Overview
ISO 22969:2019 - Paints and varnishes: Determination of solar reflectance - specifies a standardized laboratory method to measure solar reflectance of coating systems. The method uses a spectrophotometer with a wide spectral range (300 nm to 2 500 nm) together with a defined reference global solar radiation spectrum to calculate total solar reflectance (TSR). This standard is applicable to paints and varnishes and provides repeatable results for evaluating how coatings reflect incoming solar energy.
Key topics and requirements
- Measurement range and equipment
- Spectrophotometer with spectrometer covering 300–2 500 nm.
- Use of an integrating sphere and measurement geometry 8°:di or di:8° so specular reflection can be included (see CIE guidance).
- Spectral data
- Spectral reflectance measured routinely at 5 nm intervals across 300–2 500 nm.
- Instruments and reflectance scale should be traceable to national metrology institutes.
- Reference solar spectrum
- Reference global solar radiation is derived using the SMARTS 2.9.5 model with defined parameters: air mass 1.0; aerosol optical depth 0.10; water vapor 1.42 atm‑cm; ozone 0.340 atm‑cm. The standard includes a tabulated reference irradiance (Annex A).
- Calculation
- Total solar reflectance is obtained by spectrally weighting the specimen’s spectral reflectance with the reference global solar irradiance (spectral integration across the wavelength range).
- Test conditions and reporting
- Standard conditioning: (23 ± 2) °C and (50 ± 5) % RH (ISO 3270).
- Test report must reference ISO 22969:2019 and include specimen description, spectrophotometer type, geometry, spectral range and step, measured spectral reflectance, calculated solar reflectance, deviations and test date.
Practical applications and users
- Who uses it
- Paint, coatings and varnish manufacturers for product development and quality control.
- Laboratories performing standardized reflectance testing and certification.
- Architects, building engineers and façade consultants assessing cool-roof coatings and energy-performance measures.
- Environmental and sustainability analysts quantifying cooling energy savings and urban heat island mitigation.
- Why it matters
- Provides a reliable metric to compare coatings’ ability to reflect solar energy - important for energy savings, thermal comfort, roof and façade performance, and reduction of greenhouse gas emissions.
Related standards
- ISO 3270 - Temperatures and humidities for conditioning and testing
- ISO 4618 - Paints and varnishes - Terms and definitions
- CIE 15 guidance on reflectance measurement geometry
- SMARTS (model) reference for generating global solar spectra
Keywords: ISO 22969:2019, solar reflectance, paints and varnishes, spectrophotometer, 300–2500 nm, global solar radiation, SMARTS 2.9.5, integrating sphere, coating systems.
