Let's start with the first thing you learned. It's incorrect. There is nothing superior about the base material of uPVC used in European windows vs. the uPVC used in American extrusions.

2nd thing, also incorrect. Much of the glass technology and evolution in this field has been driven by manufacturers that are based right here in the US.

3rd point, also incorrect. The standard whole unit R-Value is Europe is NOT an R8. You may see some COG numbers that will approach that, but as a total unit, the number of windows in Europe or the US that hit an R8, is few and far between. Bordering on non-existent.

I fear you have been taken in by some very good website writings. While the initial inquiry on your part is well served if it steers you away from your previously mentioned supplier for a custom build, the rest of your assertions are mostly incorrect.

Where you do see differences in European windows is that, on the average, they do stress better thermal resistance numbers as well as better air infiltration numbers. For the longest time, and still to this date in many cases, many US manufacturers didn't care about air leakage. That said, it has been a central point to our material selection criteria for over a decade now.

Also...many of the Euro-style operators are naturally going to more airtight as the manner in which they operate allows them to be compression locked against a full perimeter weatherstripping.

No offense intended with labeling some of your assertions as "incorrect", but I just want the information that may or may not be cited by future readers of the forums to be as accurate as possible.

Thank you for the replies. No offense taken since I did ask for different opinions from what I had gathered in my research. Your reply provided some very different ideas from what I have read and heard elsewhere.

As a novice in this area I'm not sure how to evaluate what I've read and heard when the information varies so much between different sources. How do I separate the wheat from the chaff?

There is a professional contractor who hosts a build show on youtube who is a huge advocate for European windows, he's even installing them in his own home. He and his cohost have many different videos where they talk about the advantages of European over American windows including offering superior performance statistics. They aren't the only source of those statistics though, almost every website and video discussing the advantages of European windows say the same thing. No offense intended but how does someone like me know who or what to believe? If the statistics aren't true, then how can so many professionals say that they are?

Could you elaborate on why you don't like Jeldwin Siteline and suggest alternatives for windows with wood interior? Who knew that choosing windows would be so complicated?

Your info would be more interesting with actual products and websites to compare. Generalizations like you've used don't do much to further comparative discussion. If you've done your research list the findings and sources you're relying on. The National Fenestration Rating Council has a directory to compare products. Certified Product Directory | National Fenestration Rating Council (nfrc.org)

Marvin Elevate has a wood interior with a fiberglass frame and exterior. Link.

I know of a builder (trying to be vague here) that really likes a certain product and recommends it on every project. He gets a percentage of the sale price of that product used on his projects. I find that a little bias.

The generalizations of "European windows" is problematic. I think there are about 45 countries in Europe. I assume in many of those countries they have several windows manufacturers. And just like anywhere, there are going to be good ones and bad ones. It sounds like you are being sold on a romanticized idea of "Europe" as somehow manufacturing things better than a manufacturer in the U.S. like Kolbe or Marvin. I'd also wonder at the feasibility of converting metric measurements to your U.S. home's cutouts, flashing, siding, etc.

I also remember @oberon476 stating that European performance values, are not figured the same way that US values are even though the terminology is often the same, meaning the values are often apples and oranges. Perhaps oberon will see this and pop in.

I was told the same thing about ratings. We ended up going with a true European window manufactured in Austria. Gorgeous product. They subsequently went out of business because they could not compete with the eastern European countries who also were manufactuing windows.

We could not find a comparable product stateside at the time. They are aluminum clad and wood interior, passive house certified. They were ridiculously expensive, but they are REALLY nicely made / high quality.

We are also in NC and used a company out of western NC to purchase / import. They were quite knowledgable and we're very happy with the product. They helped us order replacement glass and import when we had a large triple pane get broken.

If you are going for full passivhaus design, you need a designer that is going to understand all of the points of glazing and solar. There is a bunch of information on Cardinal regarding all of the glass options.

If you are building a house for efficiency, air tightness should be a huge part of the equation and there are plenty of American based companies that make really airtight windows. Again, operator type is going to also play a factor in decision.

https://www.cardinalcorp.com/technology/reference/loe-performance-stats/

{Quick heads up that I originally posted this thing but then didn't have a chance to review prior to posting it. I did came back to reread a couple hours later and decided to do a bit of editing for clarity, sentence structure, grammar, spelling, all the things that I generally mess up on first drafts. I didn't intentionally make any content changes, other than add comment on air infiltration, otherwise just some basic housekeeping. Sorry for causing any confusion.}

First disclaimer is that I am totally OCD on this subject so likely that my reply will be way too long but hopefully not totally convoluted.

David, all the replies that you have received have been really good, but the initial reply that you received from WoW was "take-it-to-the-bank" good, and while he totally hit every nail right on it's pointy head, I am going to add a bit more because - please refer to my first disclaimer.

