Overview
ISO 12572:2016/Amd 1:2024 is an important international standard that updates the methodology for assessing the hygrothermal performance of building materials and products. Specifically, it addresses the determination of water vapour transmission properties using the established cup method. This amendment refines the procedures to enhance accuracy and consistency in measuring how building materials interact with moisture vapor under varying environmental conditions.
Developed by ISO Technical Committee ISO/TC 163 in collaboration with the European Committee for Standardization (CEN), this document ensures global alignment for testing materials’ water vapour transmission properties-critical for optimizing building durability, energy efficiency, and indoor air quality.
Key Topics
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Water Vapour Resistance Factor (μ):
The amendment revises subclause 8.6 to clearly define the calculation of the water vapour resistance factor, μ, which quantifies a material’s resistance to water vapour diffusion compared to air.
- μ is calculated using Formula (7), relating water vapour permeability of air and material.
- The Schirmer formula (Formula 8) is introduced to determine the water vapour permeability of air (δₐ) based on mean barometric pressure and temperature.
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Influence of Barometric Pressure:
The amendment highlights that both air and material vapour permeabilities vary with barometric pressure, but μ remains effectively independent of these changes when calculated correctly. Ensuring δₐ corresponds to actual barometric pressure is vital for accurate measurements.
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Use of the Cup Method:
The standard continues to promote the cup method-a widely accepted test technique where a material sample seals a container with controlled humidity conditions inside. Water vapour transmission rates are then measured, enabling assessment of material performance under realistic hygrothermal conditions.
Applications
ISO 12572:2016/Amd 1:2024 applies broadly in the building and construction industry to evaluate moisture-related properties of materials such as:
- Insulation products
- Vapor barriers and retarders
- Wall and roofing assemblies
- Facade materials
- Flooring underlays
By providing reliable data on water vapour transmission, this test supports:
- Building envelope design to prevent moisture accumulation and related damages like mold growth or structural deterioration
- Improved energy efficiency by optimizing vapor control layers
- Compliance with international building codes and green construction standards that demand rigorous moisture management
- Material development and quality assurance for manufacturers aiming to meet performance benchmarks
Related Standards
- ISO 13788: Hygrothermal performance of building components-internal surface temperature to avoid condensation and mould growth
- ISO 8990: Thermal insulation-determination of steady-state thermal transmission properties-guarded hot plate apparatus
- EN 12572: European equivalent standard describing the cup method for water vapour transmission
- ISO/IEC Directives, Part 1 & 2: Governing protocols for developing and maintaining international standards
These complementary standards integrate with ISO 12572 to provide comprehensive guidance for assessing and mitigating hygrothermal risks in building envelopes.
Keywords: ISO 12572:2016/Amd 1:2024, water vapour transmission, hygrothermal performance, building materials, cup method, water vapour resistance factor, barometric pressure, moisture control, building envelope, vapor diffusion, construction standards.
Open preview (PDF)Hygrothermal performance of building materials and products — Determination of water vapour transmission properties — Cup method — Amendment 1