The most common method for estimating the basic thermal insulation (I_cl) of a clothing ensemble is the use of tables with basic thermal insulation values for individual garments (I_cli). Sprague and Munson (1974) found the following relationship between the thermal insulation of an ensemble and the summation of values for the individual garments (SI_cli ): I_cl = k₁ SI_cli+ k₂ where k₁ was a constant less than one, and both k₁ and k₂ were dependent on sex (female or male clothings). This equation has since been simplified in ASHRAE Standard 55-81 for thermal environment: I_c1 = 0.82 SI_cli.

This paper presents an even simpler method . Instead of describing the thermal insulation of a single garment by means of the basic thermal insulation (SI_cli), it is proposed to use the effective thermal insulation (I_clu) . The result of the present study is then the following relationship: I_cl = SI_clu.

The basic thermal insulation of a clothing ensemble is simply estimated as the sum of the effective insulation for the single garments (SI_clu). 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 necessary to perform the difficult measurement of the increased clothing area factor, f _cl. The proposed relationship is based on measurements of 70 clothing ensembles in the range 0.7-2.6 clo.

Units: SI