ISO 24353:2008

Overview

ISO 24353:2008 - "Hygrothermal performance of building materials and products - Determination of moisture adsorption/desorption properties in response to humidity variation" - specifies a laboratory test method to quantify how building materials adsorb and desorb moisture when exposed to changes in relative humidity. The standard defines adsorption/desorption content, rates, and adsorption/desorption efficiency (mass change per unit surface area) for single-cycle and cyclic exposures. Test conditions, specimen preparation and measurement procedures are described to ensure repeatable hygrothermal performance data.

Key topics and technical requirements

• Scope: Measure moisture adsorption/desorption response of building materials to stepwise humidity changes; single-cycle and multi-cycle tests (including specific reference to fourth-cycle values).
• Specimens: Representative pieces, size 100 × 100 mm to 250 × 250 mm, thickness equal to the product; one specimen per test condition.
• Preconditioning: Bring specimen to constant mass (increase < 0.01 g in 24 h) at specified RH before testing.
• Test apparatus:
  • Electronic balance: ±0.01 g resolution for specimens ≤ 6 kg (±0.1 g allowed for heavier specimens).
  • Moisture-proof box with programmable temperature/humidity control, thermometer (±0.1 °C) and hygrometer (measurement capability ±2 %), humidifier using water vapour (no ultrasonic spraying).
  • Windscreen and fan to control airflow; air flow adjusted to achieve water vapour surface resistance = (13.3 ± 1.3) m·h·Pa/µg.
  • Salt-saturated solutions may be used for RH control (see Annex B).
• Test procedure:
  • Typical test temperature (23 ± 0.5) °C.
  • Typical RH step combinations (Table 1): Low (30→55→30 %), Middle (50→75→50 %), High (70→95→70 %); other values allowed as needed.
  • Single-cycle: maintain Step 1 RH for 12 h, then Step 2 RH for 12 h; record mass at 10-minute intervals.
  • Calculations: adsorption/desorption content per unit area, rates, cycle-to-cycle comparisons, fourth-cycle metrics; reporting requirements specified.

Applications and users

ISO 24353 is used to evaluate materials intended to regulate indoor humidity or moderate RH fluctuations:

• Building product manufacturers and R&D labs assessing hygrothermal properties
• Independent testing laboratories and certification bodies
• Architects, specifiers and façade engineers selecting moisture-buffering finishes
• Museum conservators and archival facility designers evaluating climate control strategies
• HVAC and indoor air quality consultants designing passive humidity-control systems

Practical outcomes include material selection for humidity buffering, comparison of moisture-buffering efficiency, and data for hygrothermal modeling of indoor environments.

Related standards

• ISO 12571:2000 - Hygrothermal performance - Determination of hygroscopic sorption properties
• ISO 12572:2001 - Hygrothermal performance - Determination of water vapour transmission properties

Keywords: ISO 24353, hygrothermal performance, moisture adsorption, desorption properties, building materials, relative humidity, adsorption/desorption efficiency, water vapour surface resistance.