Common clothing area factor estimation equations are inaccurate for highly insulating (I>2 clo) and non-western loose-fitting clothing ensembles.

The aim of this study was to evaluate the equations for calculating the clothing area factor (f) used in the standards based on data sets of clothing ensembles, that are meant to provide thermal comfort over a wide range of climatic conditions from hot summer days to extremely cold winter. Over 10 equations for f calculations were selected from the international standards and the literature. At first a theoretical comparison based on a range of insulation values was performed. Then the data sets were used to compare the equations and measurements on real clothing systems. Most of the f calculation equations do give reasonably good results for western type and industrial clothing with basic insulation (I) up to 1.5 clo. Above the I of 2 clo, the error in the calculations based on traditional equations increases considerably and they overestimate f. Some new equations were suggested for modern clothing systems. Oppositely, for non-western clothing (for hot climate), the available equations did give good match only for very light clothing sets and commonly underestimated the real f. For such sets and and fashion clothes their own equations maybe needed, that count for various design aspects, e.g. fit, draping etc.