wow, never saw such a debate over Pella's designer series. Do I consider it a true triple, no, but I did get numbers for them at one time due to the blinds feature. The third pane of glass does help values some, but not as much as one would think. However they still have the nudge on the dual pane options, and gives you blind flexibility. This may not be important to many, but to us, with little dogs that love seeing out the window and ripping up blinds....this was something to consider.
My last house we remodeled I put in Pella windows, and had 0 issues with them. I have spec'd them in several projects, and have had 0 issues with them. It seems many of the leaking and rotting issues stems from bad installation, which can kill any clad window.

I think US companies are not seeing people going oversees to purchase windows. Infact I bet the % of people doing that is incredibly tiny. However I do think they see the market as energy standards are slowly increasing, and US companies want the edge for your typical US consumer. Pella has a newer high quality vinyl window with some pretty impressive numbers and glass options. It has triple seals and u values below .20. If I were a vinly fan and liked their color options, I would probably be putting these in my home due to it being a local Iowa company I would support with really good performance for a US company.

However I am going with Kolbe windows due to the triple pane glass packages I can get a long with all of the other options they come with we like, such as exterior colors, wood interiors, etc. My bid came in less than the Designers with u values in the low .20s and SHGC around .40 and up, depending on the elevation. One of my fixed windows u= .17 and SHGC is .49. Not bad for an alum clad wood framed US triple pane window....

Lbear-

So we can conclude that your use of the term "pure scientific definition" is not supported by any technical paper in a referred scientific journal. You may use any personal definition that you like, but do not be critical of others that choose to use a different definition.

Window performance values from European tests are not directly comparable with results from NFRC tests (For example, see http://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/do-europeans-make-better-windows-we-do). You like the European test protocol, but that is your personal opinion. There are some potential advantages for the NFRC higher differential temperature:
(1) For sizing heating systems, the choice of 0 F is probably a better choice for outside temperatures than 32 F for much of the northern U.S.
(2) The precision of the test results using a higher differential temperature is likely better than the precision of test results for a lower differential temperature. As zero differential temperature is approached, the uncertainty goes to infinity.

The Europeans typically give window performance values for center-of-glass only results, and most of us do not to compare those with NFRC results for complete windows. If you want to compare with European values, I suggest that you use the Cardinal Glass catalog that also has center-of-glass values. Center-of-glass U-values are on the order of 30% lower than whole window U-values (see same greenbuildingadvisor reference as above, especially the discussion following the article). That difference will explain much but not all of the European advantage that you always see.

Boy this has become funny awfully quick.

Scientific evidence?  Really, Lee?

Either 3 panes of glass are insulated, or they aren't, bottom line.

Posted By Lee Dodge on 07 Nov 2012 10:51 AM
Lbear-

So we can conclude that your use of the term "pure scientific definition" is not supported by any technical paper in a referred scientific journal. You may use any personal definition that you like, but do not be critical of others that choose to use a different definition.

Window performance values from European tests are not directly comparable with results from NFRC tests (For example, see http://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/do-europeans-make-better-windows-we-do). You like the European test protocol, but that is your personal opinion. There are some potential advantages for the NFRC higher differential temperature:
(1) For sizing heating systems, the choice of 0 F is probably a better choice for outside temperatures than 32 F for much of the northern U.S.
(2) The precision of the test results using a higher differential temperature is likely better than the precision of test results for a lower differential temperature. As zero differential temperature is approached, the uncertainty goes to infinity.

The Europeans typically give window performance values for center-of-glass only results, and most of us do not to compare those with NFRC results for complete windows. If you want to compare with European values, I suggest that you use the Cardinal Glass catalog that also has center-of-glass values. Center-of-glass U-values are on the order of 30% lower than whole window U-values (see same greenbuildingadvisor reference as above, especially the discussion following the article). That difference will explain much but not all of the European advantage that you always see.

There is some truth in what you say here, and some not.

Indeed the Euro testing methods are slightly different than U.S., and it makes apples for apples comparisons somewhat wonky.

Unilux has undergone "official" NFRC testing, for example, and I would put stock in that.

.16 u

Posted By michaeld on 07 Nov 2012 12:03 PM
There is some truth in what you say here, and some not.

