Predicted Mean Vote (PMV) is a thermal comfort index that forecasts the average thermal sensation response of occupants on a seven-point scale ranging from -3 (cold) to +3 (hot), with 0 representing thermal neutrality. PMV models the human body’s heat exchange with the environment using measurable parameters. It serves as the foundation for modern thermal comfort standards in ASHRAE 55 and ISO 7730.
Technical Details
PMV calculations integrate six variables: air temperature, mean radiant temperature, relative air speed, relative humidity, metabolic rate, and clothing insulation. The model uses steady-state energy balance equations accounting for sensible heat loss, evaporative cooling, and respiratory heat exchange. PMV accuracy decreases in extreme conditions above 40°C (104°F) or below 10°C (50°F). Studies confirm PMV predictions align with field measurements in approximately 70 percent of cases, with standard deviations around 0.5 on the comfort scale.
Applications in HVAC Design
Design engineers use PMV calculations during system specification to establish appropriate setpoints and verify comfort zone definitions. HVAC simulation software incorporates PMV algorithms to predict occupant satisfaction across varying operating conditions.
Practical Significance
PMV enables data-driven HVAC commissioning and optimization beyond conventional temperature-only approaches, supporting higher occupant satisfaction.