[Bldg-sim] Window performance with frames

D. Charlie Curcija curcija at designbuildersoftware.com
Fri Jul 16 13:50:46 PDT 2010


Nick,

 

I haven’t used eQuest in a long time, so I am not sure how is that
windows/glazing list incorporated into the program.  If the list shows NFRC
U, SHGC and VT and internally eQuest uses DOE2 report file, then the answer
to your question is no, there is no 10-100% error.  If eQuest just applies
those fixed values without using DOE2 report, then yes, large errors are
associated with window treatment.

 

NFRC lists specific products for which rating is available.  They are not in
business of providing baselines.  I guess that is more appropriate for
software developers.  That is the reason that in our software tool we have
extensive list of products matching ASHRAE Fundamentals list of typical
windows, which would easily enable user to select 90.1 compliant window.

 

Window5 is WINDOW 5.2, so yes that is the same program.  Please note that
there is already WINDOW 6.2, which now models shading devices and other
diffuse layers, in addition to specular glass.

 

Charlie

 

From: Nick Caton [mailto:ncaton at smithboucher.com] 
Sent: Friday, July 16, 2010 1:27 PM
To: D. Charlie Curcija; Andy Hoover; Alex Krickx; Otto Schwieterman;
bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] Window performance with frames

 

Mr. Curcija and everyone:

 

If I may be so bold as to ask some “dumb” questions,

 

-          I’m an individual who regularly relies on the DOE2 Glass library
(a large excel file attached to any eQuest installation) to find window
constructions whose NFRC framed U-value, visible transmittance, and SHGC/SC
values best match those prescriptive values given for actual design models
and for 90.1 baseline models.  Am I to understand all of my past models have
a “10% to 100% error” with regard to the modeled behavior of the glazing?
Please explain!

-          It sounds like the use of Window5 is pretty popular, and this
ability to export a file which can be used by DOE2 has me intrigued – has
NFRC or any other body decided to make representative report files to match
90.1’s baseline envelope requirements to encourage this procedure for
comparative studies?

-          Is Window5 the same thing as WINDOW?

-          Furthering Otto’s original question, my reaction to a reviewer
requiring “VLT including the frame” would be to first roll my eyes and then
explain the frame has a VLT of zero, and is modeled distinctly from the
glazing which has a VLT of ##%
 am I misunderstanding the request there?

 

Thanks!

 

~Nick

 

cid:489575314 at 22072009-0ABB

 

NICK CATON, E.I.T.

PROJECT ENGINEER

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

Check out our new web-site @ www.smithboucher.com 

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of D. Charlie
Curcija
Sent: Friday, July 16, 2010 9:16 AM
To: 'Andy Hoover'; 'Alex Krickx'; 'Otto Schwieterman';
bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Window performance with frames

 

Important thing to remember with windows is that the real number is the one
that account for actual size and that takes into account angle dependent
properties of glazing.  In most cases, single performance indices at
standard conditions are used (i.e., U-factor, SHGC, and VT at normal
incidence and standard environmental conditions) in an energy model of a
building, which can produce errors anywhere from 10% to a 100%!!  The
correct procedure is to either specify correct configuration and size of the
product, with glazing specified  layer by layer (possible in EnergyPlus) or
use what is called DOE2 or EnergyPlus reports from WINDOW program (DOE2
report is used in DOE2 simulation program and E+ report is used in E+
simulation program).  This is the only way to fully account for changes in
size, angular properties of glazing and actual weather conditions.

 

NFRC (National Fenestration Rating Council) has started to provide DOE2 and
E+ report files in their new CMAST certification system, however number of
products available is still relatively small and is limited to commercial
projects.  EnergyPlus has also implemented in version 5.0 option to specify
standard numbers at standard conditions (like the ones available from
http://search.nfrc.org/search/searchDefault.aspx) and E+ uses then internal
algorithms to provide glazing angular information and correction for actual
conditions.  While it is best to model specific configurations for a window
in THERM and WINDOW program (THERM is required to model frames and edge of
glazing), this is not something that average user will be able to do, so
getting whole product information from the NFRC web site and using E+ option
to convert this data to something resembling real performance is still the
best and easiest way to get actual information.  For commercial products
http://cmast.nfrc.org provides full information that does not need any
simplifications or corrections.

