Window NFRC ratings and airtightness
I’ve read about NFRC rating. Intuitively, infiltration seems like it should be one of the more important considerations- if the window is leaking air, the U/R value seems secondary.
我正在寻找列出了NFRC的Windows。然而，网站上的NFRC列表似乎并不包括许多窗户的渗透。您可以通过制造商和窗口类型导航到特定的窗口，从中选择产品行，然后将您带到“常规信息：和评级表”的页面。
一般信息包括用于空气泄漏的单元，但对于许多窗户，空气泄漏是空白的。在评级表中，有一个柱子用于U型因子，SHGC，VT和凝结电阻。如果我单击特定窗口的CPD＃链接，它会带上一个弹出窗口，其中包含一个用于空中渗透的框，但该框也是空白的。
它似乎是为了满足能源之星，窗户必须具有小于0.3.cfm / ft2的渗透。制造商的网站有一个页面，表示空气渗透为0.05（CFM / FT2的框架@ 1.57 PSF风压）。
At first glance 0.05 seems good, but since it does not appear on the NFRC site, I’m suspicious of the number. Is there any good reason a window from a national manufacturer would not have it’s air infiltration rating on the NFRC site? Is the psf of 1.57 appropriate? What psf is associated with the Energy Star requirement of 0.3 cfm/ft2 assume?
Replies
C.L.,
First, window manufacturers who voluntarily decide to test their windows according to NFRC labeling requirements must report U-factor, SHGC, and VT, but they aren't required to report air leakage. Air leakage testing is a voluntary element of this voluntary program. Window manufacturers negotiated for a certain amount of wiggle room -- making the reporting of air leakage optional -- when the NFRC program was established.
The适用于Windows的能源之星does include a maximum air leakage threshold -- namely ≤0.3 cfm/f2 for most windows. The Energy Star Window Specification does not specifically list the test pressure, but references test standards.
The most common way that window manufacturers comply with the Energy Star requirement for window air leakage is to comply with the NFRC test procedure. TheNFRC test procedure for window air leakagereferences ASTM E283, which requires testing at a pressure difference of 75 pascals (with the exterior of the window pressurized with respect to the interior).
If a window manufacturer is reporting an air leakage result without referencing ASTM E283 or NFRC, there is no way to know the pressure at which the window was tested. If the window was tested at a pressure difference of 5 pascals, it's relatively meaningless.
A test pressure of 1.57 psf (the test pressure reported by the manufacturer you mention) is equivalent to 75 pascals, and is therefore a meaningful test. If you doubt the manufacturer's report, ask a technical help representative to send you a copy of the third-party laboratory result. A reputable window manufacturer should comply with that request.
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Martin - thank you very much for the thorough response.
基于上述信息，是否正确结论：
1. Although NFRC does not require infiltration testing to be reported, Energy Star does require infiltration testing.
2.如果产品是能源之星认证，制造商必须提交渗透测试数据以证明渗透为<0.3 CFM / SF，并且其中一个可接受的测试程序要求在75帕斯卡的压力差的压差下进行测试等于1.57 psf
So my follow up question is regarding the infiltration numbers, assuming they were done per the Energy Star requirements. How big a difference does it make to use a window that reports it is only Energy Star compliant (assume just met <0.3 cfm/sf, or is 0.299 cfm/sf) vs a window that reports 0.2 cfm/sf. I know that is 0.1 cfm/sf difference, but is that negligible or a big deal? Energy Star only requires doors to meet <0.5 cfm/sf, and there are plenty of doors that still do not carry an Energy Star label...
C.L.,
Your two numbered points are correct statements.
没有简单的方法来描述高性能窗口的较低漏气速率。大多数具有能源之星窗户的房主都很开心，并且不要抱怨空气泄漏。
However, if your house is on a cliff facing the ocean in northern Maine, or if you are building a Passivhaus, you may want to invest in windows with a lower air leakage rate than a run-of-the-mill Energy Star window.
Calling the mfg for infiltration test data is hopeless. I get bounced around and nobody knows who has the answer, and they all want to know why I need the info...I don't get the impression they don't want to disclose the info, but rather that this is an unusual question, and they have 10's or 100's of people who work there, and I did not happen to get bounced to the 1 or 2 people in their technical department who understand the question, much less know how to provide the answer.
