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Musings of an Energy Nerd

What Windows Should I Buy?

Designers and builders talk about their favorite window brands

What's your favorite brand of window? Everyone seems to have a strong opinion on the issue. And builders love to talk about windows.
Image Credit: Image #1: Martin Holladay

Readers often post a simple question on our Q&A page: “What brand of window should I buy?” For an editor, it’s an exasperating question, because it’s unanswerable. The answer depends on a host of factors, including the buyer’s geographical location, performance expectations, budget, and personal sense of aesthetics.

Rather than attempting to answer the question, I decided to interview fourteen designers and builders of high-performance homes. I asked them, “What brand of window did you specify on recent high-performance projects — and why?”

Window basics

This article isn’t an introduction to high-performance windows. If you’re looking for that type of information, start with the following articles:

Background information on four window brands

It will be easier to understand some of the statements made below if readers have some basic background information on Intus Windows, Schüco Windows, Menck Windows, and Thermotech Fiberglass Windows.

Intus Windows are vinyl windows manufactured in Lithuania. Until recently, Intus windows were popular with American builders looking for high-performance triple-glazed windows at an affordable price. This year, Intus announced that it will no longer sell windows to builders of single-family homes in the U.S., so fans of Intus windows have been looking for a substitute manufacturer.

Schüco is a German manufacturer of window extrusions, window hardware, and window fabrication machinery. The company sells components to window fabricators all over the world. Since different fabricators use Schüco components in different ways, there is no such thing as a “Schüco window.” Anyone who is considering buying a “Schüco window” should learn the…

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  1. AntonioO | | #1

    Canadian fiberglass windows
    I was surprised that the Canadian fiberglass frame windows didn't make more of a showing. Did Thermotech sour opinions on the whole lot of them? Is their cost comparable to the European wood and vinyl frame manufacturers? What gives, Martin?

  2. GBA Editor
    Martin Holladay | | #2

    Response to Antonio Oliver
    All I did was interview people on this topic, so I don't really have an answer to your question.

    If you re-read the piece, you'll notice that John Semmelhack had good things to say about Accurate Dorwin.

    Jesse Thompson explained why he doesn't use Accurate Dorwin or Duxton.

    Rachel Wagner explained that she has specified both Accurate Dorwin and Duxton, and mentioned her disappointment with Duxton service.

  3. ethan_TFGStudio | | #3

    Inline Fiberglass, anyone?
    PVC is a problematic material, and is on the Living Building Challenge Red List of toxic materials. I know the question of material toxicity is controversial here at GBA, but it should be a part of any "Green Building" conversation.

    After my own exhaustive search for a high performance window not made of PVC that didn't break the budget, I found myself comparing Duxton, Inline, and Alpen.

    I settled on Inline Fiberglass. Duxton doesn't ship out East, and Inline provides profiles to Alpen. I also found that Alpen was not using a true triple pane but rather a suspended film, which has a sordid history which I was not willing to experiment with.

  4. user-6775258 | | #4

    matthews brothers
    im general, especially here in new england, im curious why there isn't more attention paid to matthews brothers? we're building in the white mountains and even at this stage of the game, im still reaching back out to vendors to get quotes (inline, alpen tyrol series, several other tilt and turns and euro-styles) and no one really touches MB in price, meaning many are 50% or more in cost, not even close.

    also, if you look at MB's passive glass glazing option their NFRC numbers surpass, in many cases they surpass the others in an overall ufactor, but also maintaining decent VT & SHGC, that im looking for on my south and west windows, hugely important to me. its not even that MB's numbers are amazing on those two fronts, it's that many others have really low VT and or SHGC, relatively speaking. so as a "package" i find MB to surpass them.

    also bears mentioning, we'll be installing solar and having a tight, double wall, liquid applied air barrier envelope, so im following the advice of a bit less into the windows, a bit more into the envelope and solar package.

    so what gives? what am i missing about matthews bros that makes them less popular, to the point of rarely being mentioned in my window research here and elsewhere? because they seem to be a really good value , however subjective that statement might be... yet not many mentions around here especially given they're made very locally to anyone building in NE

    i'm 90% committed to MB at this point (and likely driving my builder nuts as i'm sure he'd like this detail locked down by now) and trying to reassure myself i'm not overlooking the downside to MB or missing out on an "affordable" superior alternative.

    as ive said before on this site, window shopping is far and away the least favorite part of my build.

