Hi!
What's the best way to input a curtain wall system to allow for the repetitive vertical mullions? I can calculate system U factor based on the area of vision glass : overall area, but I don't see a way to input that directly...unless:
If the vertical mullions are already captured in the system U factor can I just ignore it and treat it like one huge picture window? So at FRAME-WIDTH I would just enter the width and properties of the perimeter frame and then at GLASS-CONDUCTANCE enter the corrected U-factor for the system?
I did search this in onebuilding.org, but didn't see it addressed.
Thanks!
MARK DARRALL, AIA, LEED AP BD+C, NCARB
Intriguing question. I did just a little looking around and found:
windows.lbl.gov/software/NFRC/NFRCSim6.3-2010-Manual.pdf.
*which is a link to the user manual for Window and Therm. Check it out. You
can create things, windows,etc., maybe even curtainwalls, using Window and
import them into eQUEST
Carol
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You can create curtainwall systems in Window and Therm - but I don't believe that eQUEST will import any of the frame conductance data. I think the best way to model curtainwall systems is to model the frame in THERM and WINDOW5, create a DOE2 report file - then import that file into eQUEST and manually edit the frame width and conductance to match what you calculated in WINDOW5/THERM.
Alex
Alex Krickx, LEED AP
Thank you! I'm working against a pretty hard deadline and don't really have time to learn two more software packages. I found some basis of design information for both the curtain wall and glazing - can I use manufacturer's design guide graphs and calculations? The graphs are "per AAMA 507." They also have charts for NFRC 100 overall U factors and NFRC 200 SHGC and VT.
I think the LEED reviewers just want to make sure we're accounting for the frames and not just getting COG.
Take care!
MARK DARRALL, AIA, LEED AP BD+C, NCARB
Mark, in the interest of time, you can accomplish what you would like to
through the Building Shell Wizard --
1. If you already have a Window 4/5 file from the manufacturer, attach it in
Wizard Screen 6 under Glass Category.
2. If you do not have this, right-click Glass Category and under Tutorials
and Reference, and navigate to DOE 2 Glass Library (xls). You will be able
to find something comparable to your glass type here. Select a Frame
Typeand Frame
Wd (in) which matches your curtain wall assembly.
3. Under Window Dimensions, Positions and Quantities, you can specify a Typ
Window Width (ft). Now comes the shortcut to avoid Custom Window/Door
Placement. If your fenestration design consists of an irregular, custom
pattern, count the number of vertical mullions you have, and divide the full
width of the curtain wall by that number. Enter that number into Typ Window
Width (ft). Though your curtain wall will not have the same appearance in
the 3D View, you are provided the same length of lineal feet of window
frame, which will result in the same overall assembly U factor.
I typically model curtain walls as a single window per exterior wall
surface, and increase the frame width to make the frame area equal to
the total non-glazed area of the window opening.
I select a glass type from the DOE-2 window library based on the closest
match of U-value and SHGC to the actual glazing selection.
Bill
Sounds like a good compromise. I'm concerned the corner zones would
take on the brunt of the frame/glass disparity, creating a large
contrast of skin loads on the perimeter.
Arpan Bakshi, LEED AP BD+C
I think Bill is saying that for each zone surface he would take this
approach, not that he is loading up the zones on the end with extra frame
and walls in the middle zones (if any) with none.
David
*
*
David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
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*
*From:* equest-users-bounces at lists.onebuilding.org [mailto:
equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Arpan Bakshi
*Sent:* Friday, May 06, 2011 8:03 AM
*To:* Bishop, Bill
*Cc:* equest-users
*Subject:* Re: [Equest-users] Modeling regular curtain wall systems
Sounds like a good compromise. I'm concerned the corner zones would take on
the brunt of the frame/glass disparity, creating a large contrast of skin
loads on the perimeter.
Arpan Bakshi, LEED AP BD+C
Good discussion. Thank you! Corner windows are a problem in general; you get more heat loss just by virtue of having a lot more conductive material concentrated there. We sometimes can pack those frames with insulation but the heat just flows through the walls of the extrusions anyway.
I'm going to write up my approach to my curtain wall issue for the reviewers and bounce it off you all here first for your feedback. I feel if I can make a good engineering judgment on it they (and you!) should be able to accept it.
MARK DARRALL, AIA, LEED AP BD+C, NCARB