Is now the right time to buy replacement windows given new glass tech?
I ask because of an article in yesterday’s (3/21/25) Wall St Journal titled: “A Piece of Glass Thinner Than a Credit Card Could Solve America’s $25 Billion Energy Problem. New windows can insulate better than most walls, and some can even survive being hit with a two-by-four shot from a cannon”
Here’s the full article (behind a paywall, sorry…) https://www.wsj.com/business/corning-window-gorilla-glass-4f443b07?st=uwgtbs&reflink=desktopwebshare_permalink
It’s unclear from the article when this will be fully commercialized and they don’t mention the improvement to r or u value specifically. Just that this multi panels, laminated glass can potentially can be warmer than the surrounding walls.
I’ve got a deadline to make a decision so am looking for any concrete info on when these will be available and if it’s really that big an improvement over typical 2 pane glass with low e coating or just incremental….
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
pmf823,
And small modular fission reactors will power every house, and phase-change materials will store the energy in the structure that was 3d printed. If we waited for all the innovations that breathless articles in the WSJ promoted to us we would never get anything built.
I pay for a premium subscription to this site with the hope that people are more aware of new trends and can provide more specific details than your typical mass media reporter.
pmf823,
I didn't mean my response to be as cynical as it ended up sounding. But the building industry is constantly on the verge of all sorts of next big things that will transform everything, and if you look back, very few ever do come to fruition - or take a lot longer than we expect to do so.
I suspect that if this, or vacuum glass, or some other innovative glazing technology ends up transforming the industry, it would be possible to retrofit it to existing frames. Personally I wouldn't wait around in the hopes of that happening in the foreseeable future - but there is nothing about having been in the building trades for decades that makes me any more able to predict the future than you - except having observed the past record of similarly innovative products.
"it would be possible to retrofit it to existing frames."
If this is the case, then it's a non-issue for me. Just concerned newer tech windows that have layers of glass that's thicker overall and couldn't easily be swapped from a double paned.
As I mentioned to another poster, I may just call Alpen and see if anyone there knows.
Malcolm --
On the other hand, the building science in houses being built today is much better than even 20 years ago, and astonishingly better than what passed for quality in the 20th century.
Better insulated than the surrounding walls is laughable
Cut and paste product information so people can search other sites
Here are some of the details in the article:
"These new three- and four-pane windows can be even better insulators than the walls around them, but cost only about 20% more than standard energy-efficient windows. "
"Enter Corning, maker of the thin, tough Gorilla Glass that has helped make possible today’s mobile devices. In order to win over Steve Jobs and land Apple as a client when it first started making iPhones, Corning offered Apple a fresh twist on its existing process for making glass for LCD displays and other applications, which yielded a new kind of chemically strengthened glass."
"When three or even four layers of glass are put together, with inert gas in between, only the interior panes are the super-thin Corning panes, and they add little weight to the finished product.
When you go from a single air gap to the two or three that are possible with triple- and quad-pane windows, the insulating ability of a window can skyrocket, says Selkowitz, who has collaborated at the federally funded Lawrence Berkeley lab with Alpen, a Colorado-based maker of specialty windows, to research their capabilities."
I tried pasting parts of the article but it doesn't look like it went through.
Corning was mentioned as the manufacturer of Gorilla glass they developed for iphones that now has applications for windows. Also Alpen was sited as working with this tech so I suppose I could call them to see if I can get more specific info. But there's not much more mentioned.
Was just hoping someone here knew more about this already
It really doesn't matter how thick the glass is, it's the air gap(s) between the panes that are doing the "work" of insulating. Alpen, for example, uses suspended films -- not even glass -- in their very high performance windows. If someone comes up with some magically better performing inert gas, or a practical vacuum-insulated glass assembly with no visual issues, then I'm interested. Thickness of the glass panes doesn't make any real difference.
That line "the windows insulate better than walls" (paraphrasing a bit) is a joke. What kind of walls? The best windows out there in terms of R value are around R16 or so, and that's not even code minimum performance for most 2x4 walls these days (13+5ci). Most of us here on GBA are shooting for much higher R values in our walls than code minimum too.
They'd be better off talking about things that work today, like triple pane assemblies with thicker IGUs (which gives better insulating performance due to more and wider air spaces), and fancy Low-E coatings. Practical stuff that works right now. Any of those newer IGUs will far outperform an old clear glass double pane window.
Bill
The article implied the tech is already here. Just hasn't been commercialized yet. But Alpen is one of the manufacturers cited as working on it.
Sure would be easier if WSJ would let me post the actual article....
WSJ is not stupid, they have had a real paywall[not defeatable by javascript] for years
but you should be able to copy and paste a small piece of it to inform people what it is you are talking about
internally coated R6ish glass is really a whole different ballgame from code min glass.
IT is all about how much you want to spend.
pmf823,
Perhaps oddly - as I have no private browsing or anti-virus software at all on this computer - I have been able to access the whole article repeatedly.
I think they let you see a few articles a month as a way to encourage people to subscribe. I like to call that "drug dealer marketing": the first few are free, but then you gotta pay... :-D
They have, or at least, used to have, a $6/mo plan.
Bill
The big obstacle in making the IGU's thicker with more layers is the weight of the glass. Once you get to three layers the IGU's get so heavy that all sorts of practical issues start to arise.
If you could have glass that was the same strength at lower weight and thickness you could make four or more layers. That wouldn't have the R-value of a wall but it would be better than current windows.
