Only when Fanger empirically established the well-known Predicted Mean Vote (PMV) equation, the formulation of these parameters was successfully made [42]. Fanger's Predicted Mean Vote (PMV) index quantifies the degree of discomfort and is expressed on such a psycho-physical scale of hot, warm, slightly warm, neutral, slightly cool, cool and cold. He then introduced the Predicted Percentage Dissatisfied (PPD) index which establishes a quantitative prediction of the percentage of thermally dissatisfied people, obtained from PMV [22].