Work out moisture barrier requirement instantly with clear inputs, formula shown and shareable results.
The barrier requirement follows from the moisture budget: allowable water gain divided by shelf life days gives grams per day, and dividing by pack surface area gives the maximum water vapour transmission rate the laminate may have. WVTR is quoted at a stated temperature and humidity, so the specification must state those conditions.
Barrier requirement
Water allowed = product weight x allowable gain %; max WVTR = water allowed / (days x pack area)
Around 5-15 g/m2/day for PE at 38 C and 90% RH, 1-5 for metallised film, 0.1-0.5 for high-barrier coated films and effectively zero for aluminium foil above 9 micron.
Often more than the film. A pack with excellent film but a poor seal or a leaking closure fails long before the barrier calculation predicts, so integrity testing is essential.