Predicted mean vote index

ISO EN 7730 standardizes the PMV-PPD index as the method for evaluation of moderate thermal environments. To quantify the degree of comfort, the PMV (predicted mean vote) index gives a value on a 7-point thermal sensation scale -t-3 hot, +2 warm, +1 slightly warm, 0 neutral, -I slightly cool, -2 cool, -3 cold. An equation in the standard calculates the PMV index based on the six factors (clothing, activity, air and mean radiant temperatures, air speed, and humidity). 

Predicted mean vote index (PMV) An index used to predict the mean value of thermal sensation votes of a large group of persons, expressed on a 7-point scale. 

The PMV index predicts the mean value of the thermal preferences of a large group of people exposed to the same environment. But individual votes are scattered around this mean value, and it is useful to predict the number of people likely to feel uncomfortably warm or cool. The PPD (predicted percentage of dissatisfied) index establishes a quantitative prediction of the number of thermally dissatisfied people. The PPD predicts the percentage of a large group of people likely to feel too warm or cool, i.e., voting hot (-t-. , warm (4-2), cool (-2), or cold (-3) on the 7-point thermal sensation scale. 

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