ASTM E1175-87(2022)

Overview

ASTM E1175-87(2022) - Standard Test Method for Determining Solar or Photopic Reflectance, Transmittance, and Absorptance of Materials Using a Large Diameter Integrating Sphere provides a comprehensive methodology for measuring the optical properties of diverse materials. Unlike conventional spectrophotometric methods, which are often limited to flat, homogeneous, and isotropic specimens, this standard is specifically designed to accurately characterize spatially nonuniform, patterned, or textured materials of various sizes and shapes. By using a large diameter integrating sphere, this approach ensures that the reflectance, transmittance, and absorptance measurements realistically represent the average behavior of the entire sample surface.

Key Topics

• Accurate Measurement of Optical Properties: The standard describes how to determine absolute total solar or photopic reflectance, transmittance, and absorptance, addressing limitations of traditional techniques for nonhomogeneous samples.
• Large Diameter Integrating Spheres: Use of large integrating spheres enables area-averaged measurement, integrating out local variations and nonisotropic characteristics in the specimen.
• Applicability to Complex Materials: Suitable for both specular and diffuse materials, as well as opaque and semitransparent samples, including:
  • Corrugated fiber-reinforced plastics
  • Textured or composite transparent and translucent materials
  • Heavily patterned or woven materials (e.g., window blinds, draperies)
• Multifunctional & Monofunctional Sphere Options: The method allows measurements using either spheres dedicated to transmittance or reflectance, or with a multifunctional sphere capable of both.
• Solar and Photopic Optical Measurements: Supports directional-hemispherical and directional-directional measurement modes. The solar absorptance is calculated as one minus the sum of the directional hemispherical reflectance and transmittance.

Applications

ASTM E1175-87(2022) is especially valuable in fields where understanding the optical performance of non-uniform materials is essential:

• Architectural and Building Materials: Evaluate solar reflectance and transmittance of energy-efficient windows, façade materials, and blinds to optimize daylighting and thermal performance.
• Renewable Energy: Characterize surfaces used in solar panels and collectors, where accurate measurement of reflectance and absorptance can directly impact energy conversion efficiency.
• Product Development and Quality Assurance: Useful for manufacturers of advanced composites, textiles, and polymers to validate product consistency and compliance with energy performance standards.
• Research and Development: Provides a reliable method for researchers and engineers developing new materials with complex structures or surface geometries.
• Regulatory Compliance and Certification: Supports conformity assessment with energy codes and promotes best practices for sustainable building design according to international guidelines.

Related Standards

For comprehensive evaluation and standardization, consider reference to these related ASTM standards:

• ASTM E772: Terminology of Solar Energy Conversion - Provides essential definitions used in solar energy measurements.
• ASTM E892: Tables for Terrestrial Solar Spectral Irradiance at Air Mass 1.5 for a 37° Tilted Surface - Relevant for simulating real-world solar conditions.
• ASTM E903: Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres - Focuses on conventional integrating sphere methods, suitable for homogeneous materials.

By incorporating ASTM E1175-87(2022) into testing protocols, organizations ensure high accuracy, repeatability, and relevance of optical property measurements for both homogeneous and heterogeneous materials, supporting innovation and regulatory compliance in solar energy and architectural applications.