Water vapour permeable
Also known as: Vapour permeable
A material's ability to let water vapour pass while blocking liquid water.
Description
Water vapour permeability (WVP) is the basis of comfortable rainwear. Two metrics: MVTR (g/m2/24h per JIS L 1099, ASTM E96 A/B or ISO 15496 cup) and RET (m2Pa/W per ISO 11092 Hohenstein Skin Model).
Relationship: high MVTR and low RET = good. Rule of thumb: MVTR 20,000 g/m2/24h ≈ RET 6. Principles: micro-porous diffusion (ePTFE), active solution-diffusion (hydrophilic chain), bi-component membranes (e.g. Sympatex®).
Ageing: DWR loss on the outer face causes wet-out and blocked vapour flow even with intact membrane; regular DWR refresh is essential. Skin oils, sunscreen, insect repellents (DEET) may permanently damage membranes. Follow care labels strictly; no fabric softener.
Properties
| Test standard | ISO 11092, JIS L 1099, ISO 15496 |
|---|---|
| Typical values | MVTR 5,000-30,000, RET 3-13 |
| Application | Rain, ski, hiking wear |
Related product categories
Sources & references
2- Wikipedia: Water vapor Wikipedia — Freie Enzyklopädie https://en.wikipedia.org/wiki/Water_vapor_permeability
- ISO 11092 ISO — International Organization for Standardization https://www.iso.org/standard/65962.html
