December 2025: New Standard Measures Solar Heat in Paints and Coatings

December 2025 brings a pivotal update for professionals in the paint and colour industries. The International Organization for Standardization (ISO) has published ISO/TS 9124:2025, a comprehensive technical specification that establishes how to assess the thermal performance of paint films through precise measurement of solar irradiation penetration. This new standard provides industry professionals, quality managers, engineers, and procurement specialists with a rigorous and reproducible method to evaluate and compare the heat-shielding capacities of exterior coatings for buildings and outdoor infrastructure.

Overview / Introduction

In the ever-evolving field of architectural coatings and paints, standards compliance ensures reliability, safety, and innovation. Precise measurement of thermal properties is critical as the industry shifts focus toward energy-efficient buildings and comfortable indoor environments. Paint films and varnishes do more than enhance aesthetics—they play a significant role in managing solar energy, building comfort, and even environmental impact.

With energy codes tightening globally, professionals depend on standardized methods to quantify how much solar energy passes through painted surfaces. The new ISO/TS 9124:2025 empowers stakeholders—ranging from building product manufacturers to quality auditors—to select and specify coatings based on validated thermal performance data, ensuring projects meet both regulatory and sustainability goals.

This article provides:

A detailed breakdown of the new standard
Its technical scope and practical requirements
Implementation advice, compliance strategies, and reasons to prioritize adoption
Authoritative links to the official standard at iTeh Standards

Detailed Standards Coverage

ISO/TS 9124:2025 – Paints and Varnishes: Solar Irradiation Penetration by Heat Flow Meter

Paints and varnishes – Thermal performance of paint films – Determination of solar irradiation penetration ratio with heat flow meter

The newly released ISO/TS 9124:2025 offers a trailblazing measurement technique for determining the solar irradiation penetration ratio of exterior paint films. This ratio is vital in understanding how various paint formulations impact the amount of solar energy—essentially heat—that penetrates through surfaces exposed to direct sunlight, such as building roofs, walls, and other outdoor structures.

What does this standard cover?

The specification details a heat flow measurement method using a heat flow meter to quantify how much solar energy passes through painted films applied to typical substrates (e.g., black-painted aluminum plates).
It defines all apparatus requirements, test specimen preparation, environmental conditions, and verification/calibration steps needed to produce reliable, reproducible results.
The method is suitable for any organization manufacturing or specifying solar heat-shielding or energy-efficient paints, especially for buildings, structures, and outdoor equipment.

Key requirements and specifications

Apparatus: Mandates use of a solar simulator (e.g., xenon or metal-halide lamps per IEC 60904-9), climatic chamber for airflow and temperature control, heat flow meter as per ISO 8301, precise thermocouples and a thermopile-type radiometer.
Sample Preparation: Involves preparing test films to rigorous standards (thickness, roughness, color, gloss) on aluminum substrates, with specific paint and substrate characteristics.
Environmental Controls: Testing must be performed in a humidity- and temperature-controlled room (23 ± 2 °C; 50 ± 5% RH) free from contaminants—conditions defined in ISO 3270.
Measurement Principle: Paint film is irradiated in a controlled chamber, the heat passing through is measured via a heat flow meter, isolating the effect of solar irradiation from other thermal influences.
Results: The key metric is the solar irradiation penetration ratio (ηp)—the portion of incident solar heat that penetrates through the paint, with all calculations and reporting methodologies clearly specified.

Who needs to comply?

Paint Manufacturers & Developers: Especially those marketing energy-saving, heat-shield, cool-roof, or thermal-control coatings.
Building Materials Producers: For cladding, panel products, roofing membranes, or any product where exterior thermal performance is a selling point.
Facility and Asset Managers: Evaluating retrofit coatings for energy savings.
Research and Testing Laboratories: Ensuring robust, reproducible measurements for product certifications.
Architects & Specifiers: For projects with sustainable design or thermal comfort targets.

Practical implications for implementation

Adopting this standard allows manufacturers to objectively compare paint products for thermal shielding, making performance claims transparent and defensible.
Product development teams can hone formulations to reduce heat ingress, opening up new opportunities in the growing market for cool roof or passive energy-saving solutions.
Asset owners and specifiers can now require third-party testing and documentation of solar heat performance, reducing risk and supporting green building certifications.

Notable changes (First edition)

This is a first-edition technical specification—there is no previous version. It incorporates body-of-knowledge from related measurement and climatic standards, providing a harmonized test protocol that bridges gaps between paint, building, and energy performance communities.

