INTERLABORATORY COMPARISON OF THE ASTM STANDARD TEST METHODS FOR WATER-VAPOR TRANSMISSION OF MATERIALS (E-96-95)

An interlaboratory comparison was initiated by the ASTM C16 Committee on Thermal Insulation to determine the precision of the test method pr escribed by ASTM Standard Test Methods for Water Vapor Transmission of Materials (E 96-95). Expanded poly styrene board was chosen as the te st material. Nine laboratories completed the measurements according to the dry cup and the wet cup procedures prescribed by the standard. St atistical analyses of the data resulted in the following precision sta tement for the water vapor permeability: Dry cup method: Permeability of material = 3.1E-12 kg m(-1) s(-1) Pa-1 Repeatability standard devia tion (within a laboratory) = 1.6E-13 kg m(-1) s(-1) Pa-1 Reproducibili ty standard deviation (between laboratories) = 4.7E-13 kg m(-1) s(-1) Pa-1 Wet cup method: Permeability of material = 3.4E-12 kg m(-1) s(-1) Pa-1 Repeatability standard deviation (within a laboratory) = 1.7E-13 kg m(-1) s(-1) Pa-1 Reproducibility standard deviation (between labor atories) = 4.1E-13 kg m(-1) s(-1) Pa-1 A specific procedure was unifor mly used to analyze the data and to calculate the permeability of the test material from the raw data provided by the participating laborato ries. Corrections were made for the resistances offered by the still a ir layer inside the cup and by the specimen surfaces and for the edge masking details.