Please help me understand NFRC window ratings
Please help me understand NFRC window ratings.
Are these numbers a fair comparison of window performance? Are all manufacturers rated under the same criteria? I read that some report center of window u value. Are Canadian windows rated under a different value? I understand the European windows use a different system.
I am considering WASCO windows. I haven’t seen any other manufacturer with NFRC ratings as good. I have no reason to mistrust WASCO. They have been very responsive and forthcoming.
But I struggle with how their u values can be this good. It’s Cardinal glass, warm edge spacer and low e coating. I don’t see a variable that would change the numbers this much. I’m in zone 6.
Thanks,
GBA has been a very valuable resource.
Jim
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Replies
Jim,
Q. "Are these numbers a fair comparison of window performance?"
A. Yes, as long as you are comparing an NFRC-rated window to another NRFC-rated window. Here is the caveat: you can't compare the U-factor on an NFRC label with a manufacturer's boast about a window's glass-only U-factor. (NRFC U-factor ratings include the window frame; a glass-only U-factor omits the frame.)
For an overview of these issues, see All About Glazing Options.
Q. "Are all manufacturers rated under the same criteria?"
A. No. NFRC ratings are voluntary. Some manufacturers participate in the NFRC rating program; others don't.
Q. "I read that some report center-of-window U-factor."
A. That's true -- some do, especially manufacturers from Canada and Europe. Let the buyer beware.
Q. "Are Canadian windows rated under a different value?"
A. Not really. Most Canadian manufacturers use the same test method to determine U-factor as U.S. manufacturers. But you need to know whether the manufacturer is talking about a center-or-glass U-factor or a whole-window U-factor.
Q. "I understand the European windows use a different system."
A. That's correct. The European system adds an additional wrinkle. You can't compare the center-of-glass U-factor measured in the U.S. with a center-of-glass U-factor measured in Europe. For more information on this wrinkle, see Presumptive European Superiority Syndrome.
Q. "I am considering WASCO windows. I haven't seen any other manufacturer with NFRC ratings as good. I have no reason to mistrust WASCO. They have been very responsive and forthcoming. But I struggle with how their U-factors can be this good."
A. If you want to double-check any claims by a manufacturer, visit the NFRC web site. Here is a web page showing Wasco ratings: NFRC Directory Search Results for Wasco.
For more information on Wasco windows, see this GBA article: New Green Building Products — February 2012.
-- Martin Holladay
Thanks Martin, everything I'm asking about revolves around the NFRC numbers from the web site. It shows WASCO windows with u values of .13 and .14. I haven't looked at all manufactures but the handful I checked don't come close to those numbers.
Jim,
I just checked 7 pages of Wasco window ratings on the NFRC web site, and I couldn't find any windows with a U-factor lower than 0.17.
Can you provide a link to the page that shows NFRC U-factors of 0.13 and 0.14?
-- Martin Holladay
This is interesting. I watched as a different supplier went through the pages and we didn't see these values. I just down loaded the info from NFRC and attached it showing these low (good) numbers.
Jim
Jim,
OK, I found the windows (WAS-K-8 series). Here is a link to one of the relevant NFRC pages:
NFRC Directory Search Results for Wasco WAS-K-8 series.
The listing looks legit.
Do any GBA readers have any familiarity with these windows?
-- Martin Holladay
From a quick look at Martin's link, I see some windows that are triple-pane low-e krypton filled, and U-0.13. Most US windows are argon filled. Another variable is distance between the panes--some of the better argon filled windows may use slightly bigger distance between the panes than other window manufacturers use. This can improve the U value in the center of glass (for modest thickness increases) and can also reduce the heat leakage through the spacers.
I'd be surprised if the investment in Krypton fill was worth the cost, but the improvements seem to be real and if the price does not deter you, it sounds like a good choice.
Thanks for the feedback.
The windows WASCO is quoting me are ;
Geneo 4700 with Triple Pane LoE 180 Glass is WAS-K-8-000088-00001 Argon u.15 SHGC .39VT.48
Geneo 4700 with Triple Pane LoE 366 Glass is WAS-K-8-000090-00002 Argon u.15 SHGC .15VT.34
Although they aren't cheap, they seem reasonable considering their ratings.
But I still don't see how they can appear to be so much more efficient than others and I don't get why the windows with great u values don't show up on the NFRC search pages but do on a download.
The advance search option was giving me trouble. I'll spend some more time with it or just use an Excel function to filter.
Thanks again- other thoughts- recommendations?
Jim
Jim,
The NFRC directory, and the search function on that site, are indeed (as you have found out) fussy and hard to use.
That said, if you use the link below:
http://search.nfrc.org/search/cpd/cpd_search_detail.aspx?cpdnum=WAS-K-8
... you can click all of the pages (see the page numbers at the bottom of the page) to see a huge variety of glazing options, all with different U-factors. So the low U-factors you are talking about do show up on the NFRC site.
-- Martin Holladay
Thanks again Martin, It is so much data that I find downloading it to a spreadsheet and sorting works great.
The WASCO windows are legit. They're a regular exhibitor at PHIUS conferences and are also listed in the PHIUS window directory. They use a high performance foam-filled PVC frame made by Rehau, in conjunction with high performance IGU's from Cardinal. Their lowest U-value units use 3 low-e coatings, including Cardinal's i89 coating on surface 6, facing into the room.
John,
Thanks very much for your comments. I appreciate hearing your endorsement.
As I wrote in my 2012 review, "Geneo profiles [offered by Wasco] have a lower U-factor (between 0.19 and 0.20) than typical vinyl profiles used by most U.S. window manufacturers. Wasco offers the high-performance Geneo profiles on its triple-glazed tilt/turn windows. Unlike most window manufacturers, Wasco Windows understands glazing options...."
-- Martin Holladay
Thanks John, sorry if it sounded like I was questioning WASCO. My problem was with the NFRC numbers. Some of this was operator error.
I have been dealing with WASCO and they couldn't have been more informative and helpful.