Overview
ISO/TS 9124:2025 - Paints and varnishes - Thermal performance of paint films - Determination of solar irradiation penetration ratio with heat flow meter specifies a laboratory measurement method to quantify how much solar energy penetrates paint films used on roofs and exterior walls. The Technical Specification defines the heat flux method using a heat flow meter and solar simulator to derive the paint film solar irradiation penetration ratio (ηp), a direct thermal metric expressed in heat units (W, W/m²).
Key Topics and Requirements
- Measurement principle: Use of a solar simulator to irradiate the paint film and a heat flow meter to measure heat transmitted through the specimen. The penetration ratio ηp is the fraction of incident solar energy that is absorbed and conducted to the interior surface.
- Apparatus composition: Required components include a solar simulator, climatic chamber (external airflow path) and a measuring unit (heat flux meter, sensors, radiometer).
- Sampling and specimen preparation: References ISO 1513, ISO 2808 and related conditioning standards for sample preparation and film thickness control.
- Test conditions and settings: Procedures for setting the external surface heat transfer coefficient, adjusting solar irradiance, and controlling environmental conditions during measurement.
- Verification and calibration: Use of primary standard plates and verification plates; verification methods and environmental checks are specified to ensure reproducibility.
- Measurement and calculation: Parameters to be measured (temperatures, heat flux, irradiance) and the formulas to calculate heat flow rates, penetration ratio and related heat balances.
- Precision and reporting: Guidance on precision, uncertainties and mandatory items for the test report.
- Annexes: Normative and informative annexes cover external heat transfer coefficient settings (Annex A), theoretical heat-balance calculations (Annex B), correlation with solar reflectance (Annex C) and heat flux measurements without solar irradiation (Annex D).
Applications
- Evaluate and compare thermal barrier performance of exterior coatings irrespective of underlying technology (e.g., reflective pigments, insulating additives).
- Input for building energy models, roof and façade thermal performance assessments, and life‑cycle energy calculations.
- Product development and R&D for cool roof coatings, heat‑shielding paints, and energy‑saving exterior finishes.
- Performance verification for specifications, procurement, and certification of thermal paint properties.
Who Should Use This Standard
- Paint and coating manufacturers conducting thermal performance testing and product R&D
- Independent testing laboratories and certification bodies
- Architects, façade engineers and building energy modelers specifying exterior coatings
- Facility managers and sustainability teams assessing retrofit options for roofs and walls
Related Standards
ISO 8301, ISO 22969 (solar reflectance), ISO 1513, ISO 2808, ISO 3270, IEC 60904-9 and other references cited in ISO/TS 9124:2025 for conditioning, instrumentation and radiometric performance.