Overview
ISO 16535:2019 specifies laboratory procedures for determining the long‑term water absorption by immersion of thermal insulating products for building applications. The standard defines equipment, specimen preparation, conditioning and two principal test approaches: Method 1 - partial immersion and Method 2 - total immersion. Results are based on the change in mass of specimens after a 28‑day immersion period and are intended to simulate long‑term exposure or serve as a relevant laboratory condition for product assessment.
Key Topics and Requirements
- Scope: Applies to thermal insulating products used in buildings; two immersion methods (partial and total).
- Test duration: Long‑term water absorption determined after 28 days (readings at 7 or 14 days optional).
- Specimens:
- Square prisms, sides (200 ± 1) mm, thickness equal to original product thickness.
- At least four specimens if no product standard specifies otherwise.
- Cut without original edges removed; retain skins/facings.
- Conditioning and test environment:
- Standard: (23 ± 5) °C (conditioning at least 6 h). In case of dispute use (23 ± 2) °C and (50 ± 5) % RH.
- Tropical option: (27 ± 5) °C, 65 ± 5 % RH (stated in report).
- Apparatus:
- Balance accurate to 0.1 g.
- Water tank with level control ±2 mm and specimen holders that do not cover >15% of exposed cross‑section.
- Drainage equipment for removing surface water (or methods that deduct initial uptake).
- Methods and variations:
- Method 1 (partial immersion): bottom face (10 ± 2) mm below water level. Two variants: 1A (drainage) and 1B (deduction of initial uptake).
- Method 2 (total immersion): top face (50 ± 2) mm below water level. Variants include 2A (drainage), 2B (deduction) and 2C (Archimedes principle to measure without moving sample).
- Measurement and reporting:
- Mass change measured (m0, m28, and intermediate values where used).
- Calculation methods for absorption by partial or total immersion are defined.
- Test report must state methods, conditioning, temperature, and any tropical conditions.
Applications and Users
ISO 16535:2019 is used by:
- Manufacturers verifying product performance and compliance.
- Test laboratories performing standard water‑uptake testing.
- Specifiers, architects and building engineers assessing moisture sensitivity of insulation for durability and hygrothermal design.
- Regulatory bodies and certification schemes requiring standardized test data.
Practical uses include evaluating suitability of insulation for ground contact, damp environments, exterior facings, product development and quality control.
Related Standards
- ISO 29768 - referenced for determination of linear dimensions of test specimens.
- Relevant product standards or technical specifications for specific insulation types should be consulted for additional requirements or specimen numbers.
Open preview (PDF)Thermal insulating products for building applications — Determination of long-term water absorption by immersion
