ASHRAE 62.1

HVAKR implements ASHRAE Standard 62.1 - Ventilation for Acceptable Indoor Air Quality using the Ventilation Rate Procedure.

Standard Overview

ASHRAE 62.1 establishes minimum ventilation rates to maintain acceptable indoor air quality:

Applies to:

For each breathing zone:

Vbz = Rp × Pz + Ra × Az

Where:

Adjust for distribution effectiveness:

Voz = Vbz / Ez

Where:

Each system’s outdoor air requirement follows the central unit’s Outside Air method, set in System Design > Configuration:

Sum of Spaces — HVAKR sums the zone outdoor airflows across the spaces the system serves:
```
Vot = Σ Voz
```
Multi-Zone — HVAKR applies the ASHRAE 62.1 multi-zone equation. It divides the uncorrected outdoor air intake Vou (which applies the occupancy diversity D to the people component) by a system ventilation efficiency Ev, so the corrected intake can exceed the simple sum:
```
Vou = D × Σ(Rp × Pz) + Σ(Ra × Az) + Σ Vach + Σ Vcust
Vot = Vou / Ev
```
Ev defaults to 0.75 and drops to 0.88 × D + 0.22 when occupancy diversity falls below 0.6. Each space is counted once — through its breathing-zone rate (Rp, Ra), an air-change minimum (Vach) where air changes govern, or a space-level custom requirement (Vcust) — so the three sums cover disjoint sets of spaces.

Where:

See Ventilation for the full system-outdoor-air treatment, including the fixed-fraction Percent and Custom methods.

HVAKR includes all rates from Table 6.2.2.1:

When occupancy isn’t specified, use Table 6.2.2.1 defaults.

Ez values based on supply configuration:

Configuration	Ez
Ceiling supply, ceiling return	1.0
Ceiling supply, floor return	1.0
Floor supply, ceiling return	1.2
Floor supply, floor return	1.0
Stratified/displacement systems with high ceiling return	1.2–1.5
Personalized ventilation systems	1.2–1.5

Most common configuration:

Minimum exhaust for specific spaces:

Exhaust can be satisfied by:

HVAKR automatically: