PMV (Predicted Mean Vote) is a numerical index that predicts the mean thermal sensation vote of a large group of occupants exposed to a particular thermal environment on a scale from -3 (cold) to +3 (hot). Developed by Fanger in 1970, PMV integrates air temperature, mean radiant temperature, air speed, humidity, metabolic rate, and clothing insulation into a single comfort prediction. PMV values near zero indicate optimal comfort.
Technical Details
PMV calculations use mathematical models of human thermoregulation and energy balance. A PMV of -1 indicates cool conditions; +1 indicates warm conditions. ISO 7730 and ASHRAE 55 define PMV as the basis for comfort standards. PMV has limitations above 40°C (104°F) and below 10°C (50°F) and does not account for acclimatization. Field validation studies show PMV predictions correlate with actual occupant comfort approximately 60 to 80 percent of the time in controlled environments.
Applications in HVAC Design
Design engineers use PMV calculations to verify comfort zones and optimize setpoints. Building energy simulation software incorporates PMV models to predict occupant satisfaction during design phases.
Practical Significance
PMV provides an objective comfort metric to guide HVAC commissioning and system adjustments beyond simple temperature control.