 

Our energy simulation tools DesignBuilder and EFEN use EnergyPlus simulation
engine, with the full range of options mentioned above and also provide
hundreds of predefined fenestration products that can be matched to your
actual product.

 

D. Charlie Curcija 
DesignBuilder Software 
16 Bridge St. 
Millers Falls, MA 01349
  
Tel: (413) 256-4647 
Fax: (413) 256-4823 
cell: (413) 575-3487 
email:  <mailto:curcija at designbuildersoftware.com>
curcija at designbuildersoftware.com 
web:  <http://www.designbuildersoftware.com/>
http://www.designbuildersoftware.com 
  

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Andy Hoover
Sent: Friday, July 16, 2010 9:01 AM
To: 'Alex Krickx'; 'Otto Schwieterman'; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Window performance with frames

 

Hey all:

 

We do not know Alex at all but completely support his position that it is
the entire assembly/full frame in use that counts.   We are a building
envelope consultancy and deal principally in the built market and see this
issue all of the time where the performance of window, storefront and
curtain wall units is dramatically different than that ‘calculated’ or
provided.   As a matter of fact, it is the unfortunate norm.  At the end of
the day it is about actual in use performance and that performance versus
what was calculated.  I will stay away from installation difference in this
one J.

 

Anyway, we do agree with and have seen the truth to his assessment of frame
differences.  It is only the performance of the entire assembly, at every
level of a structure as a whole, that counts in the real world.  

 

Thanks and take care,

 

Andy 

 

Andy Hoover

Principal

The BEST Consultant, Inc.

Cell: 678-793-1159

Office: 678-200-7648

Fax: 678-827-0574

Email: andyhoover at thebestconsultant.com

Web: www.thebestconsultant.com

 

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From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Alex Krickx
Sent: Wednesday, July 14, 2010 4:57 PM
To: Otto Schwieterman; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Window performance with frames

 

Hi Otto,

 

Serious Materials provides full frame performance data here:
http://index.seriouswindows.com/document-library/Datasheets/. I have also
have some of our commercial packages modeled in curtainwall and storefront
framing systems that I can provide upon request.

 

Firstly let me say that Window5 is a great tool – I use it often and love
it. The only thing I would advise is that there can be a wide distribution
in frame U-factors. The default U-factor for a thermally broken aluminum
(TBA) frame in Window 5 is U-1.0. Using THERM and Window5 I’ve seen TBA
frame U-factors vary from as low as 0.8 to as high as 1.5. The resultant
full-frame U-factor using these 2 differing TBA frames (and the same glass
package) is: 0.29 (R-3.4) for the poorer performing frame, and 0.22 (R-4.5)
for the better frame.

 

I would say that putting either of those full frame u-factors in your energy
model will yield pretty different results. 

 

I think it’s really important that we, as simulators and modelers, look at
full-frame performance because this is the system that will be installed in
the building. Center-of-Glass data can be useful comparing two different
glass packages, but at the end of the day, it’s a framed system that will be
installed and a framed system that should be analyzed. My 2¢.

 

Regards,

Alex Krickx

 

 

Alex Krickx

Building Energy Specialist

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1250 Elko Dr, Sunnyvale, CA 94089

(t) 408.541.8124

 

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From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Otto
Schwieterman
Sent: Wednesday, July 14, 2010 1:10 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Window performance with frames

 

Does anyone know of a window manufacturer web site that has literature on
its windows including the frame? I am using Trace 700 for EA Credit 1 and
the reviewer asked for manufacturer data sheets for window performance
values (U-value, VLT and SHGC) including the frame. 

 

Your help is appreciated,

 

Otto

 

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