[BLDG-SIM] Simplied windows and glass libraries

Timothy Moore tcm at berkeley.edu
Sun Apr 29 22:25:22 PDT 2007


A further clarification regarding modeling of whole-window U-Factor in
eQuest:
A closer look (confirmed by DOE-2 and Window5 documentation) reveals that
eQuest/DOE-2 does not reference the frame information in the DOE-2 report
generated by LBL Window5. In fact, the center-of-glass and "overall"
U-values indicated in the DOE-2 report from Window5 are the same (both are
COG values). 
DOE-2 calculates the overall U-Value as part of the hourly simulation based
on the frame width, conductance, and spacer type specified in eQuest.
Therefore, while you should still use the DOE-2 report from Window5 to
provide eQuest with the optical data for appropriate calculation of SHGC per
angle of incidence, you will still need to enter the frame width, U-value,
and edge spacer type in eQuest---assuming you’ve modeled the actual
dimensions of the fenestration. If you’ve lumped windows together into long
strips on each façade and want the overall U-value to be at least reasonably
accurate, you’ll need to add frame width for each window so that the
glass-to-frame area will be representative of the actual design.
Timothy

  _____  

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Robin
Mitchell
Sent: Wednesday, April 25, 2007 8:45 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Simplied windows and glass libraries


A point of clarification about WINDOW 5 and DOE2 files -- it is not possible
to use THERM files for export to the DOE2 file that WINDOW 5 makes. So the
method below, using the generic frame choices that come with WINDOW 5, is
probably the most straightforward way to create the window for DOE2.
 
Robin Mitchell
Windows & Daylighting Group
Lawrence Berkeley National Laboratory
 
 

  _____  

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Timothy
Moore
Sent: Wednesday, April 25, 2007 5:07 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Simplied windows and glass libraries


Kevin,
 
There is a method using LBL Window program that get the U-Factor for the
actual frame into the DOE-2 report without requiring you to get the
frame/mullion details and then model this in Therm:
 
First, based on selection of the actual glass from the international glazing
database, do the center-of glass calculation for the glazing unit within
that part of Window5. Then use the U-Factor charts for the frame/mullion
system(s) you plan to use or are considering (provided by most supplies of
curtain wall systems, etc.) to determine what the glazing system U-factor
should be for the appropriate ratio of glazed area to total area including
frame. Then return to Window5 and match the system U-Factor from this chart
by copying and modifying properties for the closest available frame
type/material in the Window5 frame library, checking the Total Window
Results when combined with your glazing unit. When, given the same
glass-to-frame area ratio, this result matches the one from the system
U-Factor chart for the frame/mullion system, you can then create the DOE-2
report from Window5 that you will reference in eQuest. Thus you will have
the angular optical data for the correct SHGC at each angle of incidence and
also an appropriate system U-Factor without having to actually model the
frame. This is particularly valuable if you are weighing a range of frame
systems with various insulating properties that also force or enable
different glazing units (i.e., they have a different maximum glazing pocket)
and you want to see the difference in the whole-building model.
 
Cheers,
Timothy
**********************************************
Timothy Moore
Integrated Sustainable Design Consultant 
LEED AP
Whole Systems Design
910 Indian Rock Ave.
Berkeley, CA 94707
Ph: (510) 525-4809
Fx: (413) 480-7252
Mobile: (303) 324-1044
 <mailto:tmoore at whole-systems-design.com> tmoore at whole-systems-design.com
 

  _____  

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of D. Charlie
Curcija
Sent: Wednesday, April 25, 2007 6:22 AM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Simplied windows and glass libraries


Kevin,
 
The best way to accurately model windows is with WINDOW and THERM software
(windows.lbl.gov).  These tools are also used for NFRC (National
Fenestration Rating Council) certifications.  However, you will need all of
the details of frame and glazing design to be able to utilize these tools.
WINDOW program is used to model glazing system and THERM program is used to
model frame and edge of glass sections.  The whole product is then assembled
again in WINDOW program, so WINDOW has dual role.  While WINDOW program is
easy to learn and can be accomplished in half a day, THERM program requires
2-3 days of training for novice users.  Several companies offer training and
our company (www.designbuildersoftware.com) is one of them.  WINDOW program
creates DOE2 report file, which can be used with DOE 2.2 to assign windows.
That provides the most accurate way to model windows energy performance in a
building.
 
If you don't have all of the details and wish to get estimated performance,
you can use one of the predefined windows in DOE 2.2, closest to what you
have.  You should not use simplified way (i.e., by assigning simple
U-factor, SHGC and VT as single number), because that produces gross errors.
EnergyPlus program, which is newer generation energy simulation engine from
DOE does not even have an option to specify windows and doors that way.  You
have to have WINDOW EnergyPlus report file (equivalent to DOE2 report file)
or use one of predefined windows in EnergyPlus.  Our tool DesignBuilder uses
EnergyPlus simulation engine, so you can try it out.
 
If you have further questions, you can contact us directly.
 
Regards,
Charlie Curcija
 

  _____  

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Kevin J.
Kyte
Sent: Tuesday, April 24, 2007 11:05 AM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Simplied windows and glass libraries


Can anyone offer advice on the most accurate route to model window
performance?
There are discrepancies between modeling glazing from doe library and then
modeling those values in simplified mode.
Is this steady state vs. transient heat transfer?  I am not familiar and I
could use a lesson in thermo.
Is this discussed in the Engineer’s Manual?  How about if I used Window5?
Will I be able to import Window files into Doe2.2?
 
 
 
I would be grateful of any assistance.
 
Kevin
 
 
 
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