Another useful source is Table 1 in this link, http://www1.eere.energy.gov/femp/pdfs/coolroofguide.pdf
Note E+ input is absorptance not reflectance and that Absorptance + Reflectance = 1.
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Jim Dirkes
Sent: Thursday, October 04, 2012 2:08 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: RE: [EnergyPlus_Support] SRI/Reflectivity study
Brent brings up an excellent point. You don’t want to model the roof’s performance for “day 1” of its life. ASHRAE is saying that you should degrade the performance to reflectance of .45 when the published value is .70. Section 5.5.3.1 (mentioned by the excerpt below) cites several ASTM standards that I’m unfamiliar with, but I think the idea is to make sure the product passes an independent performance test … in order to qualify for using the .45 reflectance.
This does not address how to model the performance of differing SRI values; if I learn anything on that topic, I’ll share it here.
“For exterior roofs other than roofs with ventilated attics, the roof surface may be modeled with a reflectance of 0.45 if the reflectance of the proposed design roof is greater than 0.70 and its emittance is greater than 0.75. The reflectance and emittance shall be tested in accordance with the Exception to Section 5.5.3.1. All other roof surfa
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