  5. GBA Editor
    Martin Holladay | | #5

    Response to John Williams
    Thanks for your review of Mathews Brothers windows.

    Q. "Why there isn't more attention paid to Mathews Brothers?"

    A. I don't really have an answer to your question, except to say, "GBA is paying attention to Mathews Brothers."

    For example, the article on this page includes a positive review of Mathews Brothers windows from Ben Southworth. For more information on Mathews Brothers windows, see the following GBA pages:

    Starting point for affordable triple-glazed windows?

    GBA Product Guide: Clara Starrett Vinyl Windows

    Two Builders Will Share Top Connecticut Prize

    Vinyl R5 windows (see Comment #1 from Ben Balcombe)

    Net-Zero-Energy House in a Kit

    One final point: I note that you misspelled "Mathews Brothers." The company spells "Mathews" with one T, not two. If you are performing a web search on the company, it helps to spell it right. That might explain why you concluded that GBA hasn't mentioned Mathews Brothers very much.

  6. MaryinLyme | | #6

    Mathews Brothers
    I'm exactly where John is. I'm an hour south but building a high performance house, 1850 sq ft and I'm perseverating over the windows. I've looked at them all and I'm so grateful for this recent discussion and opinions on the different brands. I'm going with either Wasco, Klearwall or Mathews Brothers. They're all pretty great price points for triple glazed. Klearwall seems to have the best specs with 2" thick windows but long lead time. Wasco has great specs but only comes in white and Mathews Brothers has good specs but max's out at 1 1/8" on the triple glazing. I'm not going with tilt and turn, just double hung.

    I've read here that 1 1/2" is optimum. Any thoughts on window thickness?
    Thanks, Mary

  7. GBA Editor
    Martin Holladay | | #7

    Response to Mary (Comment #6)
    Q. "Any thoughts on window thickness?"

    A. Are you asking about the thickness of the window frame or the thickness of the glazing? Traditionally, most U.S. window manufacturers made window frames that are about 4.5 inches deep (so that the frame extends from the interior surface of the drywall to the exterior surface of the plywood sheathing, assuming the use of 2x4 studs with no exterior rigid foam).

    If you are asking a question about glazing thickness, here is what I wrote on the topic for an article that was published in the October 2005 issue of Energy Design Update:

    "The gaps between the panes of high-performance triple glazing units are filled with an inert gas, almost always argon. For argon-filled glazing units, the optimal space between glazing layers is ½ inch, resulting in a triple-glazing unit thickness of 1 3/8 to 1 1/2 inch. Because thicker glazing units can be difficult to integrate into manageable sashes, some window manufacturers ... promote triple glazing units as thin as ½ inch. Such thin-gapped glazing units perform better with krypton gas than with argon gas. However, since krypton costs more than argon, some window manufacturers only offer argon, even in their thin glazing units; caveat emptor.

    "It is difficult to design a double-hung or slider window that accommodates full-thickness (1 3/8” or 1 1/2") triple glazing. Many manufacturers interested in window performance... prefer to stick with full-thickness triple glazing, and therefore offer triple glazing only for casement, awning, or fixed windows. Those looking for triple-glazed double-hungs have to settle for a compromise product with thin (½” or 1”) triple glazing."

  8. user-6870177 | | #8

    I would dearly love to see a graph of "U" vs. price for Energy Star windows. The lowest I have seen for a "U" value is about 0.123 = R 8.1; we bought regular Kolbe windows with U=.26 or R 3.85. Considering that the total for our windows was about $16K -- and that was with wood interiors, etc., I don't see the value. In contrast the non-window parts of the walls are R40.

