🔥 Hood Exhaust Airflow
💨 Grease Duct Velocity
Sizing Breakdown
Full Calculation Table
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How to Use the Restaurant HVAC Calculator
Choose the exhaust hood duty classification that matches your kitchen's cooking equipment. Heavy-duty appliances like charbroilers need significantly more exhaust airflow than light-duty ovens or steamers.
Enter the total linear length of exhaust hood over the cookline and the dining area square footage for the comfort cooling calculation.
Enter expected dining seat count and the winter outdoor design temperature, used to estimate makeup air tempering energy.
Click Calculate Restaurant HVAC to see hood exhaust airflow, makeup air requirement, grease duct velocity, and dining area cooling load.
Understanding Restaurant HVAC Sizing
Restaurant HVAC design splits into two largely independent problems: exhausting and replacing air around the cookline, and providing comfort cooling and heating for the dining room. Kitchen exhaust hood sizing follows fire and life safety code requirements tied to cooking equipment type, including CSA B149.1 for any gas-fired cooking equipment on the line, while dining area sizing follows standard occupancy-driven comfort cooling principles similar to the commercial load calculator.
Hood Duty Classification Drives Exhaust Airflow
Exhaust hood airflow requirements scale with the heat and grease-laden vapor produced by the equipment underneath. Heavy-duty equipment like charbroilers and solid fuel cooking needs the highest exhaust rate per linear foot of hood, medium-duty griddles and fryers need a moderate rate, and light-duty equipment like ovens and steamers needs considerably less. Always confirm the specific rate against the hood manufacturer's listing and the authority having jurisdiction, since local fire code amendments vary across Canadian provinces.
Makeup Air Replaces What the Hood Removes
A kitchen exhaust hood pulling several thousand CFM out of the building creates significant negative pressure unless that air gets replaced. Makeup air units supply 80 to 100 percent of the exhaust airflow, tempered close to room temperature so the makeup air doesn't create uncomfortable drafts or cold spots near the cookline. In Canadian winters, tempering this volume of outdoor air against your city's winter design temperature, available from the design temperature lookup, represents a substantial heating load that needs its own dedicated calculation, separate from the building's general heating system.
Grease Duct Sizing and Minimum Velocity
Grease exhaust ductwork needs enough velocity to keep grease particles airborne and moving toward the exhaust fan, typically a minimum of 1,500 feet per minute, though some jurisdictions require higher. Undersized duct area at a given exhaust CFM increases velocity and pressure drop, while oversized duct area risks grease settling inside the duct, a genuine fire hazard that NFPA 96-style cleaning and inspection programs exist specifically to manage.
Dining Room Cooling Is a Separate Calculation
The dining room's cooling load comes primarily from occupant heat gain, lighting, and building envelope loads rather than cooking equipment, since a well-designed hood captures most cooking heat before it reaches the dining space. Seat count and expected turnover rate drive occupancy load more than square footage alone, a per-person basis the CFM per person calculator also uses for the dining room's ventilation requirement, and this calculator applies a standard occupant sensible and latent heat allowance per seat. Pair this with the DOAS calculator if the dining room uses a dedicated outdoor air system for ventilation.
Frequently Asked Questions
Makeup air should replace 80 to 100 percent of the total exhaust airflow to prevent the kitchen from running under excessive negative pressure, which can pull conditioned dining room air into the kitchen or cause the hood to lose capture efficiency. Many jurisdictions require at least 80 percent makeup air with the remainder made up through transfer air from adjacent spaces.
A standard canopy hood over grease-producing appliances like griddles, fryers, and charbroilers typically needs 300 to 400 CFM per linear foot of hood, while an eyebrow or backshelf hood over lighter equipment often uses less. The specific rate depends on hood style, duty classification, and local code requirements, so always confirm against the hood manufacturer's listed rating.
Grease exhaust ductwork typically needs a minimum velocity of 1,500 feet per minute to keep grease particles suspended and moving toward the exhaust fan rather than settling and accumulating inside the duct. Some jurisdictions require up to 1,800 to 2,000 feet per minute depending on the specific code adopted, so confirm the local requirement before finalizing duct sizing.
Kitchen exhaust hoods remove most cooking-generated heat directly through the hood, so the kitchen space itself often needs less mechanical cooling than its raw equipment heat gain would suggest, while the dining room has an entirely separate occupancy-driven load with no exhaust hood offsetting it. Treating the two spaces as one combined load typically results in inaccurate sizing for both zones. See the commercial load calculator for general zone load methodology.
Related HVAC Tools
General makeup air unit sizing
Dining room cooling load basis
Dining room ventilation option
Similar occupancy-driven space
General duct velocity reference
Common dining room system type