ASHRAE 62.1 Outdoor Air Calculator

Calculate breathing-zone and zone outdoor airflow strictly per ASHRAE 62.1 Ventilation Rate Procedure.

Zone Configuration

Ventilation Results

Calculated per ASHRAE Standard 62.1 Table 6-1.
Vbz = Breathing Zone Outdoor Airflow (RpPz + RaAz)
Voz = Zone Outdoor Airflow (Vbz / Ez)

Zone Name Pz Az (ft²) Vbz (cfm) Voz (cfm)
Total System Voz* 0.00 cfm

* Total sum is intended for 100% outdoor air or single-zone systems. Multi-zone recirculating systems require further calculation for System Ventilation Efficiency (Ev) per Section 6.2.5.

Total Zone Outdoor Airflow (Voz)
0.00 cfm

About the ASHRAE 62.1 Outdoor Air Ventilation Calculator

HVAC engineers and mechanical designers can optimize building airflow using our ASHRAE 62.1 outdoor air ventilation calculator. By combining occupancy density rates (Rp) and building area rates (Ra) per zone, the tool calculates the breathing zone outdoor airflow (Vbz). Incorporate zone air distribution effectiveness (Ez) to determine total outdoor airflow requirements, ensuring exceptional indoor air quality while meeting commercial building code standards.

How it works

  1. Select the occupancy category (e.g., office space, classroom, conference room) to determine baseline ventilation rates.
  2. Input the net occupiable floor area and the expected number of occupants for the specific zone.
  3. Select the air distribution configuration to establish the Zone Air Distribution Effectiveness (Ez) multiplier.
  4. Generate the final Zone Outdoor Airflow (Voz) requirement for precise HVAC equipment sizing.

Frequently asked questions

What is the Ventilation Rate Procedure (VRP) in ASHRAE 62.1?

The VRP is a prescriptive design procedure that calculates outdoor air requirements based on the space type, floor area, and expected occupancy. It aims to dilute bioeffluents and building-sourced contaminants to acceptable levels.

What does Zone Air Distribution Effectiveness (Ez) represent?

Ez is a factor that accounts for how effectively ventilation air reaches the breathing zone of the occupants. For example, ceiling supply with ceiling return typically has an Ez of 1.0 during cooling, but can be less efficient during heating.

What is the difference between Vbz and Voz?

Vbz is the Breathing Zone Outdoor Airflow, the raw amount of fresh air required at the occupant level. Voz is the Zone Outdoor Airflow, which is the Vbz adjusted by the distribution effectiveness (Ez) to determine how much air the system must actually supply to the room.

Does ASHRAE 62.1 apply to residential buildings?

No, ASHRAE 62.1 is the standard for ventilation and acceptable indoor air quality in commercial and institutional buildings. Residential buildings are covered by a separate standard, ASHRAE 62.2.

References