    If energy efficient building is going to be the standard, then these exotic over-the-top solutions have to be identified as over-the-top and unnecessary.

    Mary Essary Hoyer, Salem, Iowa

  9. GBA Editor
    Martin Holladay | | #9

    Response to Mary Essary Hoyer (Comment #8)
    To read an article that echoes some of your conclusions, see Study Shows That Expensive Windows Yield Meager Energy Returns.

  10. jimg1126 | | #10

    Los Angeles
    Hello, I'm in Los Angeles building an 1800 square foot home. I would like as close to net zero as possible. Do I need triple pane windows or is this overkill for Southern California? It seems this article is written more from a cold weather climate perspective. Southern California is more a cooling dominated climate.

    I find the comment about Marvin windows interesting. I like their product but wonder if the quality lives up to the price.

  11. GBA Editor
    Martin Holladay | | #11

    Response to User 6872033
    User 687 etc.,
    First of all, can you tell us your name?

    Q. "Do I need triple pane windows or is this overkill for Southern California?"

    A. It's overkill. Stick with double-glazed windows with an Energy Star rating; note that Energy Star requirements vary by climate zone.

    For more information, see How to Order Windows.

  12. GBA Editor
    Martin Holladay | | #12

    Response to Darlene Rancourt
    With that much glass on the south elevation, I'd be worried about overheating in March and April.

    Once you've got the house built, report back and let us know whether the area of south glazing turned out right.


  13. Schieran | | #13

    South Face Glazing - Accomodations
    Wow, thank you for noticing! With the heating season occupying most of the year, we decided to let in the sun's heat and compensate for it in the few summer months.

    To your point about the shoulder of March and April, I do think we will have to learn which of our summer accommodations to utilize ~

    We will have personal-zone minisplits, but the wall assembly is designed to 'live and dry' in both directions without counting on central air. Prevailing winds in this location come from the south.

    The three foot overhang will protect the attic windows and some of the second floor, in the summer when the sun is 'high'. Blackout curtains are already planned for the second floor, so we will kick those in if we discover a need in the summer (master bedroom).

    The first floor has awnings planned, of the sort that may remain 3' extended 24/7 (during summer). There is an adjustable-louver pergola in front of the south/sunroom (which also has a 2' overhang on three sides).

    The walk out cellar south windows are 'protected' (ug!) by the deck above - we can only hope for good daylight!

    In winter, when the sun is lower, we hope the SHGC will let in the heat, and the tri-pane will help to keep it in!

    Cross-fingers, of course, as always . . .

  14. Expert Member
    Dana Dorsett | | #14

    "...personal-zone minisplits..." is probably a mistake @ Darlene
    The heating & cooling loads of individual rooms are usually well below the capacity of any ductless head even in code-min houses, and even more so in high performance houses. In multi-split systems (multiple heads, one compressor) the individual heads don't modulate (with a few exceptions), so in a high performance house you're guaranteed to short-cycle the ductless heads, and probably the compressor too. The result is a combination of lower comfort and lower efficiency.

    This 3- level house is probably better served by three separate mini-duct mini-splits, each on it's own fully modulating compressor, not a multi-split.

    This really requires a careful room by room, zone by zone load calculation & analysis, but the "ductless head per room" approach is almost never optimal, and usually costs more than a better optimized solution.

  15. Schieran | | #15

    Dettson Supreme with Alize heat pump?
    Dana, thank you (darnit, she said with a sigh). I 'hate' the idea of central cooling, and love the idea (over simplification here) of window units! So, in a modern house, I was going to use (multi zone) minisplits.

    I did get a third party/independent J load, and I gave it to Dettson to look at their (modulating) Supreme (Electric) and those so-cool 'Smart Ducts'. The initial blush is as you said - three systems, and the heavier cooling load driving the cfm/duct design (and unit sizes probably).

    The Sunroom was omitted entirely, probably because I heard nothing about zones. Round 2/review is coming up . . . and then, somehow, (THREE?) ventilation units (Dettson has that cool third wire and has been integrated, same ducts, with ventilation - albeit with a few return air adjustments) . . .

