[Equest-users] building shade effect

Christian Kaltreider ckaltreider at sudassociates.com
Thu May 31 12:33:48 PDT 2012

One more thought since peak load from windows was mentioned earlier:  


In calculating peak cooling loads for sizing equipment (using Trane TRACE),
I have almost always found that the solar gains through windows were more
significant than conductance gains through windows...usually about 1.5 times
greater, sometimes much more.  This of course depends on the U-value, SHGC,
and orientation of the assemblies.  Unless a building is highly internal
load driven, I generally find that solar gain through windows is one of the
top three driving factors in peak cooling load (including lighting, plug
loads, ventilation, etc).  Adding effective building shades can often result
in appreciably smaller cooling equipment, potentially allowing the equipment
to operate under more favorable part-load conditions as well as saving money
up front.


With that said, peak design load and annual energy are two different
animals.  I agree that the overall percent energy savings on an annual basis
will be pretty low.  Just wanted to mention this peak load side effect.





From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Michael
Sent: Thursday, May 31, 2012 3:03 PM
To: 'Bobby Sy'; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] building shade effect


While I wouldn’t expect big savings from the shades, I think it might be a
bit higher than what you’re seeing because of the way its modelled. Using
proportional transmittance doesn’t account for how the shading varies with
sun angle. When the sun is high, less solar will get through. As Bill says,
I would model this as a building shade, actually putting each louver in. It
looks like the louvers are tubular, so you can probably approximate that
with a vertical shade and another one at 45°. 


While this sounds like a lot of work, if you use copy and paste in the inp
file it probably isn’t as bad as it sounds. Just need to change the z
coordinate once you’ve put the first ones in. You might consider doing it in
Excel, with a formula for the z, and then copying the results into the inp
file. That would be pretty quick.




Michael Wilson, P.Eng., Enerficiency Consulting

PO Box 1911 - 458 Abbs Rd., Gibsons, BC  V0N 1V0    |    604-886-9864    |


From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bobby Sy
Sent: May-30-12 7:19 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] building shade effect


Hello everyone!


I am working on a project, a high rise office building. The architect added
louvers as part of the design which I admire for sophistication. Attached is
a picture that shows the louvers outside for shading. But, when I did the
initial run, the effect of the louvers is only around 1% energy improvement
from the baseline.


Please let me know if there is a better way to do it in eQuest. What I did
was to measure the louver thickness and proportioned it to the glass area
that it covers. I put the fraction as "Transmittance:" in Building and Fixed
Shades properties. Doe 2 help says: 


Fraction of incident solar radiation that is transmitted by the shading
surface. The default value is 0.0, which means the surface is opaque. A
value greater than 0.0 represents a device that passes some solar radiation,
such as a tree, lattice, or fabric. Using SHADE-SCHEDULE allows seasonal
variation in transmittance. Daylighting calculation assumes TRANSMITTANCE =


The design team quite find it hard to believe that the louvers have very
minimal effect. I told them to consider the window to wall ratio (almost
60%) and that fact that they will be using a clear glass, even with these
louvers partial UV rays still pass through the gaps that spreads allover the
glass surface that adds to the heat load for air conditioning. Ive noticed
to some of my other projects in tropical countries, building shades don't
have much effect to energy efficiency. Did anyone encounter the same result
with building shades? 






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