A new simpler method for estimating the thermal insulation of a clothing ensemble

The most common method for estimating the basic thermal insulation (I ) of a clothing ensemble is the use of tables with basic thermal insulation values for individual garments (I l ) . Sprague and Munson (1974) found the following relationship between the thermal insulation of an ensemble and the summation of values for the individual garments (EIEli ) : Icl = k ZI li + k,, where k was a constant less than one, and both k and k2 were dependcent on sex (lema~Ie or male clothings) . This equation has since been simplified in ASHRAE Standard 55-81 for thermal environment : IC1 = 0 .82 ZIcli' This paper presents an even simpler' method . Instead of describing the thermal insulation of a single garment by means of the basic thermal insulation (I ), it is proposed to use the effective thermal insulation (Iclu) . The result of the preseni study is then the following relationship : Icl = EIclu' The basic thermal insulation of a clothing ensemble is simply estimated as the sum of the effective insulation for the single garments (EIclu) . Another important advantage of using the proposed method is that when expressing the insulation of a single garment by the effective insulation it is not necedssary to perform the difficult measurement of the increased clothing area factor, f l . The proposed relationship is based on measurements of 70 clothing ensembles in the rangec0 .7-2 .6 clo . INTRODUCTION The thermal insulation of the clothing worn by people is an essential parameter when predicting the influence of the thermal environment on human beings . In cold, neutral, and warm environments, the type of clothing worn will influence the heat exchange between the human body and the environment . This, in turn, influences the acceptability and stress of that environment . In warm environments, clothing is often used to provide protection against the physical environment (dust, sparks, radition) and may, in some cases, increase stress and reduce working time . However, clothing may also be used as protection against heat and increase the working time . In a neutral thermal environment, clothing has a significant influence on the preferred ambient temperature . For example, a chang8 in thermal insulation of 'u 0 .2 clo will change the preferred ambient temperature by x.1 .5 C for a seated person . In cold environments clothing is, in most cases, the only method for making the working conditions tolerable . The thermal insulation of the clothing ensembles must be estimated when evaluating moderate thermal environments according to ASHRAE 55-81 or ISO 7730 (1984) (PMV-PPD index), when Vvaluating hot environments according to ISO/DIS 7933 (1983) (Required Sweat. Rate Index) or ET (Gagge et a1 .1972), and when evaluating cold environments according to the method (IREQ, Required Clothing Insulation) suggested by Holmer (1984) . For this purpose, it is necessary to provide the user of these or similar procedures with methods for the estimation of the thermal insulation . Bjarne W . Olesen, Ph .D ., Laboratory of Heating and Air Conditioning, Technical University of Denmark. 478 ©ASHRAE. All rights reserved. Courtesy copy for SSPC 55 Committee to exclusively use for standards development. May not be distributed, reproduced nor placed on the internet.