Home Ventilation Calculator | ASHRAE 62.2 Baseline

This tool implements the ASHRAE 62.2-2016 total baseline continuous dwelling rate. It adds a floor-area term and a bedroom-based occupancy term. The result is a starting point before permitted infiltration credits, known extra occupants, existing-building adjustments and intermittent-operation factors; it is not automatically the final fan airflow.

This is the fresh outdoor-air requirement, not the recirculated airflow of your cooling or heating equipment. To size the blower or supply ducts that move conditioned air through the home, use the CFM / airflow calculator. For offices, retail, and other non-residential spaces, ventilation follows ASHRAE 62.1 with per-person and per-area rates rather than this formula — see the commercial load calculator for that workflow.

These are unadjusted baseline examples, not equipment selections. Larger houses or higher occupancy can exceed 150 CFM; the formula imposes no residential maximum. Keep fractional values through the calculation and verify the commissioned flow.

• Confusing ventilation CFM with air-handler CFM — outdoor-air ventilation is 50–150 CFM, not the 1,000+ CFM of recirculated supply air.
• Skipping whole-house ventilation in a tight, new home — without it, moisture, CO2, and VOCs accumulate and humidity climbs.
• Overlooking known extra occupants: bedrooms plus one is the baseline proxy, and the adopted standard can require an adjustment for higher occupancy.
• Forgetting local exhaust — kitchen and bathroom exhaust must meet their applicable local requirements; any integration with whole-house ventilation needs a documented design.
• Oversizing the fan and over-ventilating — in humid or cold climates excess outdoor air wastes energy and can raise indoor humidity; meet the rate, do not blow past it.
• Using an unbalanced exhaust fan in a very tight house without a makeup-air or HRV/ERV plan, which can depressurize the home and backdraft combustion appliances.

Envelope leakage varies widely with construction, weather and maintenance. Older houses can leak heavily, while continuous air barriers, taped sheathing and sealed penetrations reduce uncontrolled exchange in newer or retrofitted homes. Neither a building age nor a code label establishes its natural ventilation rate. A blower-door test measures leakage under an imposed pressure; conversion to natural infiltration requires weather, shielding and building information. ACH50 is the air-change rate measured by a blower-door test at a 50-pascal pressure difference, the standard diagnostic used by DOE and by energy raters; lower numbers mean a tighter shell.

A tight shell saves energy, but it also stops removing the contaminants that people and buildings generate every day: water vapor from cooking, bathing, and breathing; carbon dioxide that climbs past 1,000 ppm in occupied bedrooms; and volatile organic compounds (VOCs) off-gassing from furniture, paint, and cleaning products. When natural infiltration falls below the dilution the occupants need, indoor air quality (IAQ) degrades — humidity rises, mold risk grows, and odors linger. That is the gap ASHRAE Standard 62.2 was written to close. It treats fresh-air delivery as a designed mechanical system rather than something the house happens to provide by leaking. The rate this tool returns is small — usually 45 to 150 CFM — for the stated house sizes. Infiltration credit, if used, is a separate adjustment to the total baseline.

ASHRAE 62.2 specifies how much air, not how to move it. Three architectures meet the same CFM target with very different costs and comfort outcomes, and climate is usually the deciding factor.

Exhaust-onlyventilation is the simplest: a quiet, continuously rated bath fan (often an ENERGY STAR–listed model drawing under 10 watts) pulls stale air out, and fresh air enters through the envelope's remaining leaks and trickle vents. It is inexpensive to install but offers no filtration of incoming air and slightly depressurizes the house, which is a concern with atmospheric-vented combustion appliances. Supply-only ventilation runs a fan that pushes filtered outdoor air in, slightly pressurizing the home. This can change pollutant entry paths, but it is not a substitute for radon testing or mitigation — but it pushes that unconditioned air into the living space without tempering it. Balanced systems run matched supply and exhaust fans so the house stays neutral. The premium versions add heat recovery: an HRV (heat-recovery ventilator) transfers sensible heat between the two airstreams, while an ERV (energy-recovery ventilator) transfers both heat and a portion of the moisture. An ERV typically suits hot-humid and cold climates because it limits the latent load the fresh air adds; an HRV suits cold, dry climates where you do not want to retain indoor moisture.

When you select equipment, confirm it can actually deliver the target flow at the static pressure of your duct run — manufacturers publish fan curves, and an HRV/ERV core adds resistance that a bare bath fan does not. The same airflow discipline applies to the air handler that conditions the home: that recirculated airflow is far larger and is sized separately with the CFM / airflow calculator.

ASHRAE 62.2 does not stand alone. It is the ventilation companion to the broader ACCA load-and-equipment workflow: Manual J sizes the heating and cooling loads, Manual S selects the equipment to match them, Manual D designs the duct system, and Manual N covers light commercial. Ventilation airflow from 62.2 is layered on top of that process because outdoor air becomes part of the building's sensible and latent load — every cubic foot of fresh air in summer must be cooled and, in humid climates, dehumidified, which is exactly why heat- and energy-recovery cores pay off.

Code adoption flows through the IECC and the International Residential Code, which reference 62.2 (or an equivalent) and tie required tightness and ventilation to the IECC climate zones. The 0.03 coefficient belongs to the implemented baseline equation; it should not be read as a project-specific leakage allowance. Local adoption determines which edition and adjustments govern your installation. For light-commercial and multifamily common spaces the governing document shifts to ASHRAE 62.1, with its per-person and per-area ventilation rates and an outdoor-air calculation that this residential calculator does not compute — that workflow lives in the commercial load calculator. Pairing the right standard with the right space keeps both the IAQ outcome and the energy penalty defensible.

Using these inputs, the results are baseline continuous ventilation: 84 CFM; area component: 54 CFM; occupancy component: 30 CFM; formula occupancy: 4 people. Defaults are example assumptions, not universal design conditions.

• Do not use this residential equation for a gym or commercial kitchen.
• Do not subtract assumed infiltration without the required measurement and credit procedure.
• Have a ventilation designer check local requirements, combustion interactions, installed airflow and intermittent controls.

Continue with the related calculator for a separate part of the design.

ACCA explanation of ASHRAE 62.2-2016 explains the method or rating limits discussed here. The example inputs are stated scenarios and require project-specific verification.

For residential design, ACCA Manual J, S and D address load calculation, equipment selection and duct design. This calculator does not certify a complete design or code compliance.