Indoor Environmental Quality
Ventilation and thermal comfort
Know ASHRAE Standard 62.1 (ventilation rate procedure and IAQ procedure) and Standard 55 (thermal comfort, PMV/PPD, operative temperature, air speed, clothing and metabolic rates). Distinguish ventilation rate (cfm/person or per area) from air-change rate (ACH). Understand demand-controlled ventilation using CO₂ as a proxy for occupancy - CO₂ indicates ventilation adequacy, not contaminant safety.
Contaminants, moisture, and acoustics
Concepts: source control > dilution > filtration; MERV ratings and pressure drop; outdoor air economizers and their IAQ trade-offs; moisture management to prevent mold; acoustic comfort (NC/RC ratings, background noise). Recognize VOC and formaldehyde off-gassing from materials and the value of flush-out and low-emitting materials.
Traps
- Treating CO₂ as a pollutant rather than a ventilation indicator.
- Confusing Standard 55 (comfort) with Standard 62.1 (ventilation).
- Ignoring filter pressure drop in fan energy and MERV vs. efficiency trade-offs.
- Forgetting that economizer operation can introduce outdoor contaminants or humidity.
- Applying comfort limits without considering air speed and radiant asymmetry.
Worked example
A 2,000 ft² classroom with 30 occupants: using a per-person rate of 10 cfm/person plus 0.06 cfm/ft² area (illustrative values - verify against the current standard table), supply = 30×10 + 2,000×0.06 = 300 + 120 = 420 cfm. If CO₂ rises well above outdoor plus ~700 ppm, ventilation is likely inadequate; adjust DCV setpoint or airflow.