When using the term "European windows", people are almost always actually referring specifically to tilt/turn or dual action windows. This is kind of comparable to preservationists saying "traditional windows" while thinking specifically of old double hung windows. The idea that European and tilt/turn are synonymous terms at least as often used) is important because as a design the tilt/turn has some advantages (and disadvantages) over other styles which in part end up being quoted as some of the major selling points for "European windows". And also that it brings me to my second disclaimer - I have tilt/turns in my house and I flat out love them, but my windows were not manufactured in Europe, rather they were made in western Canada using German vinyl extrusions and hardware with a triple pane glass pack made by a Cardinal IG plant in the US.

So why the big discrepancy in performance values between what European window advocates claim (such as contractor MR and his buddy Steve on YouTube - and really curious if they were one of your sources of misinformation) and what WoW commented on in his post? As millworkman pointed out, it's way more often than not an apples to oranges comparison when European advocates are bragging on how good their windows are when compared with anything made in North America or more specifically in the US.

Disclaimer three - I actually really like European windows (i.e. tilt/turns, but fixed and glass doors as well), I think that they make some great products, that combine high quality manufacturing with state-of-the-art technology. They tend to be big and to American standards bulky, which some people find aesthetically off-putting, and they are heavy as heck (both physically and aesthetically which could be good or bad depending on what people want. The problem to me is that when comparing European and North American windows the European advocates tend to "tilt the table" in order to prove just how much better the European windows are.

Testing for European window performance measures center-of-glass, edge-of-glass, sash, and frame as four separate data points. NFRC (North America window testing and certification agency) measures center-of-glass, edge-of-glass, and sash/frame combined as three separate data points, Edge-of-glass is the outer 2.5" perimeter of the IGU and anything not within that edge perimeter area is considered CoG.

Other differences include windows tested in Europe use a larger glass area than is used by NFRC. Since the CoG is warmer than the EoG it stands to reason that using a larger glass area results in more glass in the warmer part of the window, or better performance values when testing larger windows with more glass area versus smaller windows with less glass area.

And while NFRC uses zero degrees F as the cold end baseline when computing performance values, European testing uses 20°F as the cold end baseline. The warmer baseline in Europe inherently favors wider airspaces in performance calculations primarily due to convection current considerations, not so coincidently European windows tend to have wider airspaces which is an advantage in Euro testing but not when NFRC testing.

One real advantage of tilt/turn style windows, no matter where they are manufactured, and as WoW pointed out, is in air infiltration. Credit where due, in general European windows do a heck of a lot better job controlling air infiltration than most windows built on this side of the pond. This is a gap (pun intended, sorry) that not many companies over here pay nearly enough attention to but they are getting better and that's a big plus.

There is actually a very simple formula for converting metric European performance data into Imperial NFRC performance data, but unfortunately results obtained using the very simple formula are invalid because testing methods are not directly comparable,.

While using this simple formula does not give an accurate comparison result between the two different systems, it's still very commonly used (advertently or inadvertently) by people representing the superiority of European windows to compare Euro values to NFRC values. When you see R8 and R9 and R10 ascribed to European window performance numbers in certain videos and on certain websites you are seeing the European test results translated into Imperial (NFRC) using the formula I mentioned. Typically when these same windows are tested to NFRC standards in a direct comparison they tend to be more like R7 at the top end. Just as using CoG performance values to advertise total window system performance is not meaningful, converting European performance numbers to imperial is not meaningful when comparing those numbers to NFRC values.

In order to do an actual apples to apples comparison, the windows must be tested using one or the other measuring system, they cannot be compared by mathematically converting from one to the other. As mentioned earlier, the Euro measurement criteria tends to favor wider airspace while NFRC tends to favor slightly narrower spaces, but this doesn’t necessarily mean that you can simply drop a third lite between two other lites in a 7/8" dual IG and automatically expect to get great triple pane numbers, it's more of a generalization as part of an overall system.

Also please note that I specifically said "European windows", not "European-style" windows. My contention is that there is no inherent automatic advantage to using imported European windows vs comparable North American windows. When I say North American or NFRC I am absolutely including "European-style" or tilt/turn windows built in North America using North American glass packages and potentially a mixture of North American and/or European sash/frame/ hardware in the construction of the North American windows as comparables. There are only a few manufacturers of tilt/turn hardware (for sure Germany, elsewhere?), so even when buying from different countries in Europe it's possible that they are also using imported hardware rather than domestic.

There is another thread on Houzz that asked about Thermo-Tech windows made in the middle of nowhere Minnesota. This is a small regional company (not to be confused with ThermoTech in Canada) that probably isn't on too many people's radar, and honestly I don't know if they make a really good window or not (but what I see on their website is interesting in a good way). Anyway this small regional vinyl window manufacturer makes triple pane casement windows with R6.25 or U.16, and fixed units with R7.14 or U.14. That's not too bad and it's not unique. There are dozens if not hundreds of other small and medium and even large companies in US that can match that performance as measured using NFRC standards.

