Generator Room Ventilation Calculator
Combustion and cooling air for a standby generator room.
Enter your values
ⓘ Live results
Results
- Combustion air needed
- 375 CFM
- Radiator cooling airflow
- 12,000 CFM
- Design room airflow (larger of the two)
- 12,000 CFM
- Inlet louvre area at 500 FPM
- 24 sq ft
Quick answer
Generator rooms need combustion air (about 2.5 CFM per kW plus radiator airflow), typically dominated by the radiator's own airflow requirement which can be several thousand CFM.
Combustion CFM = 2.5 x kW rating; total CFM often set by radiator fan flow
How to use the Generator Room Ventilation Calculator
- 1Enter the generator's kW rating for combustion air estimate.
- 2Enter the radiator/cooling fan's rated airflow from the spec sheet.
- 3Size room inlet louvres for whichever airflow is larger — usually the radiator.
Worked example
Using the values the calculator loads with:
Inputs
- Generator rating150 kW
- Radiator fan airflow12000 CFM
Results
- Combustion air needed375 CFM
- Radiator cooling airflow12,000 CFM
- Design room airflow (larger of the two)12,000 CFM
- Inlet louvre area at 500 FPM24 sq ft
Frequently asked questions
Why does radiator airflow dominate?
Radiator-cooled gensets move far more air for engine cooling than they need for combustion alone.
What about exhaust heat?
The hot discharge air must have a clear, unobstructed path out, ideally opposite the intake to avoid recirculation.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.