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 prescribed by ASTM Standard Test Methods for Water Vapor Transmission of Materials (E 96-95). Expanded polystyrene board was chosen as the test material. Nine laboratories completed the measurements according to the dry cup and the wet cup procedures prescribed by the standard. Statistical analyses of the data resulted in the following precision statement for the water vapor permeability:

Dry cup method:

Permeability of material = 3.1E-12 kg m⁻¹ s⁻¹ Pa⁻¹

Repeatability standard deviation (within a laboratory) = 1.6E-1.3 kg m⁻¹ s⁻¹ Pa⁻¹

Reproducibility 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 laboratories) = 4.1E-13 kg m⁻¹ s⁻¹ Pa⁻¹

A specific procedure was uniformly used to analyze the data and to calculate the permeability of the test material from the raw data provided by the participating laboratories. Corrections were made for the resistances offered by the still air layer inside the cup and by the specimen surfaces and for the edge masking details.