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

[Vikram Sami]

Just a theory, but do you have the daylighting option turned on? If so -
the visible transmittance (I am assuming Glass 2 is darker) will make a
difference. It will increase your lighting load, and in turn your
cooling load. 
 

Vikram Sami, LEED AP 
Direct Phone 404-253-1466 | Direct Fax 404-253-1366 

LORD, AECK & SARGENT ARCHITECTURE
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________________________________

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of nicole
chen
Sent: Monday, July 30, 2007 4:03 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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