Indeed the Euro testing methods are slightly different than U.S., and it makes apples for apples comparisons somewhat wonky.

Unilux has undergone "official" NFRC testing, for example, and I would put stock in that.

.16 u

Yes, that Unilux window has an excellent NFRC whole window U-value of 0.16 Btu/(hr-ft^2-F), and a low solar heat gain coefficient of 0.31 (http://search.nfrc.org/search/cpd/cpd_search_detail.aspx?cpdnum=UNL-K-6). Those window specs would be useful if you live in the many parts of Germany where the sun does not often shine between October through March. The low SHGC would make them undesirable for low-energy-consumption, heating-dominated housing in the central and northern U.S. and all of Canada unless the southern exposure for the house was already blocked, or there was some other reason to not make use of passive solar gain.

Is that the brand that you represent? Are the costs about $100/sq.ft.? Do they not have a higher solar gain window for the North American market with NFRC ratings? What is the European rating for this same low SHGC window with the NFRC rating of U-0.16?

I notice in http://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/looking-through-windows-part-5 a Unilux window that is rated (presumably European center-of-glass) at U-factor = 0.088 Btu/(hr-ft^2-F) and a SHGC of 0.5. That is possibly the same or at least a similar window, and shows that the European rating system certainly results in much better performance numbers, almost a factor of two lower U-value with a 61% higher SHGC!!! No wonder some thread participants are fascinated with European windows.

Posted By michaeld on 07 Nov 2012 11:57 AM
Boy this has become funny awfully quick.

Scientific evidence?  Really, Lee?

Either 3 panes of glass are insulated, or they aren't, bottom line.

When I get a chance, this can be discussed further. In the meantime, the principal heat transfer in a window occurs though convective and radiative heat tranfer between the panes of glass, with a smaller portion occuring in the frame and the heat transfer between the glass and the frame.

First ignore the radiative heat transfer (since it is outside the area of discussion) and focus on the convective heat transfer. As shown in the Appendix at: http://www.residentialenergylaboratory.com/r_value_cellular_shades.html each air layer between each glass pane adds a layer of insulation between inside and outside, with the glass panes themselves having inconsequential temperature drops. Thus, having two air layers between three panes of glass provides more insulation than having a single air layer between two panes of glass. In both cases, the air layers on the inside and outside of the windows add additional insulation. The insulation between the glass and the frame and between the panes are secondary in the overall heat transfer process. In the case of the Pella Designer Series, there in an insulating seal between the IGU and the 3rd pane.

I did not suggest that I was looking for "scientific evidence." Lbear said that "By the pure scientific definition of a true triple pane..." Since he introduced "pure science" into the discussion, I asked him for a reference to the scientific journal that he was quoting from, not any scientific evidence as you suggest.

Posted By Lee Dodge on 07 Nov 2012 10:51 AM
Lbear-

So we can conclude that your use of the term "pure scientific definition" is not supported by any technical paper in a referred scientific journal. You may use any personal definition that you like, but do not be critical of others that choose to use a different definition.

We will have to agree to disagree about what makes and does not make a triple pane window. I assume you would agree that a double pane window is two sealed panes with a sealed spacer? A single pane window with an operable unsealed storm window/blind storage space would not qualify as a double pane window. In regards to the triple pane, it is NOT my personal definition, it is the European definition; three sealed panes with two sealed spacers. Just like a double pane is two sealed panes with one sealed spacer.

I would also like to add that I called Pella and asked them about this series of window and even the tech operator stated that it is referred to as a "triple pane" window but they prefer to view it as a double pane window with an operable third pane. They agreed that the third pane of glass is more of a storm pane. Even Pella agrees with the European definition but US marketing allows them to sell it as a "triple pane" window and the FTC will not stop them because there are no standards when it comes to the definition here in the USA. We will have to agree to disagree but I am confident that the FTC and DOE will eventually make the European definition the official designation of what does and does not constitute a triple pane window. When that happens that particular Pella series will no longer be allowed to be called triple pane. Most likely it will be designated as a double pane window with an operable storm/blind storage pane.

I rest my case. Now onto to the other topic...