The WSJ article describes something called solar heat gain - which is a property of existing commercially available windows that can be managed using multiple glass coatings. We have exactly these type of windows in our mountain home in snow country, and any quality window manufacturer can guide you on how to select a window with an appropriate SHGC (Solar Heat Gain Coefficient).
From the WSJ article:
"But this glass is so well insulated, it actually creates warmth in his living room: It admits the radiant heat of the low winter sun but prevents conductive heat loss through the window, says Schleicher."
Admitting radiant heat, and preventing conductive heat loss is nothing more than selecting the right coatings on a double- or triple-pane window.
Quadruple pane windows already exist, and they perform anywhere from R-12 to R-15. Yes, this is in the range of an insulated R-13 wall in a temperate region. But R-13 walls are nothing special and have been around since at least the 1960s. R-13 is less than an exterior wall built under today's codes.
The most recent innovation is in the glass unit thickness. The claim is that it is now possible to make a quadruple pane window that is as thick as a double pane using thinner glass and thin film. This may be what Alpen is working on. You can already buy triple and quadruple pane windows. Alpen wants to make them thinner.
And I wouldn't focus on just the glass. The seal design of the window (if it is operable), the window sash material (wood, metal, fiberglass, hybrid), the position of the window in the wall (near the inside, middle of the wall, or the outside), and how the wall insulation integrates with the window also have significant roles in how well the window performs.
In other words, the glass and the gas of the window is not the sole consideration. Window performance is the sum of the entire installation, not just the window.
This is a good read introducing some of these factors:
https://www.gsa.gov/system/files/25-Lightweight%20Quad-Pane%20Windows.pdf
The above article shows that a 500,000 sqf office can save about $6000 per year by upgrading from double-pane to quadruple-pane. The period for ROI is 20 years.
I'm guessing that these latest quadruple-pane windows are targeting large commercial office buildings that have the volume that can justify the up-front costs and the long-term savings, and perhaps passivhaus structures that are testing the limits of what is possible.
In summary, unless you have a very special requirement for thinner high-R windows, you can get what you need with standard double- or triple-pane windows and glass coatings for less money.
Thanks for the detailed response. You raise some interesting points and I'll check out that link. For the project I'm doing now, we're planning to fur out the 2x4 wall to 2x6 and add r23 rockwool. Seal up and air leaks. That and new fiberglass windows, even double paned, I know will make a huge difference from what we have now.
The problem with lotta-pane windows that are the same thickness as double pane windows is that you don't get the same increase in R value (as compared to a thicker assembly) because the air spaces are too thin. Ideal air spaces are clost to 1/2" or so, so if you only have a 1/8" air space, you won't get as much insulating value, regardless of the glass thickness used. You can up the R value somewhat in thinner assemblies by going with spendy exotic gasses like krypton, but you still won't get the performance you'd get with a so-called "full thickness" IGU. The thinner glass WOULD let you make more of the space between panes gas though (instead of glass), which WOULD give you a better R value per unit thickness than the same assembly with regular thickness glass panes though.
For a triple pane window with regular glass thickness, best performance is a 1-3/8" thick IGU with argon. A 1-1/8" thick IGU will perform similarly with a krypton gas fill, but will cost more. There are always tradeoffs, unfortunately.
BTW, my commercial customers all want ROIs of 5-10 years or so. I doubt I could sell an "upgrade" with a 20 year ROI. On a new project though, it would be a much easier upsell.
Bill
From a dollars and cents point of view the math for replacing windows has never worked and my guess is the price tag for this 4 pane window will not make the math work any better.
From what I read in the article I see no huge leaps in technology 4 layers filled with inert gas.
Making the thickness of each layer thinner seems unlikely to increase the R value.
I see little added value in the scratch and impact properties for use in most buildings.
The attached image is as technical as the article gets. More sizzle than steak.
Walta
We just lived through our first very cold winter in our newly bought 70's contemporary with lots of windows (almost 50% glazing in some rooms) that are aluminum framed and first generation thermopane double pane. I've quickly learned that ROI and renovating a home is for the most part an oxymoron given costs.... But I also learned the concept of 'comfort' after going through a winter of avoiding my cold living room and some other parts of the house. I will pay for comfort.
What grabbed my attention is the line about these new windows only costing 20% more. If it's 20% more than the mid range Marvin's I'm looking at, I might be able to make that work for my budget. I'm skeptical but have an order that is supposed to be made tomorrow, hence my query. I don't mind putting things off 2-3 years if there's a reason to.
Aluminum windows are a very poor performer from a thermal perspective, so it would be a lot easier to get a noticeable improvement from an upgrade to something with an thermally insulating frame. That's something of a special case.
For most people with basic double pane windows with any kind of frame other than aluminum, a window upgrade doesn't make financial sense unless the original windows are deteriorating to the point that they need to be replaced for that reason alone.
Bill
Thanks for your perspective re aluminum frames and your other comments. Very helpful.
I got a new window from Alpen a few years ago that had the glass that I assume the article is talking about (can't view it). It's a triple pane with the middle pane being thin. As I recall the U-factor quoted for it (0.14) was marginally better than for a similar window with the heat shield membrane. Nice window, but nothing earth shattering.
pjpfeiff,
I suspect the middle pane was made of the suspended film Bill refers to in his post #7 above, as the thin glass has not gone into production yet.