Heat Recovery Ventilator Calculator
Estimate preliminary HRV airflow from building volume and occupancy, then compare unit capacity, daily energy and operating cost.
Default project preview
107 CFM
ACH airflow
93 CFM
Occupancy airflow
60 CFM
Installed airflow
150 CFM
Building volume
16,000 ft³
Calculator
Build the material order
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Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Conditioned floor area
Enter this project assumption in ft². The current imperial default is 2000 ft².
Average ceiling height
Enter this project assumption in ft. The current imperial default is 8 ft.
Target air changes
Enter this project assumption in ACH. The current imperial default is 0.35 ACH.
Regular occupants
Enter this project assumption in a unitless value. The current imperial default is 4. Minimum: 1.
Outdoor air per person
Enter this project assumption in CFM. The current imperial default is 15 CFM.
Airflow reserve
Enter this project assumption in %. The current imperial default is 15 %. Minimum: 0. Maximum: 50.
Rated airflow per unit
Enter this project assumption in CFM. The current imperial default is 150 CFM.
Electrical input per unit
Enter this project assumption in W. The current imperial default is 120 W.
Operating time
Enter this project assumption in hours/day. The current imperial default is 24 hours/day. Minimum: 0. Maximum: 24.
Electricity price
Enter this project assumption in per kWh. The current imperial default is 0.18 per kWh. Minimum: 0.
How to read the outputs
ACH airflow
0.35 ACH target. Default preview: 93 CFM.
Occupancy airflow
4 occupants. Default preview: 60 CFM.
Installed airflow
rounded full units. Default preview: 150 CFM.
Building volume
area × height. Default preview: 16,000 ft³.
Daily electricity
24 operating hours. Default preview: 2.88 kWh.
Daily energy cost
entered electricity rate. Default preview: $0.52.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
ACH airflow = building volume × target ACH ÷ 60 for CFM, or × ACH for m³/h. Compare it with occupancy airflow, use the larger value, then add reserve.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: July 30, 2026
Use the Heat Recovery Ventilator Calculator to estimate a planning quantity from verified design airflow, sensible efficiency and indoor-outdoor temperature difference. It supports scope comparison, purchasing and operating-cost planning, but it does not select equipment, approve code compliance or replace project-specific design.
Calculation steps
- 1Measure or obtain each design input from the actual project and keep one consistent unit system.
- 2Enter design airflow, sensible efficiency and indoor-outdoor temperature difference using product data or approved design information rather than generic nominal values.
- 3Review the unrounded engineering or usage result before applying allowances, duty cycle, efficiency or tariff assumptions.
- 4Apply each adjustment once, then round only the final purchasing, equipment-count or scheduling output.
Worked numerical example
At 150 cfm with 70% sensible recovery, an entered 30°F indoor-outdoor difference is reduced to roughly 9°F of unrecovered temperature difference in the idealized sensible calculation.
Purchasing and rounding
Choose an HRV from certified airflow and recovery performance at the intended operating point, while also checking fan power, frost strategy and duct resistance.
Interpret the result
The result describes sensible heat recovery under the entered conditions. It does not account for latent transfer, defrost periods, fan heat, leakage or installed duct imbalance.
Page-specific assumptions
- Inputs describe the actual connected system or measured project scope.
- One operating condition, product rating and unit system are used per calculation.
- Allowances and efficiency losses are not already embedded in the entered values.
- Code, health, structural, electrical and hydraulic requirements are verified independently.
Common mistakes
- Using nominal equipment ratings instead of delivered performance at design conditions.
- Mixing instantaneous flow or power with daily or annual energy.
- Applying the same allowance more than once.
- Treating a quantity or cost estimate as equipment selection or professional approval.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
BuildMeter Guides
Understand the measurements and assumptions
Use these visible reference guides before changing project inputs or planning allowances.
FAQ
Heat Recovery Ventilator Calculator questions
Why compare ACH and occupant airflow?+
Volume and occupancy represent different ventilation drivers; the calculator uses the larger entered requirement.
Is rated airflow available after duct losses?+
Actual airflow depends on external static pressure and the unit fan curve, so commissioning and balancing are important.
Does heat-recovery efficiency change airflow sizing?+
Efficiency affects energy recovery, while airflow sizing depends mainly on the ventilation requirement and system resistance.