我发现以下数据埋在他们网站上的文件中。这是一个窗口，每个NFRC网站遇到能量明星，所以渗透必须是<0.3 / CFM / SF，但超出此，如果有人可以帮助我理解这一数据，这将是非常有帮助的。与能量星分钟相比，空气渗透看起来很好，并且每个马丁的注意事项似乎在适当的帕斯卡尔测试，但这些数字会在被动房屋上进行适当的窗口（我不建造ph，只是pgh，但只是pgh，但是试图了解幅度差异的顺序）？耐水性和设计压力数是什么意思？任何帮助极大地感激。
Performance
Meets or Exceeds AAMA/WDMA: Ratings R30-R50; Hallmark Certified
- Air Infiltration (cfm/ft2 of frame @ 1.57 psf wind pressure): 0.05
——水电阻:7.5 psf
- 设计压力：30-50 psf
C L.
I fell into the same chasm as you recently. That info you are looking for is non-existent on same company's websites, or proudly displayed on others. You will find that some windows with great U values can have horrid air infiltration numbers, or unacceptable water resistance numbers. If you start looking at sliding doors and these values, god help you. Some doors fail so badly I would be ashamed to be the seller. Some of those doors are incredibly expensive. Anyway, for the best explanation, I refer to this quote by the mighty window guru Oberon476:
"The DP rating of a window or door is based on laboratory pressure testing in pounds per square foot or psf.
Air, water, structural is a three part test that determines much about a window's overall performance. Air infiltration is the first phase, water penetration is next, and structural is the third part of the test.
Windows are tested for air infiltration simulating a 25mph wind or a 1.56PSF pressure load - air infiltration is treated separately from both water infiltration and structural and it is independent of the design pressure of the unit. Said again - the air infiltration rate in a window is not based on the design pressure rating of the unit.
Both water penetration and structural testing, on the other hand, are based on the window DP rating. Water infiltration is tested at 15% of the design pressure and structural is tested at 150% of DP rating.
What this means is that a window with a DP30 is tested for water infiltration at 4.5psf (15% of 30psf) while a window with a DP40 is tested at 6psf (15% of 40).
迪拜的一个窗口30 rating should be able to keep out rain when its driven by 42mph winds and a window with a DP40 should be able to keep out rain when driven by 49mph winds...so while water infiltration is DP related - and air infiltration is not - the nature of air and water infiltration is different.
The structural rating of a window is as much about the glass as it is about the frame and sash system. In order to get a higher DP rating the window manufacturer has to consider the thickness and possible heat-strengthening (or tempering) of the glass as well as the use of higher-end hardware and good quality sealants in the frame and sash system. But, interestingly, there is nothing in the structural rating that specifically requires that the unit be air-tight.
窗户可以像筛子一样泄漏空气，仍然达到优异的DP等级。同样，密封的窗户可以具有较低的DP额定值，但优异的空气渗透号。显然，还有许多单位具有出色的空气渗透数和令人满意的DP额定值（与结构强度和水浸润有关）。
Simply stated, the relationship between DP and windspeed is -- "the ratios of the design pressures in psf are the square of the ratios of the wind-speeds in mph".
迪拜的一个窗口30 is rated to a pressure level equivalent to a 110mph windspeed, but it is tested (for structural) at a pressure equivalent to 164mph.
迪拜的一个窗口40 is rated to a pressure level equivalent to a 127mph windspeed, but it is tested (for structural) at a pressure equivalent to 190mph.
If you are curious about calculating the numbers yourself, a while back (at the request of a specific window company as a matter of fact) I wrote a couple of simple formulas that will allow you to do so...
If wind-speed is known, then:
W/25 * 0.0624 * W = psf
Where W = wind-speed
或者，如果已知设计压力，那么：
SQRT(psf) * 20.01 = wind-speed"
Take note of what he says about wind speed and DP ratings--i.e. The DP30 window should be able to keep out wind driven rain at 42mph. I don't know about you, but where I live, that is nothing. We can easily get 60mph+ rains. A DP 50 rated window would withstand a 55mph wind driven rain. The specs you show at the end of you post are actually pretty good from what I have found. A DP50, with water infiltration tested to 7.5psf and that super low air infiltration would be an above average window. I compared some slider doors recently:
Sierra Pacific推拉门，4个面板，中间两个是滑块，外面2固定。DP15！水测试到3.13psf，因此预计35英里小的风力下雨漏水。它几乎没有通过.26 CFM / SF的空气渗透。
Jump up to the Cascadia Windows compression slider and we see air infiltration of .002 cfm/sf, and water penetration tested to 15psf(a 78mph rain). They rock!