ISO 23327:2021

Overview

ISO 23327:2021 - Hygrothermal performance of building materials and products - specifies a laboratory test method for determining moisture adsorption/desorption behaviour of building materials exposed to periodic temperature variation. The standard defines specimen preparation, a sealed-box test apparatus, temperature cycling (imitating a sine wave), measurement procedures and calibration for vapour leakage. ISO 23327 is used to quantify how materials buffer indoor moisture when temperatures fluctuate.

Key topics and requirements

• Specimen size and preparation
  • Standard specimen: 100 mm × 100 mm; thickness normally equals product thickness (upper limit 20 mm).
  • Side surfaces are damp-proofed; specimen cured to constant mass (increase ≤ 0.1 g per 24 h) at 23 °C / 50% RH (or 27 °C for tropical conditions).
• Test apparatus
  • Core components: sealed box, box/chamber with thermostat, thermometer and hygrometer.
  • Example sealed-box internal dimensions for a 100×100 mm specimen: 300 × 300 × 400 mm; measurement point 150 mm above specimen surface.
  • Thermal insulation: specimen insulated except test face; insulation thickness 100 mm, thermal conductivity ≤ 0.04 W·m⁻¹·K⁻¹.
• Temperature cycling
  • Box/chamber temperature varied to approximate a sine wave with amplitude 7.5 °C and 24 h period, repeated 4 cycles (example); controller accuracy ±0.5 °C.
• Measurements and instruments
  • Thermometer precision ±0.1 °C; hygrometer precision ±2%. Temperature and RH in sealed box measured at 10-minute intervals (reported to 0.1 °C and 0.1% RH).
• Calibration and leakage
  • Sealed box must be calibrated for water vapour leakage before testing (Clause 8) and meet the tolerance for leakage specified in the standard.
• Reporting
  • Test report must include specimen details, conditioning, temperature cycle, measured humidity/temperature records and calculated moisture-adsorption/desorption results.

Applications and users

ISO 23327:2021 is practical for:

• Building-material manufacturers assessing moisture buffering capacity.
• Independent test laboratories performing hygrothermal characterization.
• Building physicists and researchers modeling indoor humidity dynamics and moisture buffering by materials.
• Product certification and specification processes where hygrothermal performance influences durability, indoor air quality and thermal comfort.

Keywords: ISO 23327:2021, hygrothermal performance, moisture adsorption/desorption, building materials, sealed box test, temperature cycling, moisture buffering.

Related standards

• Normative reference: ISO 9346 (Hygrothermal performance - physical quantities for mass transfer - vocabulary).