Make-Up Air, Air Changes and Kitchen Exhaust

Whatever a kitchen exhausts has to come back in. These calculators show the air balance behind a make-up air unit, the heating load of the incoming air, the air changes per hour of a room, and the airflow figures that public guides give for home kitchen exhaust fans and range hoods. Each page shows its formula and where its numbers come from, and marks example values as examples. Results are estimates to check against the equipment makers’ data and your local requirements.

Tools in this group

• Air Changes per Hour Calculator — Enter the room size and the airflow to see the air changes per hour, or type a target ACH to see the airflow needed, plus the time to clear the air.
• Ducted vs Ductless Range Hood — Say whether you can run a duct, what you cook on and how you cook to see which range hood type fits, and compare the two side by side.
• Heated Make Up Air Unit Calculator — Enter the airflow, the outdoor and supply temperatures, the efficiency and the gas heating value to see the load in Btu/h and kW, the burner input and the gas flow.
• Kitchen Exhaust Fan Size Calculator — Enter the kitchen size, cooktop width and fuel to compare the cfm from three published methods and see the largest.
• Make Up Air for a Range Hood — Enter your range hood airflow to see whether it is above the 400 cfm figure the cited text names, the make-up air to supply and the duct size.
• Make Up Air Unit for Kitchen Hood — Type the exhaust of the hood and other fans and the supply already in place to see the make-up air in cfm, a rounded unit size and the pressure left in the building.
• Range Hood CFM Calculator — Enter the cooktop and the duct run to see the target cfm, the duct pressure and the rated cfm to look for after the hood is derated.
• Range Hood Height Above Stove — Pick the cooktop and hood style to see how high the bottom of the hood goes above the cooktop, how wide it should be, and check a height you already have.