ASTM E1980 Solar Reflectance Index (SRI) Calculation Services
ASTM E1980 is a standard practice that outlines the calculation of the Solar Reflectance Index (SRI) of horizontal and low-sloped opaque surfaces. The practice is intended for surfaces with emissivity greater than 0.1.
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- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
Overview
ASTM E1980 is one of the most critical test methods to determine the solar reflectance properties of building materials and surfaces. Solar reflectance and thermal emittance significantly influence ambient air temperature at the surface and in the near-surface region. Surfaces with low solar reflectance absorb a large portion of the incoming solar energy. A portion of this absorbed energy is reflected into the sky, a portion is converted to the air (raising air temperatures), and a portion is transmitted into the earth and buildings. A surface’s steady-state temperature increases as its emissivity decreases under similar conditions. Low-emissivity surfaces heat up because they cannot radiate efficiently to the sky.
ASTM E1980 measures the combined effects of solar reflectance and thermal emittance, which together depict surface temperature and energy performance. The results help manufacturers efficiently test opaque surfaces to reduce heat buildup while operating at extreme temperatures.
Scope, Applications, and Benefits
Scope
Surface solar reflectance and thermal emittance are crucial factors affecting ambient air temperature at the surface and in the near-surface region. ASTM E1980 can be used to measure it. Surfaces with low solar reflectance absorb a large portion of incoming solar energy. Conversely, low-emissivity surfaces warm because they cannot radiate heat to their surroundings. The Solar Reflectance Index (SRI) is computed using thermal emittance and solar reflectance. Designers and manufacturers use these numbers to choose appropriate materials for energy-efficient products.
Applications
- Evaluation of roofing materials for residential, commercial, and industrial buildings.
- Assessment of cool roofs and reflective roof coatings.
- Selection of paving materials for walkways, parking lots, and urban infrastructure.
- Used in building energy modeling and thermal performance analysis.
- Applied in sustainable architecture and green building projects.
- Material comparison during product development and R&D.
Benefits
- Provides a standardized method for calculating the Solar Reflectance Index (SRI), ensuring consistent, comparable results.
- Helps in quantifying the heat retention of roofing and paving materials exposed to sunlight.
- Supports the design of energy-efficient buildings by enabling the selection of materials that reduce heat absorption.
- Assists in reducing cooling loads and energy consumption in buildings.
- Enables evaluation of thermal comfort on roofs and outdoor surfaces.
Testing Process
Input Property Measurement
Measure solar reflectance and thermal emittance of the test surface using relevant ASTM test methods
1Reference Surface Selection
Use standard black and standard white reference surfaces defined in the practice
2Surface Temperature Calculation
Calculate the steady-state surface temperature of the test material
3Result Interpretation
Express results as a dimensionless index indicating relative heat rejection capability
4Technical Specifications
| Parameter | Details |
|---|---|
| Standard | ASTM E1980 – Standard Practice for Calculating Solar Reflectance Index (SRI) of Horizontal and Low-Sloped Opaque Surfaces |
| Sample Types | Roofing materials, roof coatings, paving materials, tiles, membranes, and other opaque construction surfaces |
| Electrode Configuration | Not applicable (optical and thermal calculation-based method) |
| Measured Output | Solar Reflectance Index (SRI) |
| Environmental Influence | Calculated under standardized conditions of solar radiation, ambient temperature, sky temperature, and wind speed |
| Applicable Frequency | Not applicable (static thermal performance calculation |
Instrumentation Used
- Solar reflectometer (for solar reflectance measurement)
- Infrared emissometer (for thermal emittance measurement)
- Calibrated reference standards
- Surface temperature measurement device (thermocouples or infrared thermometer)
- Data acquisition and calculation software
Results and Deliverables
- Provides a reliable and standardized method for evaluating material performance under controlled environmental conditions
- Enables assessment of accelerated aging behavior of materials
- Supports long-term performance and durability prediction
- Simulates aging processes such as temperature exposure and oxidation effects
- Aids in informed material selection based on performance data
- Supports quality assurance in material and product development
- Helps in designing products with extended service life and durability
Frequently Asked Questions
ASTM E1980 is a standard practice for calculating the Solar Reflectance Index (SRI) of low-sloped and horizontal opaque surfaces.
Solar Reflectance Index (SRI) indicates the roof's ability to reject solar heat, and is the combined value of reflectivity and emittance.
Solar reflectance and thermal emissivity are measured at Certimac using a UV-VIS-NIR spectrophotometer and an emission meter in accordance with ASTM E 903 and ASTM C1371-15 and ASTM E1980-11.
To meet LEED requirements, a roofing material must have an SRI of 29 or higher for steep-slope (>2:12) roofing and a SRI value of 78 or higher for low-slope roofing.
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