And per the contention that European windows have better light transmission? That's an easy one....NFRC computes total light transmission (and solar heat transmission) using the entire window, frame and all as the base. In other words while the window glass might have 80% visible light transmittance, the parts of the window that you can't see through are also counted and they have zero visible light transmittance. Overall window visible light transmittance might end up as maybe 40% or maybe 60% in that scenario - depending on the overall size of the window and percentage of glass area.

European windows list the glass-only visible light transmittance, they ignore frame, sash, muntin bars. What that means is that a 10x10 European window will have the same listed visible light transmittance as a 100x100 window. I think it's pretty obvious that putting a 10x10 window in a wall ain't gonna pass the same amount of visible light as well a 100x100 window.

So saying on a YouTube video (or on several YouTube videos) that European windows have an R8 with 70% visible light is either ignorant or is flat out knowingly lying...I won't comment further.

Given the incentive to do so companies like Marvin. Kolbe, Andersen and others could match anything coming out of Europe, but that’s not what most of the general public is asking for. However there are smaller often regional companies who fill that niche and do manufacture windows that can compare with European imports in basic energy performance that are appropriate to the part of the country that they call home.

Sorry so long, as I said I am totally OCD on this subject!

"Sorry so long, as I said I am totally OCD on this subject!"

Like I said, the man, the myth, the legend has spoken.

Yep. Oberon-1-Kenobi has spoken.

Are cliff's notes available yet on that comment??

They are at the publisher...

The abridged version.

When talking about European windows, 90%(+) people are referring specifically to tilt/turn or dual action windows.

European windows can be pretty amazing, but they are not the technological marvel that are decades ahead of their North American counterparts.

The apparent energy performance superiority that advocates claim is often smoke and mirrors resulting from an invalid interpretation of performance testing.

European manufacturers generally do a great job of paying attention to the small details and that is a plus.

European companies tend to be more focused on producing one window in two or three styles (fixed, operator, door) versus big NA window companies that might have multiple lines and multiple window styles that may hinder their ability in providing the type of attention to the small details that the European products are known for, but there are smaller (and some larger) NA companies that do a very good job at looking into the details, and companies that (maybe or maybe not intentionally) also follow the European model and produce just one product but are very good at that one product.

The biggest factor in the differences is in providing what the consumer wants (and often gov't regulations) call for.

Keeping in mind that these are primarily observations (except energy performance) and specifics can certainly vary.

All I will say is 22 yrs ago I was in the midst of a renovation for a client and the windows we wanted no one in NA made we had to order from Germany what I find is the US is very far behind stlye wise and Canada is a bit better but not up to the Europeans when it comes to style and innovations As for quality is is hard to compare when you are not comparing the same style and materials.

Maybe top of the line European windows are fabulous, but I have lived in standard tract housing in Europe and was unimpressed.

PCC, what style window are you talking about that is available in Europe but not in NA?

As I mentioned in my post, when talking about European windows 90%(+) are referring specifically to tilt/turns when describing the amazing technological marvel that they are supposed to be. And while T/T may arguably be the most efficient window on the market, they also tend to be very utilitarian (something some people like and some don't), and bulky or heavy, again opinions vary on how they are perceived, also some people don't like that they open inward potentially taking up floor space. But other than the T/T, which is now readily available all over NA, I can't think of a window style that is strictly European, so very curious what they are installing that is way ahead of NA in style and innovation.

My T/T's (Euro and NA hybrid built in Canada) are 16 years old and still perform like they were brand new, but there is a lot of frame and sash surrounding the glass that some people who see them will ask about.

So...while tilt and turn are certainly less readily available in the US vs. in Europe, there is nothing else about your performance list that is readily unavailable in US products. I love tilt and turns, but the home needs to be built around that operator style to accommodate that functionality.

That's not accurate though. Cardinal and the other US based glass manufacturers are just as much on the leading edge of the technology curve as any manufacturer in the world.

Vacuum glass, soon to be available in the US, will be the tip of the technological curve.

Did Eurpoe build to a higher efficiency standard in their homes in the last 20 years...sure. Do their selections of window operators (i.e. tilt and turn) make for a more airtight opening as compared to most of the US based double hungs...sure. That is more of a function of what style of windows are common in Europe more than a conscious efficiency decision on their part.

There are plenty of windows available for the mainstream American consumer that are top tier performers and can be used as part of high efficiency building. You don't need to ship product from Eurpoe to get a high efficiency window.

Guessing that whomever you were replying to deleted their post.. great response in any case