[Equest-users] Exterior Color (Absorp.)

Joe Huang yjhuang at whiteboxtechnologies.com
Tue Sep 23 14:49:59 PDT 2014

This question has surfaced before on the bulletin boards, although more for window SHGC 
rather than roof absorptance.  If you're seeing something that's counter-intuitive, e.g., 
heating going up with increased absorptance, you should check to see whether the HVAC 
system size has changed.  What can happen is that the HVAC size will increase due to the 
higher cooling loads, so that during the heating season it will be lower on the part-load 
curve and result in increased heating energy use.


Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

On 9/23/2014 2:02 PM, Jones, Christopher wrote:
> When the absorptance is decreased, one would expect the heating load to increase and the 
> cooling load to decrease.  The overall energy difference would depend on which 
> increased/decreased more.
> *Christopher Jones**,***P.Eng./
> /Tel: 416.644.4226 • Toll Free: 1.888.425.7255 x 527
> *From:*Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On Behalf Of 
> *behnam jowkar
> *Sent:* Tuesday, September 23, 2014 3:57 PM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] Exterior Color (Absorp.)
> Hi All,
> When I reduce the roofing material absorptance value in my model, under construction 
> properties, my energy consumption increases instead of decreasing, which suggests that 
> this input is actually reflectance and not absorptance. has anyone experience something 
> similar or am I missing something here? Any input is much appreciated.
> Thanks,
> Behnam
> -- 
> Behnam Jowkar, MASc, BEng, LEED AP BD+C
> Mechanical Engineer In Training
> p: 416-716-5758
> e: behnamjowkar at gmail.com <mailto:behnamjowkar at gmail.com>
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