Clothing insulation as a biometeorological parameter during rest and exercise

Abstract

A method of direct measurement of the heat and vapor transfer properties of clothing is described when worn in situ by human subjects during rest and exercise. Additional experimental observations were used to verify that a model for predicting F_pcl is reasonably accurate. From the thermal efficiency factor (F_cl), derived from$\bar T$ _s and T_cl measurements, an effective value for I_clo can be determined and thus vapor permeation efficiency (F_pcl) can be predicted. A single coefficient (ψ) that characterizes the boundary environment over the skin surface is the ratio (hF_cl)/(h_eF_pcl) and is determined for any environment in terms of directly observed F_cl factor or clo value and relative air movement concerned. Ultimately,ψ-factor may be used as a key biometeorological parameter to describe any heat balance condition graphically on a psychrometric chart. Its usefulness is also evident in prediction of the probable combination of operative temperature and humidity necessary for thermal acceptable zones, the limits for evaporative regulation, and the zone in which some degree of thermal regulatory failure can be expected.