Hot Aisle Containment Calculator
Return airflow needed for a contained hot aisle.
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ⓘ Live results
Results
- Required return airflow
- 8,400 CFM
- Containment volume
- 768 cu ft
- Turnover rate
- 656.3 volumes/hr
- Recommended return grille area at 500 FPM
- 16.8 sq ft
Quick answer
Contained hot aisle return airflow should match total rack supply airflow, with volume sized to avoid excess dead space.
Return CFM = supply CFM x 1.0-1.1
How to use the Hot Aisle Containment Calculator
- 1Sum the supply airflow of all racks feeding the hot aisle.
- 2Measure the containment aisle length, width and height.
- 3Size return grilles or ducted returns 5-10% above supply to keep the aisle slightly negative.
Worked example
Using the values the calculator loads with:
Inputs
- Total rack supply airflow8000 CFM
- Aisle length24 ft
- Aisle width4 ft
- Containment height8 ft
Results
- Required return airflow8,400 CFM
- Containment volume768 cu ft
- Turnover rate656.3 volumes/hr
- Recommended return grille area at 500 FPM16.8 sq ft
Frequently asked questions
Why oversize return slightly?
It prevents hot air from leaking around end doors back into the cold aisle.
Cold aisle containment instead?
Use the same supply-matches-demand principle but seal the cold aisle instead.
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.