[Bldg-sim] Window performance with frames
Alex Krickx
akrickx at seriousmaterials.com
Tue Jul 20 10:22:02 PDT 2010
Hi Mark,
I agree with the point you make, but I want to expand the conversation a bit. Specifically, I aim to discuss the difference between how to use NFRC values and how to input values into energy modeling software.
The NFRC value should be accurate for a window of the NFRC standard size. So a standard sized 1200mm x 1500mm fixed window will have a certain U-factor, SHGC and VT as part of its NFRC rating. But a different size will certainly have different performance values. I think NFRC is very useful in comparing Window A to Window B in a standard size, but you are right: once you've selected Window A we need to make sure that we have the right performance parameters for that sized window.
I've been working on some projects that are aiming to be Passive House certified in which case they DO need to know how performance varies with size. We've worked out some formulas to calculate the full frame performance (only for U-factor at this point) on a range of our products. It's tricky because you need to know the U-factor of each component (edge of glass against each part of the frame, each part of the frame, and COG) as well as the areas of each of those components which of course vary with different sized windows.
I'm not sure what other manufacturers are doing to be able to provide this, but we have some of our product lines in a format that we can provide an NFRC-grade value for a non-NFRC sized window.
If you want to see the calculations, you can follow this link: http://index.seriouswindows.com/passive-house.html and click "Download SeriousWindows for Passive House" at the bottom of the page or click here: http://index.seriouswindows.com/document-library/func-startdown/90/.
The document describes how the window is broken into different sections and includes all the necessary info needed to calculate full frame performance.
The last thing I'd like to add: It is probably simpler to upload WINDOW5 data (I know eQUEST can import COG spectral data), specify your window size in the modeling software and specify your frame U-factor. Your software should take all that data and calculate what the full-frame data is pretty accurately.
If anyone has any questions about this, feel free to contact me: generating these formulas took quite a bit of time and I'd be happy to share my learning.
Regards,
Alex Krickx
Alex Krickx
Building Energy Specialist
[cid:image001.jpg at 01CB27F2.96E06B90]
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 mark dewsbury
Sent: Monday, July 19, 2010 4:45 PM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Window performance with frames
Dear All,
Are we talking about the assessment for simple regulatory approval or are we talking about what a window really is. We have found dramatic variations between NFRC values and what actually goes into a building. I will not go into differences in measured infiltration rates as that is too random but the window framing factor is fairly parametric.
The NFRC tables work on a sample window size (lest say 900mm x 1200mm). This is quite a small window when compared to most installations but;
- For windows smaller than the sample size the frame to galls factor is much higher,
- Conversely for large format windows commonly used in residential & commercial projects the framing factor is much less. In some test cases we have calculated framing factors changing from 18% to 8% or even less.
Depending on Glass system and framing system this can create some interesting changes to thermal simulation results. One of my colleagues will hopefully publish something on this late 2010 or early 2011.
Mark Dewsbury
Centre for Sustainable Architecture with Wood
School of Architecture
University of Tasmania
Locked Bag 1324
Launceston 7250
ph: 03 6324 4089
mob: 0417 290 807
fax: 03 6324 4088
e: mark.dewsbury at utas.edu.au<mailto:mark.dewsbury at utas.edu.au>
________________________________
From: Alex Krickx [mailto:akrickx at seriousmaterials.com]
Sent: Saturday, 17 July 2010 5:05 AM
To: Nick Caton; D. Charlie Curcija; Andy Hoover; Otto Schwieterman; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Window performance with frames
Hi Nick,
I think I know the answer to some of your questions, for some others I'm happy to share my thoughts, and for the remainder I have no clue.
I have always assumed that for the DOE-2 Glass Library that those files have Window5 report files behind them - i.e. they're not just single values for U, SHGC and VT. I could be mistaken though.
Skipping number 2...
I believe that Window5 is the same thing as WINDOW (technically, I think it is called WINDOW5 and there is/soon will be WINDOW6).
Lastly - I've looked into some detail at how full frame U-factors are calculated and how they vary by size. So as a brief tangent, I thought I would look at whether SHGC varies by size too. I found that if a window had, say 0.5 SHGC COG and the window was 90% glass, 10% frame (by area) the resulting full frame SHGC was GREATER than (90%)*(0.5 SHGC). This means to me that the frame has some non-zero SHGC contribution. Granted, it was small (if I remember correctly on the order of 0.1) but still - non-zero!!! In my head I assumed that the frame would reflect additional heat through the window into the space - that may not be correct, but it made sense with my results. I haven't looked at VT that closely but I would assume the same is true - that the frame adds some small VT to the whole unit.
Regards,
Alex Krickx
Alex Krickx
Building Energy Specialist
[cid:image001.jpg at 01CB27F2.96E06B90]
1250 Elko Dr, Sunnyvale, CA 94089
(t) 408.541.8124
Warning: The information contained in this e-mail may be privileged attorney-client communications or attorney work product and/or proprietary and confidential. If the reader of this message is not the intended recipient then you have received it in error and any review, distribution or copying of this message is prohibited and you are to notify us immediately by reply e-mail and delete the original message immediately.
From: Nick Caton [mailto:ncaton at smithboucher.com]
Sent: Friday, July 16, 2010 10:27 AM
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
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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: curcija at designbuildersoftware.com<mailto: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 :).
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
[cid:image001.jpg at 01CB27F2.96E06B90]
1250 Elko Dr, Sunnyvale, CA 94089
(t) 408.541.8124
Warning: The information contained in this e-mail may be privileged attorney-client communications or attorney work product and/or proprietary and confidential. If the reader of this message is not the intended recipient then you have received it in error and any review, distribution or copying of this message is prohibited and you are to notify us immediately by reply e-mail and delete the original message immediately.
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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