Abstract: The "large-scale cold cup" testing apparatus covers the large scale vapor barriers permeability resistance (permeance) determination under "temperature and relative humidity nonequilibrium state," at the service conditions, with test values representing "design data", the quantity of vapor permeated through vapor barrier assembly specimen positioned tightly between a "warm" and a "cold" chamber with controlled air temperatures and relative humidities, being measured by means of the quantity of water, originated of the water vapor condensation on the cold side of the vapor barrier assembly and collected into a measuring graduate tightly connected at the bottom of the cold cup.