    As for our lifestyle issue - we are used to zero central and window units (that bleed out to larger semi-controlled areas) - - when one has central cooling, and an open central staircase, there is very little personal control. Basically, everyone gets A/C at night and no one during the day.

    Our lifestyle/expectations are in conflict with 'the best design' . . .

  16. GBA Editor
    Martin Holladay | | #16

    Response to Gregg Zuman
    Thanks for the information. (Note to GBA readers: You may remember Gregg Zuman. He's the homeowner whose project was profiled in a GBA article titled "Lead Paint and Old Clapboards.")

    GBA has listed Rieder windows in our Product Guide for a long time. Here is the link:
    Rieder KG Wood and Vinyl Passivhaus Windows.

    Rieder windows are manufactured in Ried im Zillertal, Austria. Here is a link to the website: Rieder GmbH.

    Note that North Americans are likely to misinterpret the U-factor you quoted. That's a center of glass U-factor, and it's not comparable to the whole-window U-factors shown on NFRC stickers in the U.S. The whole-window U-factors for Rieder windows are in the range of 0.14 to 0.23.

  17. Schieran | | #17

    Accurate Dorwin ordered for NH zone 5/6 residential
    Our window bid structure included 7 brands. I was interested in fiberglass-only frames because fiberglass conducts the least energy loss and has among the greatest durability..

    I was expecting Inline or Alpen to come out the other end, and I was excited about Cascadia's new line. I've had walls with less performance than Alpen! And I thought I loved tilt/turn, which is something that Inline even does with DOORS.

    Due to radius shapes in our window schedule (via segmented fiberglass, to simulate curves), we discovered that many 'fiberglass' windows have 'composite' areas to achieve radii, so several brands went off the list. Nothing wrong necessarily with composite, but my durability goal calls for uniformity of material, handling, maintenance etc.

    Ordering windows specific to your project involves a learning curve, even when you know what you are doing. Also, you may discover that you need a 'trim, modern' look patio door (as I did), or that your project benefits from a re-allocation of the glazing; for instance, two very tall casements become casement-over-awnings. Some companies just don't 'click' with you, don't educate or quickly respond perhaps - or, may not offer what you just discovered you wanted (sorry!). . . so a few more went off my list.

    In general, you will need to watch out for and specify your performance measures and your Tempered Glass requirements (per your applicable code), yourself. I had to create and present a crosswalk to our inspector, in order to avoid the dreaded 'rules of thumb' so prevalent in construction code compliance/practice.

    For our project, I would have been as pleased to use finalist Fibertec, but Accurate Dorwin edged them out for several reasons - ALL specific to my engineering temperament and project-specific needs.

    For both of these companies, and for our window schedule, we found a jump to all-triple-pane was less than $2000 more, than for south-face-only.

    We ordered all tri-pane.
    Performance Specs (awning version) are:
    The south face is SunGate400 with u .19, SHGC .39
    All other exposures are SolarBan60 with U .17, SHGC .23
    The fiberglass 'patio' doors are U .20, SHGC .14

    We received the factory-applied options that we wanted: (aluminum) universal brickmould (including for radii), nail flanges, and 3/4" drywall returns (for our site-built (painted) wood jamb extensions). Oak veneer (mainly Red) is available for the interior, but we ordered white inside and out. The locksets and hardware were easily comparable-to-superior.

    To achieve my end results, there were many reviews and explanations, in both directions. My Accurate Dorwin representative, Yuki Shiokawa, was top notch, responsive, and sent picture descriptions often.

    The delivery experience was as-described, well-packaged, slightly ahead of schedule, and seemless. For our construction season and glazing needs, ours was a 10 week window from the deposit date.

    The house stage is pre-mechanicals now; The building crew has about half of the windows from Accurate Dorwin installed and all is excellent at this point.

