ERV / HRV Sizing Calculator
Balanced ventilation airflow for a home.
Enter your values
ⓘ Live results
Results
- Continuous ventilation
- 90 CFM
- Unit size to specify
- 90 CFM
- In L/s
- 42
- Occupants assumed
- 4
- Intermittent equivalent (50% duty)
- 180 CFM
Quick answer
Balanced ventilation is sized at roughly 0.03 CFM per square foot plus 7.5 CFM per occupant.
CFM = 0.03 x sq ft + 7.5 x (bedrooms + 1)
How to use the ERV / HRV Sizing Calculator
- 1Enter conditioned floor area and bedroom count.
- 2Choose a unit rated at or just above the result at 0.4 in wc.
- 3Balance supply and exhaust within 10% at commissioning.
Worked example
Using the values the calculator loads with:
Inputs
- Floor area2000 sq ft
- Bedrooms3
Results
- Continuous ventilation90 CFM
- Unit size to specify90 CFM
- In L/s42
- Occupants assumed4
- Intermittent equivalent (50% duty)180 CFM
Frequently asked questions
ERV or HRV?
ERV transfers moisture as well as heat — better in humid summers or very dry winters.
Can it replace bath fans?
A multi-port ERV can, if each wet room gets a dedicated exhaust pickup.
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.