Kitchen exhaust calculator: airflow, make-up air and budget

How the calculator works

Exhaust. The hood airflow is the hood length multiplied by the minimum rate per metre from the International Mechanical Code table, which depends on the hood type and the cooking duty. Charcoal and wood fires (extra-heavy duty) are not allowed under back-shelf hoods.

Replacement air. The air a hood removes has to come back. We supply up to 60 % of it as local make-up air in the kitchen and bring at least 40 % from the dining room as transfer air. This split follows the design guide of the Food Service Technology Center, which warns that pushing most of the replacement air through the hood area disturbs capture. The small imbalance also keeps smells on the kitchen side; see kitchen air balance.

Cooling. The dining room must receive at least the outdoor air of ASHRAE 62.1 for restaurant dining (3.8 L/s per person plus 0.9 L/s per m²), and never less than the transfer air it passes to the kitchen; the larger of the two is cooled from Bali design conditions (ASHRAE 2021, Ngurah Rai: 32.5 °C dry bulb, 26.6 °C wet bulb) to 24 °C and 55 %, an enthalpy difference of 32.7 kJ/kg. Diners are counted at 160 W each including food, lighting at 10 W/m²; envelope and sun are an assumption, 40-65 W/m² for a shaded room and 65-90 W/m² for large glazing. One PK is taken as 2.64 kW (9,000 BTU/h).

Power. Air conditioning at an efficiency (EER) of 3.0 W/W, in line with the Indonesian minimum of 2.9 W/W; fans at 2.0 kW per m³/s of air; lighting and sockets at 20 W/m²; electric cooking equipment at a demand factor of 0.7; power factor 0.9 and 25 % spare capacity. The result is rounded up to the next three-phase capacity (breaker rating × 3 × 220 V: 23, 33, 41.5, 53, 66 kVA and so on). Above 197 kVA the connection moves to medium voltage.

Budget. Our indicative Bali ranges from the pricing page: exhaust by hood length, air conditioning per PK (cassette), electrical and Revit design per m², grease trap by seats. Plumbing, water treatment and finishes are quoted after the survey.