[bldg-sim] Horizontal shading in EQUEST

Glenn Haynes glenn.haynes at rlw.com
Thu Jan 18 09:28:43 PST 2007


Rohini,

Is it possible that your system is allowed to autosize?  If so, you may
be reducing outside air when the fan CFM is reduced due to the cooling
load reduction.  This could explain the decrease in heating energy.

BTW, if you are designing a new building or sizing a new system, it is
OK to allow the system to autosize, and the surprising interactive
results of other changes may actually be valid.

But if you have a system (such as an existing system) that is not
actually going to change with some other change, you should not forget
to fix that system capacity (and, possibly other things) and run your
fixed baseline before you add the desired change and rerun the model.
With everything else fixed, all you will see are the effects of the
desired change.

Glenn

-----Original Message-----
From: bldg-sim at gard.com [mailto:bldg-sim at gard.com] On Behalf Of Rohini
Brahme
Sent: Thursday, January 18, 2007 10:40 AM
To: bldg-sim at gard.com
Subject: [bldg-sim] Horizontal shading in EQUEST

I have also seen similar results. If I remember correctly, I was
autosizing the system - and the sizing of the fan cfm is small with
shades - which seemed like the reason for lower heating. Also, reduction
in reheating is a likely cause - any report that just shows the
reheating energy? If you look at the LS-D report, you should find that
the heating has increased and the cooling has decreased.
 
Having said that, the shading results always tend to surprise me.
- Rohini
 
------------------------------------------------------------------------
------------------------------------------------------------------------
----
 
What do you mean by Horizontal Shading? Like fins (the device fin are
vertical, but cut down light horizontally) ??
 
I just ran a typical office (250,000 sf) in Fresno, CA in eQuest.  When
I put 2.5 ft fins on all the windows, I got a slight decrease in heating
as well (but not to your % level).
 
I traded the 2.5 ft fins with 2.5 overhangs. I got a 15% decrease in
cooling, and a 13% decrease in heating. This building is dominated by
VAV/reheat. What I can surmise is that when the cooling load decreased,
the need to reheat decreased as well. That the building is not skin
dominated for energy.
 
Anyone else have a clue?
 
John R. Aulbach, PE, CEM
Project Manager
Nexant, Inc.
100 North Barranca, Suite 820
West Covina, CA 91791 USA
Phone: 626-430-9054
Fax: 626-430-9060
email: jaulbach at nexant.com
 

________________________________

From: bldg-sim at gard.com [mailto:bldg-sim at gard.com] On Behalf Of Jaya
Mukhopadhyay
Sent: Wednesday, January 17, 2007 3:25 PM
To: bldg-sim at gard.com
Subject: [bldg-sim] Horizontal shading in EQUEST


I am examining several options for Horizontal shading for an office
building using EQUEST.
A synopsis of the answers is as follows:
	Total Annual Energy MBTU	 Space Cooling MBTU	 Space
Heating MBTU	
Unshaded Option	 8380	 2411.9	 308.1	
2.5 ft Horizontal shading on East West and South
 
7936.8	 2178.8	 284.2	
5 ft Horizontal shading on East West and South	  
7835
 
2158
 
269.7
 
The Questions:
1. Its very baffling to see the heating consumption go down too. I
wanted to see an increase in heating on implementing the shading
devices. How can I justify that decrease?
 
2. The building has a total area of 210273 sqft. with 15 ft deep
perimeter zones. The shading reduces the energy consumption by 5 to 6 %.
Is that acceptable?
 
Any help is greatly appreciated.
Thank you 
Jaya Mukhopadhyay

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