Water vapor transmission rate, usually measured at 100% relative humidity, expressed in grams/100 square inches/24 hours, (or grams/square meter/24 Hrs.) See MVTR.

Abbreviation for water vapor transmission rate.

Water Vapor Transmission Rate. The rate that water penetrates through the wall or barrier of an enclosure, usually given in g/(m2 x day) or g/(in2 x day).