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Solar Reflective Index

Danny Kelly | Posted in Green Products and Materials on

We are building a LEED for homes house and our client wants to use gravel for a driveway and some stained (grey) concrete for the sidewalks and patios. We need an SRI greater then 29. Have not found anyone that knows how to measure this – can anyone provide any help or suggestions?

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  1. GBA Editor
    Martin Holladay | | #1

    I haven't ever measured the SRI of a surface, but I have read about how it's done. You need a pyranometer. Here is more information:

    "A composite index called the solar reflectance index (SRI) is used by the U.S. Green Building Council and others to estimate how hot a surface will get when exposed to full sun. The temperature of a surface depends on the surface’s reflectance and emittance, as well as solar radiation. The Solar Reflectance Index (SRI) is used to determine the effect of the reflectance and emittance on the surface temperature, and varies from 100 for a standard white surface to zero for a standard black surface. ...

    "Ordinary portland cement concrete generally has an albedo or solar reflectance of approximately 0.35 to 0.45 although values can vary. Solar reflectance of the material increases as the surface reflectance characteristics of the concrete’s sand and cementitious materials increase. Surface finishing techniques also have an effect because smoother surfaces generally have a higher solar reflectance. For “white” portland cement, values are reported in the range of 0.7 to 0.8 (8). New asphalt concrete generally has a reflectance of approximately 0.05 and asphalt concrete five or more years old has a reflectance of approximately 0.10 to 0.15. ...

    "Albedo is most commonly measured using a solar reflectometer (ASTM C1549) or a pyranometer (ASTM E1918). ... Measuring solar reflectance using a pyranometer, ASTM E1918, “Standard Test Method for Measuring Solar Reflectance of Horizontal and Low-Sloped Surfaces in the Field,” is performed in the field on surfaces at least 13 ft (4m) in diameter. Measurements are done on a sunny day when the angle of the sun to the earth’s surface is greater than 45 degrees. For northern cities like Chicago, the best time to take measurements is April through August."

    Hope this helps. You can read more by clicking here.

  2. Danny Kelly | | #2

    Thanks Martin

  3. Jay Walsh | | #3

    ANSWER: LEED for Homes Credit SS 3.0 b) Reduce Local Heat Island
    Regarding the Solar Reflectance Index for the gravel drive.
    It appears this is irrelevant for Credit SS 3.0 b). There is one short sentence in the LEED Reference Guide, page 112 under “Approach and Implementation” that excludes this item. Here is how it reads, “Porous or permeable paving materials are encouraged and rewarded under SS 4.1 but are not acceptable strategies for this credit.”

    Hope this is of some help to you.

  4. Danny Kelly | | #4

    Thanks Jay - that pretty much answers my question.

  5. poplarnetwork | | #5

    As another resource, the Lawrence Berkley National Laboratory (LBNL) publishes a list of values for albedo, emissivity and SRI for common building materials. You can learn more about finding gravel values here:

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