A cup method was used to measure water-vapour transmission in 10 common building materials. The materials included sugar pine, sturdy-brace fibreboard, fibreboard sheathing, particleboard, exterior grade plywood, plain gypsum board, kraft paper, waferboard siding, vinyl-covered gypsum board, and foam core sheathing. For each material, a series of cup measurements was conducted, and the permeability (or permeance) was plotted as a function of the mean relative humidity across the specimen. Separate measurements, carried out at 24 deg C (75 deg F) and 7 deg C (44 deg F), indicated that temperature has an insignificant effect on permeability. The permeability measurements were compared with other measurements reported in the literature, and the agreement was good in most cases.

KEYWORDS: water vapour permeability, measuring, buildings, materials, wood, plywoods, wood particle boards, fibre building boards, gypsum plasterboard, boards, comparing, relative humidity, temperature, adsorption