Vapour Permeability in Semi-Permeable Membranes
Uses, Advantages, Markets, and Standards

Semi-permeable membranes are materials engineered to allow certain molecules or vapours - most commonly water vapour, oxygen or CO2 - to pass through while blocking others, such as liquids, dust, or larger chemical compounds. Vapour permeability is a critical characteristic of these membranes, and understanding, measuring, and controlling it is vital across a wide range of industries and applications.

Advantages of Vapour-Permeable Semi-Permeable Membranes

• Moisture Regulation: These membranes allow water vapour to escape while preventing liquid water from entering, reducing condensation and the risk of mould, corrosion, and structural degradation.
• Breathability and Comfort: In clothing and sportswear, high vapour permeability increases wearer comfort by allowing sweat vapour to escape.
• Barrier Protection: In packaging, semi-permeable membranes can preserve freshness, flavour, and stability while controlling the atmosphere inside the packaging.
• Durability and Energy Efficiency: In building applications, breathable membranes reduce trapped moisture within walls and roofs, enhancing thermal insulation efficiency and building lifespan.
• Selective Filtration and Controlled Exchange: In medical and industrial applications, semi-permeable membranes are used to separate gases or manage fluid and vapour transfer precisely.

Market Areas of Use

1. Construction and Building Materials:
• Breather membranes for roofs and façades
• Vapour control layers (VCLs)
• Air and moisture barriers
2. Medical and Healthcare:
• Wound care dressings
• Dialysis membranes
• Drug delivery systems
3. Textiles and Apparel:
• Waterproof breathable clothing
• Footwear linings
• Technical sportswear
4. Food and Pharmaceutical Packaging:
• Modified atmosphere packaging (MAP)
• Breathable films for fresh produce
• Blister packs and sachets
5. Electronics and Automotive:
• Vapour venting membranes for battery packs
• Protective casings with pressure-equalising membranes
6. Agriculture:
• Greenhouse films
• Controlled release fertilisers and pesticide membranes

Relevant Standards
Various international and industry-specific standards govern the testing and performance of semi-permeable membranes with respect to vapour permeability. These include:

• ISO 15106 Series – Methods for determining water vapour transmission rate (WVTR) of plastic films and sheets
• ASTM E96 / E96M – Standard test methods for water vapour transmission of materials using cup methods (desiccant and water methods)
• EN 12572 – Hygrothermal performance of building materials and products – Determination of water vapour transmission properties
• EN 13726-2 – For medical devices and wound dressings – Measurement of moisture vapour permeability
• BS 3177 – British standard method for determining water vapour transmission through flexible sheet materials

Versaperm’s Role
Versaperm specialises in both the manufacture of high-sensitivity instrumentation and the provision of consultancy services to help customers test, understand, and optimise vapour permeability. Its systems are used to measure transmission rates of vapours—including water, oxygen, CO₂, and others—through semi-permeable membranes, ensuring compliance with relevant standards and delivering critical data for R&D, QA, and product design.
Accurate vapour permeability measurement helps manufacturers select materials, predict performance in real-world conditions, and maintain quality and compliance, offering a distinct competitive advantage in innovation-led markets.