Key highlights:

Universal method for measuring heat penetration through external paints
Integrates test apparatus, environmental controls, and reporting for reproducibility
Essential for procurement and compliance in sustainable building projects

Access the full standard: View ISO/TS 9124:2025 on iTeh Standards

Industry Impact & Compliance

Business Implications

The introduction of ISO/TS 9124:2025 marks a turning point for businesses at every stage of the paint and coatings supply chain. As regulatory bodies, building owners, and specifiers increasingly demand evidence-backed energy performance, this standard serves as a common language and impartial benchmark.

Adoption delivers several business-critical benefits:

Competitive Edge: Manufacturers who adopt and certify per this standard can differentiate their products with verified data for specifiers.
Market Access: Complying with ISO/TS 9124:2025 can be essential for exporting to regions with green building mandates or for project eligibility under ESG frameworks.
Risk Reduction: Transparent testing reduces the risk of disputes over thermal performance and enables more reliable warranties.
Procurement Clarity: Buyers and specifiers can now insist on independent performance verification when purchasing energy-saving coatings.

Compliance Considerations and Timelines

Transition Periods: While ISO/TS 9124:2025 is new, early adopters will set the benchmark. Regulatory integration may take time but leading firms should prepare now.
Product Labeling: Businesses may wish to update datasheets and marketing claims to reference ISO-conforming results.
Certification & Auditing: Third-party laboratories should align test protocols with the standard to support certification, tender submissions, and market claims.
Documentation: Quality managers must ensure full traceability, from sample prep to reporting, as per the standard’s test section and reporting annexes.

Benefits

Ensures global harmonization in how solar heat performance is measured and communicated
Supports energy efficiency targets and regulatory compliance
Enhances the credibility of product performance claims

Risks of Non-Compliance

Inability to compete in projects requiring proof of heat-shielding performance
Higher risk of product claims being challenged by regulators or clients
Potential exclusion from public tenders or green building projects

Technical Insights

Common Technical Requirements

ISO/TS 9124:2025 brings together a suite of requirements that professionals must integrate into their R&D and QC workflows:

Test Sample Integrity: Substrate and film preparation must mirror real-world application as closely as possible.
Environmental Controls: Precision in laboratory climate is essential; deviations directly affect measurement uncertainty.
Instrumentation Precision: The core of the method is a heat flow meter for quantitative data, demanding strict calibration and verification (using reference plates as detailed in the standard).
Solar Simulator Quality: Light source uniformity and spectral accuracy are vital; Class BBB lamps or better must be used for valid results.

Implementation Best Practices

Setup and Training: Invest in the correct hardware (calibrated heat flow meter, solar simulator, environmental chamber). Train staff on ISO/TS 9124:2025 workflows.
Document Everything: Keep records of all calibration, sample preparation, environmental conditions, and test results. The standard’s reporting template (section 8) ensures consistency.
Inter-laboratory Testing: Participate in proficiency testing where possible to benchmark performance and minimize bias.
Data Integration: Link results from ISO/TS 9124:2025 testing with building simulation models to forecast real-world energy savings.

Testing and Certification Considerations

Reproducibility: Repeat measurements must fall within ±5% for heat flow; unresolved discrepancies must be investigated.
Calibration: Use primary standard plates for apparatus calibration and verification plates to check the system (see Annex A for heat transfer coefficient calibration specifics).
Reporting: The final test report should document all parameters as per clause 8, ensuring end-users or clients can assess product suitability.

Conclusion / Next Steps

With the release of ISO/TS 9124:2025, the paint and colour industries take an essential step toward quantifying and validating the energy-saving potential of their products. Professionals who move quickly to implement this standard—through updated testing, documentation, and training—will be best positioned to meet market demands and regulatory requirements in the era of sustainability and performance transparency.

Key Takeaways:

ISO/TS 9124:2025 sets a benchmark for measuring solar heat penetration through paint and coatings
Full alignment ensures global credibility and smoother regulatory pathways
Early adoption enables superior product positioning and future-proofs against tightening energy codes

Recommendations:

Review your organization’s current testing protocols for alignment with the new ISO standard
Plan investments in lab upgrades, staff training, and third-party certification as needed
Use validated thermal performance data in your product claims and marketing

Explore the full text: ISO/TS 9124:2025 at iTeh Standards

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