Posted By Lee Dodge on 07 Nov 2012 10:51 AM
Lbear-

Window performance values from European tests are not directly comparable with results from NFRC tests (For example, see http://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/do-europeans-make-better-windows-we-do). You like the European test protocol, but that is your personal opinion. There are some potential advantages for the NFRC higher differential temperature:
(1) For sizing heating systems, the choice of 0 F is probably a better choice for outside temperatures than 32 F for much of the northern U.S.
(2) The precision of the test results using a higher differential temperature is likely better than the precision of test results for a lower differential temperature. As zero differential temperature is approached, the uncertainty goes to infinity.

The Europeans typically give window performance values for center-of-glass only results, and most of us do not to compare those with NFRC results for complete windows. If you want to compare with European values, I suggest that you use the Cardinal Glass catalog that also has center-of-glass values. Center-of-glass U-values are on the order of 30% lower than whole window U-values (see same greenbuildingadvisor reference as above, especially the discussion following the article). That difference will explain much but not all of the European advantage that you always see.

I disagree that "0" is the better choice for the northern US. For the NFRC to use a delta-T of 70F, it takes into account a 0F outside temp and a 70F inside temp. I would like to see where in the Northern US does it average 0F? Nowhere but the Arctic Circle does it average 0F. Nowhere outside of northern Alaska where you might actually see a 70°F average delta-T during the heating season. The European delta-T is more realistic and that is just one factor why they are designed and perform better. This then plays into how the window panes are gaped between the spacer. A wider gap as found in European windows would see better energy benefits. NFRC calculations favor narrower spacing.

This then plays into frame hardware. Having wider gaps and having to carry triple panes, more robust frames are produced. Heavier duty hardware and latching mechanisms are used. I've seen and handled plenty of window frames and when you see and operate a European triple pane window, it's like a bank vault door.

You mentioned Cardinal Glass but European glass is a slightly different animal. Europeans make low-iron glass. The low iron glass allows them to achieve high SHGC and get better performance from the glazing units. Per that same GBA Blog article you referenced in your above post, after you made a comment on the blog regarding percentages, Bronwyn Barry stated the following:

Comparing NFRC test results with European window testing results is a complicated exercise in futility. I've tried it and concluded that the protocols vary enough that you're better off accepting that both protocols have merits, neither is better or worse and that they are simply different. Trying to generate a 'rule of thumb' or % deviation will get you in trouble. From my investigation, I found that NFRC numbers are linked to very specific glass packages. To ensure accurate comparisons you'd have to be sure that the IGU's you're simulating are exactly the same. Given that European glass manufacturers produce very different glass (more low iron, high SHGC) than what is typically made here in North America, - even by the same companies - you'll be calculating in the 'wishful thinking' territory.

Afterwards, Greg Smith stated: (emphasis mine)

"I could not agree more!!! As mentioned (unfortunately not adequately emphasized) in my original post, take the percentages that I listed with a grain of salt - they were in no way intended to be definitive, they were informal and intended to be anecdotal. I did a very poor job of clearly stating that. Echoing, and quoting, Bronwyn (and also mentioned in my original post), folks who are the real experts in this area emphsize that "Trying to generate a 'rule of thumb' or % deviation will get you in trouble."...Experts in this area have one bit of advice when it comes to trying to do direct comparisons...don't. 

Further confusing the issue I think was that the discussion did wander back and forth between glass package and whole window performance and there wasn't always a clear deliniation between them. Anyway, that the % comments got people talking and investigating further (as seen in the really excellent comments and follow up on this blog) was a real positive, but in retrospect I could have added a much better disclaimer than I did originally.

Then you have the spacer technology. Most US manufacturers are still using metal (aluminum or stainless steel) for the spacers, while Euro manufacturers have warm edge spacers (Swiss design) which don't introduce metal into their spacers.

Posted By Lbear on 07 Nov 2012 05:55 PM

I disagree that "0" is the better choice for the northern US. For the NFRC to use a delta-T of 70F, it takes into account a 0F outside temp and a 70F inside temp. I would like to see where in the Northern US does it average 0F? Nowhere but the Arctic Circle does it average 0F.
...snip...

