Glossary
PMV
Plain-Language Definition
Predicted Mean Vote — a thermal comfort index that predicts the average comfort perception of a large group of people on a 7-point scale from -3 (cold) to +3 (hot), with 0 being neutral/comfortable.
Technical Context
PMV considers six factors: air temperature, radiant temperature, air velocity, humidity, metabolic rate (activity), and clothing insulation. ASHRAE 55 recommends PMV between -0.5 and +0.5 for acceptable comfort (PPD <10%). PMV is calculated using the Fanger comfort equation and is used in HVAC design and WELL certification.
Why It Matters
PMV provides an objective measure of thermal comfort beyond simple temperature. A room at 24°C may be uncomfortable if humidity is 80% or air velocity is zero. PMV-based HVAC control optimises both comfort and energy — avoiding the common problem of overcooling to 18°C.
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