In the international standard (ISO 11079) a method is described for calculation of the clothing insulation requirements for given climate conditions. The required insulation value (or index IREQ) is expressed in clo units or in m2°C/W (1 clo=0.155 m2°C/W).
Also described in ISO 11079 is a method for calculation of the combined cooling effect of wind and temperature - the Wind Chill Temperature. It is similar to the old Wind Chill Index.
ISO 7730 describes a method for evaluation of moderate thermal environments and conditions for thermal comfort. The PMV index indicate the thermal sensation vote of people exposed to the actual conditions. PPD gives the percentage of the exposed people that would feel dissatisfied with the conditions.