I never stated that 0 F would be a better choice than 32 F for the outside temperature for window tests. However, there are reasons that 0 F might be considered a better choice. When you serve on an ASTM or ASHRAE committee to define a standardized test, you have to consider the opinions of many, not just your own. So I provided two reasons that would come up in a committee to choose the lower temperature. The reasons for your choice were obvious, and did not need repeating.

If the main interest was making sure that windows would function at the design temperature, and that the U-values were appropriate to sizing heating equipment, then you might choose the design temperature rather than the average winter temperature. In the northern U.S., design temperatures are around 0 F: Boston, 0 F; New York City, 0 F; Philadelphia, 0 F; Cleveland, 0 F; Chicago, -10 F; and Pittsburg, 0 F. I am sure that the comment would be made by someone in a committee, that "if it works down to the heating design temperature, then it will work across the board."

I have served on this type of committee before, but not on the committee for windows tests. If I did, I would have to listen all the discussion of the participants to arrive at a preference for conditions to be used in a standardized test.

My parerents house still has a full complement of pella casement windows from 1969. all still in great shape as are both the pella double 6 ft sliders with 2 fixed pannels each ie a 24 ft wide window wall that opens 12 ft wide. At 43 years old they still open smoothly. the house has 32 30X70 casements all still open and seal well. The only casement that failed did so because I put a large rock through it as a 8 year old. I have heard horror stories about newer pellas, but I installled a pella wood slider about 5 years ago that seemed to be very high quality. I woud not bang up pella too much

Posted By eric anderson on 10 Nov 2012 04:54 PM
  I have heard horror stories about newer pellas

Therein is the key to this issue. The Pella of yesteryear is not the Pella of today. Companies change and so does their quality control and designs. To save costs cheaper lumber is used, thinner parts are introduced, quicker assembly techniques, etc, and all of this then makes a huge difference in a window built today vs. a window built 10-20 years ago by the same company. Just do a Google search on Pella aluminum and wood windows and see the thousands of hits and read the thousands of complaints. Brand loyalty is a foolish notion in today's day and age.

I just walked through a 5 year old pella slider that looks good and works perfectly,(and was a pleasure to install.) Mayby that one was the exception and all the rest are crap? How many have you installed that resulted in callbacks? What window have you personaly had good luck with?

Posted By eric anderson on 10 Nov 2012 05:44 PM
  Mayby that one was the exception and all the rest are crap? How many have you installed that resulted in callbacks? What window have you personaly had good luck with?

I never stated that all of Pella's windows are bad, those are your words. Once again, do a Google search and read the complaints. One has to be careful because it's hit or miss with manufacturers and designs. A Sony TV might get great reviews and be very reliable but then a Sony DVD player will be junk. There are so many variables involved that the consumer has to research and research to see what will work and what will not work.

Here is a video that ties what I said all together : YOUTUBE VIDEO        VIDEO#2

Do an internet search on "____________ windows complaints" with the blank filled in with Anderson, Pella, Marvin, Serious, Sierra, Bee, Home Depot, Lowes, Champion, Window World, or anybody else that manufactures or installs a significant number of windows in North America and you will see plenty of complaints. Microsoft would also be a major player in the number of complaints if you filled in the blank with their name!

To minimize window problems, include plenty of roof overhang in the house design, use a good installer, and select window construction appropriate to your climate.

through out the years at our firm we have sped'd and used hundreds of pella windows, none of which, to my knowledge, have had any issues. And trust me, we would be the first to year about it. With clients you serve for many years, they always call the architect when a problem arrises with the building. If you research and dial in the root of many of the claims, it usually results in bad install. Bad flashing, not caulked, bottom is taped and caulked, no drop flashing, not installed plumb... the list goes on.

Posted By lzerarc on 12 Nov 2012 09:12 AM
through out the years at our firm we have sped'd and used hundreds of pella windows, none of which, to my knowledge, have had any issues. And trust me, we would be the first to year about it. With clients you serve for many years, they always call the architect when a problem arrises with the building. If you research and dial in the root of many of the claims, it usually results in bad install. Bad flashing, not caulked, bottom is taped and caulked, no drop flashing, not installed plumb... the list goes on.

Bingo.