Overview
EN ISO 12571:2021 - Hygrothermal performance of building materials and products: Determination of hygroscopic sorption properties (ISO 12571:2021) defines standardized laboratory procedures to measure how porous building materials absorb and desorb moisture from air. The document specifies two alternative test routes - the desiccator method (reference method) and the climatic chamber method - to determine the equilibrium moisture content of a sample at a given temperature and relative humidity. The standard does not cover sampling methods; it focuses on test apparatus, procedures, calculations and reporting.
Key topics and requirements
- Test methods
- Desiccator method: uses desiccators and weighing cups; treated as the reference technique.
- Climatic chamber method: uses controlled-environment chambers to establish humidity and temperature points.
- Objective: determine hygroscopic sorption properties (sorption and desorption curves) and equilibrium moisture content at specified temperature and relative humidity.
- Apparatus and specimen: requirements for desiccators, weighing equipment, climatic chambers and test specimen specification (number and preparation).
- Procedure: stepwise instructions for establishing sorption and desorption curves, control of environmental conditions, and criteria for equilibrium.
- Calculation and reporting: how to calculate moisture content (mass/volume bases), express sorption curves, and prepare a compliant test report.
- Accuracy and control: guidance on measurement error, control of humidity/temperature, and verification of test environment.
- Informative annexes: practical guidance on relative humidities above saturated solutions, preparation of saturated solutions, example procedures, and alternate methods (e.g., glass jar technique).
Applications
- Determining equilibrium moisture content and sorption isotherms for porous building materials (e.g., masonry, insulation, wood-based products, plasters).
- Supplying validated input data for hygrothermal simulation and moisture transport models used in building physics and durability assessments.
- Supporting product development, quality control and performance claims related to moisture buffering, mould risk, and long-term durability.
- Informing specification and selection of materials in damp-prone environments and aiding compliance with building regulations and performance standards.
Who uses this standard
- Laboratory technicians and accredited test labs performing hygroscopic measurements.
- Manufacturers of building materials and components for product characterization and quality assurance.
- Building physicists, hygrothermal modelers and researchers using sorption data for simulations.
- Specifiers, architects and consultants assessing moisture-related performance and material suitability.
Related standards
- ISO 9346 - Vocabulary for hygrothermal mass transfer.
- ISO 12570 - Determination of moisture content by drying at elevated temperature (referenced normative document).
Keywords: EN ISO 12571:2021, hygroscopic sorption properties, hygrothermal performance, desiccator method, climatic chamber method, equilibrium moisture content, sorption curve, building materials.
