Good performance numbers will speak of a good performing unit installed properly. Both go hand in hand. Be sure the ratings you are looking at are certified ratings. Some companies make performance claims, but can't back them up. The ratings also assume the unit is shut and locked. So if they use cheap, or poor hardware, they would still test good. I'm guessing from your login that you are in Hadley MA. I'm just up the road in Montague, so if you have some ideas of what you're looking for, I may be able to refer you to whomever is carrying that line. Good luck.

I only repair windows and can say I've reinstalled my fair share of misinstalled windows, correcting every problem imaginable. Rarely are windows installed per basic manufacturers instructions because either builders/remodelers think the way they did it for the last 1000 times is the best... or they don't have the time or money to do it right. I am in the process of replacing the windows in my own house. Now here is the kicker... I now have 4 types of windows 15 year old andersen, 15 yo weathershield, 15 yo no name, 1 year old Andersen. I get ice on the weathershields, lots of water on the no names, little condensation on old Andersens and the new Andersens are bone dry... all in the same house. Problems are almost always due to poor installation but no one wants to pay the price it costs for a great install. Oh well.

double entry - bump

{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!