[Equest-users] Diferents result with differents U-value in Weather 2A

Joe Huang yjhuang at whiteboxtechnologies.com
Wed May 22 14:14:35 PDT 2013


Dante,

If you are studying window performance, I would recommend that you use a more detailed 
physical model where you define the layer by layer properties of the glass as well as the 
thermal properties of the frame,  rather than the Simple Wndow Model (SWM) where you just 
enter the bulk properties of U and SHGC.  eQUEST contains a library of several hundred  
windows from which you can pick, don't know about the situation in EnergyPlus.

As far as the difference that you see between eQUEST and EnergyPlus for the same SWM 
inputs, I suspect they are using different angular solar properties.  Please remember that 
the SHGC is measured or calculated normal (perpendicular) to the solar radiation, but in 
actuality solar radiation is almost never normal to the window.  In a SWM, the angular 
solar properties are taken from available data for other windows.  In the original DOE-2 
SWM, the angular characteristics of a single-pane clear window are used, but I see your 
eQUEST input file has more SWM inputs, so eQUEST may have refined its SWM.  The SWM in 
EnergyPlus, on the other hand, only uses the U-value and SHGC, and guesses at the angular 
solar properties based on them.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
www.whiteboxtechnologies.com
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"


On 5/22/2013 10:48 AM, Dante Garcia wrote:
>
> Hello Joe,
>
> Thank you
>
> I just have change u-values in both cases.
>
> I am usinq this propierties: (NFRC Ufact=0.31, SHGC=0.25, VT=0.57)
>
> cid:image005.jpg at 01CE56EA.38A47100
>
> And using this in the other case:
>
> (NFRC Ufact=0.70, SHGC=0.25, VT=0.57)
>
> cid:image006.jpg at 01CE56EA.38A47100
>
> I did not have change anything more. And got that different (4%) when running each 
> model. I see that I can change more data in equest but in both models I maintained that 
> data iqual.
>
> I think that there is a problem in my model. Because is too much difference.
>
> I used Energy Plus just to compare. And I set just U-values, SHGC and VT.
>
> Regards,
>
> *Dante Garcia *
>
> *LEED Green Associate*
>
> *De:*equest-users-bounces at lists.onebuilding.org 
> [mailto:equest-users-bounces at lists.onebuilding.org] *En nombre de *Joe Huang
> *Enviado el:* miércoles, 22 de mayo de 2013 12:27 p.m.
> *Para:* equest-users at lists.onebuilding.org
> *Asunto:* Re: [Equest-users] Diferents result with differents U-value in Weather 2A
>
> Dante,
>
> How are you modeling the two types of windows in eQUEST and EnergyPlus?  If you're using 
> the Simple Window Model in both programs, the difference may be due to different 
> assumptions about the solar heat characteristics in their Simple Window Models.  Without 
> seeing the inputs, I can only guess, but it looks like with EnergyPlus the only change 
> is in the U-value, which as you say has a small effect due to the small delta Ts, but 
> with eQUEST, there may also be changes in the solar heat gain, which would also impact 
> the building energy use.
>
> Joe
>
> Joe Huang
> White Box Technologies, Inc.
> 346 Rheem Blvd., Suite 108D
> Moraga CA 94556
> yjhuang at whiteboxtechnologies.com <mailto:yjhuang at whiteboxtechnologies.com>
> http://weather.whiteboxtechnologies.com
> http://www.whiteboxtechnologies.com
> (o) (925)388-0265
> (c) (510)928-2683
> "building energy simulations at your fingertips"
>
> On 5/22/2013 9:33 AM, Dante Garcia wrote:
>
>     Hi all,
>
>     I am new using eQuest, I made a model in the DDWizard.
>
>     When I use a high performance glass U-value = 0.31, I got less efficiency than when
>     I modeled using an U-value =0.70, and the difference is about 4%, using enegyPlus,
>     that is the program that I have been using for a year show me differences in less
>     than 0.5% selecting diferents U-value because the range of temperatures is between
>     15-29 in a whole year in my country)
>
>     PDta: This is my first model using eQuest (I have another model that a friend gave
>     me, I change the wheater and model with both performance of glasses and I got same
>     result, So, I think that the problem is in my model)
>
>     Someone ran into with this problem?
>
>     Any help will be appreciate,
>
>     I have been using the sim file to figure out the problem but I could not find indoor
>     temperatures in each space.
>
>     *Dante Garcia *
>
>     *LEED Green Associate*
>
>     **
>
>
>
>
>     _______________________________________________
>
>     Equest-users mailing list
>
>     http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org
>
>     To unsubscribe from this mailing list send  a blank message toEQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG  <mailto:EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20130522/f1a95106/attachment-0002.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 2456 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20130522/f1a95106/attachment-0004.jpeg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 2345 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20130522/f1a95106/attachment-0005.jpeg>


More information about the Equest-users mailing list