    If anyone is interested, other glazing specs on the project are:
    Sunroom (3 sides, N, E, and S exposures)
    U 24 SHGC 27 folding doors
    Cardinal 366, i89 dbl pane
    By Solar Innovations Inc

    Sunroom (E exposure)
    U 29 SHGC 23 large roof skylight
    SolarBan 90 dbl pane
    by Sunspace Designs Inc

    Commonwall separating Sunroom from Main house
    U 21, SHGC 41 slider door and windows
    Cardinal 272 i89 dbl pane
    By Solar Innovations Inc

  18. hudson_valley_gregg | | #18

    Thank you for the rigorous overview of window system options, Martin!

    I'm going with Austrian make RIEDER, imported via CEMBRA located here in the Hudson Valley. Of note, I have a "fossil fuel free materials" mission as a bottom line for the project, and these windows come as close as any I've seen on the market - and seem priced competitively with other higher-end makes.

    As an agent myself for a European manufacturer, I appreciate that CEMBRA - which is basically Thomas the agent - is a minimal go-between for a high-end European manufacturer as opposed to a service-oriented third party leveraging no-name Eastern European manufacturers (e.g., Yaro). At first, I was turned on by the notion of working with the people at Yaro and even Zola due to their customer service; however, I'm rather hands-on overall on my project (and I've got a groovy contractor collaborating), and Thomas has been great once we connected on the phone (another consideration) as opposed to email.

    I learned that the FINISH on windows is everything - sort of the secret sauce (read: skip paint if it pleases you). The Douglas fir tilt and turn wood windows (with aluminum sills) are infused only with a natural oil:

    3 layer wood construction. 3-step wood treatment to protect against fungus,
    water-damage and to insure uniform finish, all products used are water-
    soluble and environmentally friendly.

    Check out this U-value:

    Glass Type: TRIPLE GLAZING, Ug 0.10, SHGC-Value 51%

    I'll wind down for now. Suffice it to write that I'm eager to receive and install them (11 week turnaround after down payment from Austria).

  19. STEPHEN SHEEHY | | #19

    Opening windows?
    Darlene: I'd be interested in your rationale for having nearly every window openable.

  20. user-6775258 | | #20

    hi martin, yes my misspelling
    hi martin, yes my misspelling didn't help my case thank you and thank you for the add'l links!

  21. Expert Member
    KOHTA UENO | | #21

    Menck Windows

    Menck Windows are manufactured in Hamburg, Germany. A few years ago, the company announced plans to build a factory in Newport, Vermont, and hired U.S. representatives to solicit business at trade shows in New England. A few months later, Menck announced that it was cancelling its plans to build a Vermont factory. The abrupt change of plans left a bitter taste in the mouths of some U.S. customers.

    The full story is even more disappointing than this. The Vermont factory was cancelled due to running afoul of investment agreements (

    German-based Menck, which builds extra thick style thermal pane windows used throughout Europe, originally wanted to build a 75-employee window factory in Vermont, taking advantage of an EB-5 Immigrant Investor program that rewards foreign investors for generating jobs by investing in U.S. manufacturing facilities.

    But a conflict arose over the somewhat complex job creation formula. Use of imported woodworking equipment meant insufficient U.S. jobs were created in the establishment of the window factory to qualify under the EB-5 program.

    They then opened up a factory in Chicopee, MA... NESEA had a great tour of the place in the summer of 2015 (pics below). Awesome CNC machines and automated wood cutting. And they closed down in 2017 (

    CHICOPEE -- Menck USA, which opened a state-of-the-art window factory in Chicopee in May 2015 with the aid of state economic development incentives, has closed and is up for sale.

    The factory at 77 Champion Drive employed about 30 workers. Menck shut down the factory on Wednesday after investors decided not to put more money into the enterprise, according to a letter to creditors released to The Republican and MassLive Friday by attorney Michael B. Katz of the Springfield firm Bacon Wilson.

