Dear All,
One of our clients is pursuing compliance with requirements for pavings (SR at least 0.28, 3 years aged or initial SR of at least 0.33) and one paving manufacturer proposed the following measurements methodology for SR determination:
- Determination of the solar reflectance in accordance with ASTM E903-12. The solar reflectance is calculated using the selected ordinate method set out in Section 8.3.4. Ordinates are selected from the values of direct normal solar irradiance specified in Table X2.3 of ASTM E903-12 «50 Selected Ordinates for G173 Direct Normal Irradiance AM 1.5»
- Determination of the emissivity in accordance with ASTM C1371-15
Carrying out these two tests, a report is issued where the SRI according to ASTM E1980 – 11 will be shown. Based on the previous measurements made, the surface temperature and the SRI for each specimen will be determined.
Specimens required: a total of 3 specimens of minimum dimensions (100 x 100) mm. Regarding their shape it is essential that the specimen can be placed vertically and no material drops from it; the area to be measured shall be continuous (with no holes) and flat, so a big single stone will be best. If you have any 0/x grading, I propose to prepare a specimen using colourless polyester resin and grind the surface.
Is this methodology acceptable for determine the SR of pavings that can be contribute for nonroof measures eligible for SS C5 Heat Island Reduction Credit compliance?
Thanks in advance,
Martha Norbeck
PresidentC-Wise Design and Consulting
71 thumbs up
May 18, 2021 - 12:03 pm
Ricardo, I ran into a similar issue. The testing laboratory delivered a report basedon ASTM E1980 results. I wrote to request additional clarity. This is their response. I will note that the current online credit description no longer references any testing protocol and v4.1 has a completely different ANSI protocol. (Insert comments of irritation here.)
The ASTM C1549 does not supplant ASTM E903 method. However, per section 1.2 of the ASTM C1549, this technique is supported by comparison of reflectometer measurements with measurements obtained using Test Method E903.
Also, C1549 method provides a table showing the difference between the two methods (C1549 vs. E903). On average, for the seven tested materials, the C1549 test method yields solar reflectance results at air mass 1.5 that are 0.019 (1.9 %) greater than those obtained with Test Method E903.
In general, regardless of the different types of equipment used by these methods, the test method E903 measures solar reflectance over the wavelength range 250 to 2500 nm using integrating spheres. The C1549 uses the portable solar reflectometer which is calibrated using specimens of known solar reflectance to determine solar reflectance from measurements at four wavelengths in the solar spectrum: 380 nm, 500 nm, 650 nm, and 1220 nm.
Regarding your statement; “The SRI according to ASTM E1980 is based on two tests. 1) determination of Solar Reflectance in accordance with ASTM E903-12, and 2) Determination of the emissivity in accordance with ASTM C1371-15.” , E1980 provides approaches to calculate the SRI given solar reflectance value (which can be obtained using E903 or C1549) and thermal emissivity in accordance to C1371. With respect to the latter, since most nonmetallic opaque materials at temperatures encountered in the built environment have emittance values between 0.85 and 0.95 (based on 2005 ASHRAE Handbook Fundamentals), the average value of 0.9 is normally employed to calculate the SRI in general accordance with C1980.
Additional notes:
emily reese moody
Sustainability Director, Certifications & ComplianceJacobs
LEEDuser Expert
476 thumbs up
May 19, 2021 - 11:39 am
Ricardo, if your project needs to attempt a variation or needs specific feedback on something technical like a standard, it's safest to discuss it directly with LEED Coach or GBCI, as they will sometimes provide project-specific feedback that may become part of your documentation to be submitted.
Thanks to Martha for being able to provide such thorough insight!