[Equest-users] Roof reflectivity, emissivity and absorptance in equest

Aaron Powers caaronpowers at gmail.com
Fri Nov 8 18:10:49 PST 2013


Jeff,

For an opaque surface, you can just convert reflectance to absorptance by:
absorptance = 1 - reflectance.  This is the absorptance in the solar
spectrum.  The emittance (in IR spectrum) is a little more hidden.  In
detailed mode, if you select an exterior roof and look under the
"Daylighting - Shading - Other" you'll see the Outside Emissivity input.
 It sounds like you know where to input the absorptance, but just in case,
it is under the roof construction in detailed mode.  SRI is a calculated
value used to compare roof materials and so is not useful for energy
modeling software.

Aaron

Hi All,



ASHRAE refers to roof properties in terms of reflectance, emittance, and
SRI (Appendix G Table G3.1 5c). However, eQuest uses absorptance. I am
unable to find in the eQuest input areas (wizard and detailed) where there
is a means to input values other than absorptance. Is there a conversion
factor, or a place to input reflectance, and emittance or SRI that I am
unable to find?



Many thanks for your comments.



Best regards -



*Jeff Ross-Bain, PE, *LEED AP BD+C, BEMP
Principal

404-220-8940 Office

404-220-8955 Direct

*www.rbgb.com <http://www.rbgb.com/>*

Build Green. Save Time
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