ISO 12571:2021

Overview

ISO 12571:2021 specifies laboratory methods to determine the hygroscopic sorption properties of porous building materials and products - key input for hygrothermal performance assessment and moisture modelling. The standard defines two alternative test routes: the desiccator method (reference method) and the climatic chamber method, both used to measure a specimen’s equilibrium moisture content at specified temperature and relative humidity conditions. Sampling is not covered by the standard.

Key Topics and Requirements

• Two test methods
  • Desiccator method (reference): uses saturated salt solutions in desiccators to establish stable relative humidities.
  • Climatic chamber method: uses a controlled chamber to set RH and temperature across the test area.
• Test conditions
  • Reference temperatures: 23 ± 0.5 °C (or 27 ± 0.5 °C for tropical climates).
  • Desiccator RH control: ±2% RH; climatic chamber: ±5% RH and ±2 K temperature uniformity.
• Apparatus & accuracy
  • Balance accuracy: ±0.01% of specimen mass.
  • Drying oven per ISO 12570 for determination of dry mass.
• Specimens
  • Minimum mass 10 g; low-density materials (<300 kg/m3) require minimum area 100 × 100 mm.
  • Minimum three specimens per material.
  • Equilibrium determined by weighing to constant mass (three consecutive weighings ≥24 h apart with <0.1% change).
• Sorption and desorption
  • Sorption curve: moisture uptake at increasing RH stages.
  • Desorption curve: moisture release at decreasing RH; initial point ≥95% RH recommended.
• Reference solutions
  • Standard saturated salts (e.g., MgCl2, NaCl, KNO3) produce commonly used RH points (see annexes for RH values and preparation).

Applications and Who Uses It

ISO 12571:2021 is used by:

• Test laboratories performing material characterization for product data sheets and certification.
• Materials scientists and R&D teams developing moisture-resilient building products (insulation, plasters, composites).
• Building physicists and modelers who need sorption isotherms for hygrothermal simulations and moisture buffering assessments.
• Architects, specifiers, and durability engineers assessing moisture risks, indoor air quality impacts, and long‑term performance.
• Regulators and certification bodies requiring standardized moisture-property data for compliance.

Practical uses include hygrothermal modelling, moisture control strategy design, product selection for damp-prone environments, and evaluation of moisture-related durability.

Related Standards

• ISO 12570 - Drying at elevated temperature to determine moisture content (referenced for oven procedure).
• ISO 9346 - Hygrothermal vocabulary and mass transfer terms used in this standard.