HDFreshAir application icon HDFreshAir ASHRAE 62.1 Outdoor Air Calculator

HDFreshAir is a fast, precise desktop tool for calculating minimum outdoor air ventilation requirements in accordance with ASHRAE Standard 62.1 — the industry benchmark for ventilation in commercial and institutional buildings. Whether you are sizing air-handling units, verifying code compliance, or optimizing energy use, HDFreshAir delivers the breathing-zone outdoor airflow numbers you need in seconds.

HDFreshAir implements the ASHRAE 62.1 Ventilation Rate Procedure formula directly:

Vbz = Rp × P + Ra × A

Simply select your ASHRAE standard year, occupancy group, and space type — and HDFreshAir instantly populates the correct per-person outdoor air rate (Rp) and per-area outdoor air rate (Ra) from its built-in lookup table. Enter the number of occupants and the floor area, and the required outdoor airflow is calculated automatically.

KEY FEATURES

  1. Supports ASHRAE 62.1-2010, 62.1-2016, and 62.1-2019 standard years — occupancy categories update automatically for each standard revision.
  2. Complete built-in occupancy table covering all ASHRAE 62.1 space types, from classrooms and offices to sports arenas, restaurants, hotels, and retail environments.
  3. Full IP and SI unit support — toggle between cfm/sq.ft. and L/s/sq.m with a single click; rates are re-fetched from the correct unit column, not converted.
  4. Displays Air Class and applicable ASHRAE notes for each space type so you never have to cross-reference the printed standard.
  5. PDF report generation — produces a cleanly formatted summary of classification, inputs, outdoor air rates, and results, ready to attach to any project submittal.
  6. Clipboard copy — exports all inputs and results as tab-delimited text for pasting directly into spreadsheets or project reports.
  7. HDPsyChart integration — when launched from within HDPsyChart, the Apply button writes the calculated airflow back to the host application automatically.
HDFreshAir occupancy group and airflow results screenshot

OCCUPANCY GROUPS COVERED

HDFreshAir includes every occupancy group and space application defined in ASHRAE 62.1, organized into the same two-level hierarchy used in the standard:

  • Correctional Facilities — cells, day rooms, guard stations, booking/waiting
  • Educational Facilities — daycare, classrooms (all ages), lecture halls, science and art labs, computer labs, music/theater, multi-use assembly, and more
  • Food and Beverage Service — dining rooms, cafeterias, bars, kitchens
  • General Spaces — conference rooms, corridors, storage rooms, break rooms, coffee stations
  • Hotels, Motels, Resorts, Dormitories — bedrooms, lobbies, barracks, multi-purpose assembly, laundry rooms
  • Office Buildings — open office, reception, telephone/data entry, lobbies, breakrooms, storage
  • Miscellaneous Spaces — bank vaults, computer rooms, pharmacies, warehouses, shipping/receiving, transportation waiting, manufacturing, and more
  • Public Assembly Spaces — auditoriums, houses of worship, courtrooms, libraries, museums, lobbies
  • Retail — general sales, mall common areas, barber shops, beauty and nail salons, pet shops, supermarkets, coin-operated laundries
  • Sports and Entertainment — arenas, gymnasiums, spectator areas, pools, dance floors, health clubs, bowling alleys, casinos, game arcades, stages

ASHRAE 62.1 STANDARD YEAR SUPPORT

The occupancy table and space categories in ASHRAE 62.1 change between standard editions. HDFreshAir handles this transparently: selecting a different standard year immediately refreshes the available occupancy groups and sub-categories to match that edition exactly. This makes it straightforward to verify calculations against the specific standard year called out in a project's design criteria or authority-having-jurisdiction requirements.

View more app screenshots here.

System Requirements

  • Windows 10 or Windows 11
  • .NET 8 Runtime (included in installer)
  • 50 MB disk space
  • Standalone or integrated with HDPsyChart

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