametric analysis, and educational use. HVACLogic does not provide licensed professional engineering services, structural evaluations, or legally binding code determinations.
Professional Review & Permitting Notice: Where the applicable jurisdiction, project type, occupancy classification, permit process, or professional-practice law requires licensed professional review, certification, or a sealed/stamped calculation, the user must obtain that review from an appropriately licensed Professional Engineer (PE) or qualified mechanical contractor. Where a jurisdiction or Authority Having Jurisdiction (AHJ) requires specific calculation software, documentation, or permit submittal forms, users must follow the applicable local requirements.
- Manufacturer installation, operation, and service instructions;
- Applicable refrigerant safety standards (ANSI/ASHRAE 15, ASHRAE 34, and UL 60335-2-40);
- Required technician EPA Section 608 certifications and trade qualifications;
- Applicable mechanical code, fuel gas code (NFPA 54/IFGC), and local Authority Having Jurisdiction (AHJ) requirements; or
- Equipment-specific charging, pressure testing, evacuation, and ventilation procedures.
Manufacturer Data Notice: Generic engineering formulas provide baseline theoretical approximations. Actual equipment performance, expanded cooling/heating capacities at specific outdoor temperatures, sensible-to-total heat ratios, fan airflow curves, and electrical characteristics (MCA/MOP) must be verified against manufacturer technical product data specifications.