  22. GBA Editor
    Martin Holladay | | #22

    Response to Kohta Ueno
    Thanks for providing more details on the Menck disaster. I'm fully aware of the Vermont side of the story, since the so-called EB-5 fraud case (named for a visa program to lure foreign investment to the U.S.), involving a shady operator named Ariel Quiros, has been headline news in Vermont for years. Quiros is a con man who embezzled funds intended for economic development and used some of the money to buy himself a luxury condo in the Trump Tower building in New York City. Quiros is a villain who is familiar to everyone in my corner of Vermont, since he (and to a lesser extent, his partner Bill Stenger) managed to create economic devastation in downtown Newport and to push our two local ski areas, Burke Mountain and Jay Peak, close to bankruptcy.

    By all accounts, Quiros has an enormous ego. Even while he was fleecing Chinese investors for millions of dollars, while simultaneously funneling the money out the back door to fatten his personal bank account and fund his lavish lifestyle, Quiros found time to issue bizarre orders to his employees: the Burke Mountain ski area was re-named "Q Burke" (in honor of Quiros), and every bed in the new Burke hotel was equipped with a wooden headboard bearing a carved "Q" for guests to admire. After the Qurios scandal broke, the new hotel managers decided that replacing the headboards would be too expensive, so the carved Qs are still there.

    Like you, I knew that Menck had opened a factory in Massachusetts, but the details you provided help flesh out the story. I've edited my article to include information on the Massachusetts factory.

    I had several conversations with Menck representatives in New England, because I was eager to see a local factory making high-performance windows. I spoke on the phone with Todd Bachelder, who was hired by Menck to run the Newport factory -- until it was cancelled -- and I met Russell Chapman at a NESEA conference. Russell Chapman was hired as a Menck rep, and was soliciting window business on the trade show floor.

  23. Schieran | | #23

    Too many operable windows
    Response to Stephen Sheehy ~ your point is well taken (perhaps you noticed from the elevation?), there are too many operable windows. Not only did I miss the opportunity to get a better U factor, if I had more fixed units, but I agree it is doubtful we would open all these operables, anyway.

    My lesson, to share with others, is that toiling-away in isolation, I hid 'the forest' from myself while I was so focused and careful with 'each tree'. Every excuse for 'too many operable windows', in the end, sounds too trivial to cause such an oversight - but here I am, it does happen:

    I was not interested in a curtainwall face, so my 'teenager-like' architects were pouting and offered no alternatives. At All.

    Large windows were in my original, I'm-all-alone-poor-me, plan
    -- "Good" News:
    -- We had energy modeling results that supported the sizing
    -- Course, better if more fixed!
    -- There is a lakeview from that face
    -- There is intentional winter sun/heat - gathering
    -- The prevailing wind arrives into that face
    -- There are many fewer windows on the other exposures
    -- Some second story large casements will be appreciated as operable (but not all)

    Fiberglass frames rarely exceed 72" in height,
    -- so I had to use more mullioning to achieve old sizing
    -- duh, I didn't take advantage of the re-org to add 'fixed' portions!
    -- We actually found ourselves 'excited' about operating the easier-smaller, more weather-resistant, added awnings (and never thought to make the large casements fixed)!

    In a side note, recall that all-fiberglass frames (with the benefit of tiny thermal conductivity, like glass) use 'segmented' (straight) pieces to simulate a round shape. This can be a disconcerting feature of fiberglass frames. I have no problem with it, in my situation - attached is a photo of the installed Accurate Dorwin Inc. Tri-pane windows and 'Linear Style' (small frame) Doors, including the many segmented, simulated, arches.

    1. user-7564322 | | #26

      Darlene - how have the Accurate Dorwin windows performed so far?

      Considering theirs and Duxton for my project. Thanks

  24. ethan_TFGStudio | | #24

    never in a,million years...
    ... would I have drawn a facade with so many quarter rounds, but I have to admit that it kind of works.

  25. Expert Member
    MALCOLM TAYLOR | | #25

    Aesthetics aside, sloped or curved window heads are difficult to flash correctly, especially with a rain-screen cavity. You can't use an end-dam to move the water to the exterior.

  26. user-1116814560 | | #27

    Time to update this article….Cascadia in effect doenst Market any longer to single family residence builds. Plus it’s pricing is now extremely high. Great window no doubt, but not affordable …

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