Clothing has many functions including protection and fashion as well as design to provide practical utility (e.g. for holding tools, weapons and accessories) and for cultural reasons to cover modesty. For many clothing ensembles the heat transfer between the body and the environment is complex and not fully understood with many dynamic features. Current methods of considering clothing properties combine this dynamic behaviour into three properties. These are thermal insulation, vapour transfer and ventilation. ISO 9920 and ISO 11079 define the parameter resultant clothing insulation as the actual insulation provided to clothing (including the effects of human movement and wind). Multiple regression equations involving wind and human movement are provided to correct basic and total insulation and evaporative resistance values to resultant values. ISO 9920 also provides a discussion of body posture, chairs, pressure and wet clothing.