RE: [EnergyPlus_Support] Re: U value input

["Griffith, Brent" <brent_griffith@xxxxxxxx>]

I don't quite follow you, I ran your files and they seem to be reporting
similarly.  If you are looking at the Envelope Summary in the html
report, there does seem to be a problem with reporting of "U Factor with
Film".  

 

But in general, the best approach is to use the E+ report for U-values
without the film coefficients and then apply the film coefficients
yourself so that they agree with what the Standard is expecting.
Internally E+ doesn't use crude combined convection/radiation film
coefficients so reporting with the film coefficients is somewhat
arbitrary.  E+ is neutral with respect to specific Standards and it may
be that there are different film coefficients that need to be used
depending on the Standard.  

 

It is important to understand that film coefficients, and hence U-values
with film coefficients, depend on orientation (vertical, horizontal heat
flow up, horizontal heat flow down, etc) and are not uniquely defined
for just constructions.  So the reporting of these is by surface, not by
construction.  To get a report in eio file with film coefficients you
would need to add a "Report, surfaces, details;" input object to the idf
file.  See page 23 (or 29 absolute) in OutputDetailsAndExamples.pdf for
more information.

 

________________________________

From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of eric_zhou1223
Sent: Tuesday, January 22, 2008 10:55 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: U value input

 

Thanks a lot, Brent. I used the tool to output two files, the only 
difference between them being location and perhaps system type. Yet 
one of them can report "U-Factor with Film " and "U-Factor no Film", 
another can only report "U-Factor no Film". Would you please give 
me hint on this? Thanks again. I uploaded two files package named "U 
factor".

Eric

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx
<mailto:EnergyPlus_Support%40yahoogroups.com> , "Griffith, Brent" 
<brent_griffith@...> wrote:
>
> Not directly. E+ uses layer-by-layer descriptions and targeting a
> specific U-value often requires iteration. Tune the material 
properties
> of an insulation layer inside the construction. Be careful about 
the
> surface film coefficients when setting targets... (E+ can report 
them
> with or without, but Standards aren't always so clear). If the 
Standard
> is 90.1, you could try constructions out of an input file from the
> EnergyPlus Example File Generator. 
> 
> 
> 
> ________________________________
> 
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
<mailto:EnergyPlus_Support%40yahoogroups.com> 
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx
<mailto:EnergyPlus_Support%40yahoogroups.com> ] On Behalf Of 
eric_zhou1223
> Sent: Thursday, January 17, 2008 12:27 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
<mailto:EnergyPlus_Support%40yahoogroups.com> 
> Subject: [EnergyPlus_Support] U value input
> 
> 
> 
> Hi all,
> 
> Is there a simple way to define an U value for a wall,which is 
made of 
> several layers, like in eQuest? Given that I need to set the wall 
U-
> value to a standard value.
> 
> Eric
> 
> 
> 
> 
> 
> [Non-text portions of this message have been removed]
>

 



[Non-text portions of this message have been removed]



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