Ventilation airflow calculator
Add a room, pick the method that fits it — occupancy, residential, public/industrial lookup, or commercial kitchen hood extraction — and get its required airflow. Add as many rooms as your project needs and the total adds up automatically.
How to use this calculator
- Add a room and pick the method that fits it — occupancy-based, residential, a public/industrial lookup, or commercial kitchen hood extraction.
- Enter that method's specific inputs — floor area, occupancy, hood type.
- Add as many rooms as the project needs.
- Read each room's required airflow and the project total.
Need the whole building's supply vs exhaust balance, not just a running total? The Building airflow designer uses the same calculation methods in a dashboard layout that also flags pressurization or depressurization risk and exports a PDF report.
How the required airflow is determined
Ventilation air quantity can be set four different ways depending on the room: by occupancy (people per unit floor area, then a per-person rate), by a fixed minimum for wet rooms in residential buildings, by air-change rate or per-area rate for public and industrial spaces, or — for commercial kitchens — from the actual heat and moisture loads the cooking equipment puts into the room.
Occupancy method
n = A / (m² per person)
PN-83/B-03430: V̇c = n × V̇ [m³/h]
PN-EN 16798-1: V̇c = n × V_L + A × V_A [l/s]
PN-EN 16798-1's VA term accounts for pollutant emission from building materials themselves, scaled by floor area, on top of the per-person VL term — which is why it needs both occupant count and floor area.
Kitchen hood — convective flow
Q_S,K = Q_S × b
d_hydr = 2LB / (L+B)
V̇v-th = k × (Q_S,K × φ)^(1/3) × (h_d + 1.7·d_hydr)^(5/3) × r
V̇v-cap = V̇v-th × a + V̇v-dir
k = 18 m4/3W-1/3h-1 is the method's own empirical constant. φ (simultaneity) and r (source position) reduce the flow for equipment that doesn't all fire at once, or sits against a wall; a (airflow organisation) inflates it to cover disturbance from the room's own supply air.
Equipment heat gains aren't looked up automatically. PN-EN 16282 and ASHRAE publish heat-gain tables for dozens of individual kitchen appliances (fryers, grills, ovens, dishwashers…) — enter your equipment's combined sensible heat output (QS, from its nameplate or a manufacturer datasheet) directly rather than looking it up here.