Waterproof & Breathability Test Spec Builder
Write a testable shell-fabric brief. Keep Ret and MVTR separate, specify durability conditions, and flag the questions a laboratory must resolve.
Why “20K / 20K” is not enough
Waterproofness and water-vapour performance describe different properties. A hydrostatic-head target needs a named method, specimen conditioning, pressure ramp and test endpoint. A breathability result also needs the exact procedure and units. Similar headline values can hide different test conditions.
Ret, MVTR and finished garments
Ret is water-vapour resistance: lower values indicate lower resistance under that method. MVTR is reported as a transmission rate: higher values indicate greater transmission under the stated procedure. This tool does not convert between them or rank results from different methods. A fabric report does not establish finished-garment waterproofness; seams, zips, pockets and construction require separate review.
What to send the laboratory
Agree standard editions, method variants, sampling, conditioning and laundering procedure before testing. Buyer-entered targets are proposed requirements, not recommended performance levels. Ask for results before and after agreed care cycles and identify the exact laminate and production lot.
Sources
ISO 811 hydrostatic pressure test · ISO 11092:2026 · ISO 15496:2018 scope and limitations