[Equest-users] Roof Reflectiveness / Absorbency for cool roof

[Bishop, Bill]

Rob,
 
When I model cool roofs using ASHRAE Standard 90.1 Appendix G, I change
the absorptance of the roof construction to 0.55, per the
reflectance=0.45 allowance in Table G3.1. Energy savings may be modest,
or even negative, depending on several factors, including climate, roof
U-value, and electric-vs.-gas/heating energy rates. There are good
discussions in the archives regarding the nuances of cool/white roofs.
 
Regards,
Bill
 
William Bishop, PE, BEMP, LEED(r) AP | Pathfinder Engineers & Architects
LLP
Mechanical Engineer
 
 134 South Fitzhugh Street                 Rochester, NY 14608
T: (585) 325-6004 Ext. 114            F: (585) 325-6005
wbishop at pathfinder-ea.com           www.pathfinder-ea.com
<http://www.pathfinder-ea.com/> 
P   Sustainability - the forest AND the trees. P 
________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Rob
Hudson
Sent: Monday, December 06, 2010 1:58 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Roof Reflectiveness / Absorbency for cool roof
 
i am trying to model a cool roof by changing the absorbency from 0.7 to
0.55.  it is the right approach? i am getting an increase in energy
costs, which goes against logic.

-- 
Rob Hudson
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