[BLDG-SIM] energy consumption of low-E glazing , why the cooling energy increases

[Llona, Joseph]

I ran into this once on  lab project in the northwest (mild climate).  Turned out the higher performance glazing was trapping the high internal heat gains. Higher cooling energy and lower heating energy.
 
Joe Llona, P.E. LEED® AP, CSBA | Senior Mechanical Engineer
Direct: 206.883.9318 | Main: 206.883.9300 | Fax: 206.883.9301
joseph.llona at tetratech.com

Tetra Tech | Infrastructure Group
1420 Fifth Avenue, Suite 600 | Seattle, Washington 98101 | www.tetratech.com

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________________________________

From: BLDG-SIM at gard.com on behalf of nicole chen
Sent: Mon 7/30/2007 1:03 AM
To: BLDG-SIM at gard.com
Cc: bldg-sim at gard.com
Subject: [BLDG-SIM] energy consumption of low-E glazing , why the cooling energy increases


What I did is define a new glass type with simplied method in detailed model. Then replace the old glass with the new defined one. Can this do? How to avoid the defauls percolate through the program? I check again and find that there was no wrong with the conduction heat and solar radiation through window .But the load due to occupancy /lighting/euqipment of Glass Type II is higher than Glass Type I . And the cooling energy of Glass type II is a little highter. It make me confused. Why the load due to  due to occupancy /lighting/euqipment  was different when Glass type changed. 
 
And I doubt if the problem has something to do with OA load .

 
On 7/29/07, Karen Walkerman <kwalkerman at gmail.com> wrote: 

	Hi nicole,
	
	I can't tell you why the heating energy of glass type II may be lower
	because of the better U-value.  With Shading Coefficients almost the 
	same, there should be little change in heat gain from solar radiation
	between the two types.
	
	What method did you use to enter your data?  You should be careful of
	defaults that can percolate through the program.  For example, the 
	window frame U-value may not be consistent, or the glass spacer-type
	may be different.
	
	Another good place to look for some feedback is the building and space
	peak loads summary.  Here, the solar gain (heat energy gained through 
	radiation) and simple conditioning (energy transfered through the
	glass-same as walls), are broken out.  The heating design case will
	not take solar radiation into account.
	
	Hope this helps.
	
	~karen~ 
	
	On 7/29/07, nicole chen <cloris.chen at gmail.com> wrote:
	> Dear all
	>
	> I have tried to compare the energy consumption between two different glass
	> types and got a curious result. The parameters of these two glasses are
	> listed below:
	>
	> 1) Coated U=2.5 SC=0.45
	>  2) low-e U=1.76 SC=0.44
	>
	> I thought the energy consumption of Glass Type II would be lower than that 
	> of Glass Type I . But the result is the cooling energy of Glass Type II is
	> higher than  that of Glass Type I , and the heating energy lower than that
	> of Glass Type I.
	>
	> I have no idea of this. And I checked LS-F/ SS-D / BEPS and found some 
	> points listed below
	>
	> 1) in LS-F annual sensible  cooling load of Glass Type II is lower than that
	> of Glass Type I , latent cooling load of Glass Type II is higher. The total
	> annual cooling load of Glass Type II is a little higher 
	>
	> 2) in SS-D monthly cooling energy of Glass Type II is  higher
	>
	> 3) dencity and schedule of occupancy /lighting /euqipment are the same in
	> the two models , but cooling load and heating load due to these indoor 
	> factors are different , why?
	>
	> 4) monthly schedule of occupancy /lighting /euqipment  is all the same
	> during the year, but cooling load and heating load due to these indoor
	> factors are different every month, why? 
	>
	>
	>
	> --
	> Yours
	>  Nicole Chen
	
	
	--
	Karen Walkerman
	Second Law Consulting
	802-238-0980
	kwalkerman at gmail.com
	




-- 
Yours
Nicole Chen 


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