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Community and Q&A

Choosing High-Performance Windows

mpsterner | Posted in Energy Efficiency and Durability on

Finally moving forward on a zone 7 house build in Northern Wisconsin this spring and I need to settle on our window selection.

The house is 2,000 sf and we’re using a 2×6 dense pack cellulose wall with 4″ of mineral wool exterior insulation. We’ll have a combination of deep insulation in attic truss and 18″ vented i-joists for our roof system. We have not yet completed a REScheck or WUFI analysis but for the sake of the completion of our architectural drawings, I need to settle on our window package ASAP.

We’re after an aluminum-clad wood window for aesthetic and durability.

I’ve received quotes from countless companies but considering the product and service, we’ve narrowed it down to 2–Loewen and Zola. Here is the info:

Doug fir casements and fixed
Total window and door cost: $43,873
Airtightness: .03 cfm/ft2 @ 1920 Pa (40.10 psf)
u-value: 0.2 operable, 0.17 fixed
SHGC: 0.34-0.4
VT: 0.42-0.49

Finger-jointed pine tilt-and-turns (can upgrade to other woods)
Total window and door cost: $45,527 + $5,800 shipping = $51,327
Airtightness: .03 cfm/ft2 @ 4,800 Pa (100.25 psf)
u-value: 0.16 operable, 0.16 fixed
SHGC: 0.35-0.4
VT: 0.5

Seeing the samples, I expected the Zola performance to be quite a bit better than the Loewen package as they were much more robust. As far as my knowledge goes, Zola is only modestly better u-value and the same airtightness (though different design pressures) as listed here. Am I missing something?

Can anyone provide more insight on how these windows and doors compare? Zola is $7,454 more when you include the additional shipping cost and another $5,000 if I were to upgrade to douglas fir (like the Loewens).

How will these windows compare and perform in real life?


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  1. PAUL KUENN | | #1

    Looks like you're on the right track Michael!
    I'm waiting to see some input also from members. I used to like Wasco but they've changed in a very bad way. No help, poor salesmanship & deliveries of the wrong goods. Have you looked into 475s offerings?
    PK Appleton, WI

    1. mpsterner | | #2

      Hi Paul, greetings to another Wisconsinite!

      I did look into the 475 options–great windows and competitively priced, but the response times were just too long. I was concerned that any amount of communication would be slow and ultimately cause delay. Zola and Loewen have had incredible pre-sale communication and service.

      1. matt2021 | | #3

        I, too, have an interest in finding how performance windows for a four-season room project I have. I have been looking at Alpen's for now. When you and Paul mention the 475's, are you referring to windows being sold by 475 High Performance Building Supply? If so, the brand of windows they seem to sell is OptiWin. Is that right, or am I missing something? Thanks!

        1. mpsterner | | #4

          Hi Matt. Yes, that is correct.

          1. matt2021 | | #5

            Thank you!

  2. eagleeyeshawk | | #6


    Not to hijack your thread. Could you clarify how many windows you have, square footage of glass, triple pane etc? It will be helpful to see what you are getting for your money


    1. mpsterner | | #7

      Hi Eagleeyeshawk,
      You can see my window schedule attached. Yes, both options are triple pane.

      Looks like the windows and doors total 473 square feet, so they come in at the following:
      Loewen - $92.75/sf
      Zola Thermo Clad - $108.51

  3. eagleeyeshawk | | #8


    Thank you for sharing the schedule. Wow, I had no idea that the triple pane windows were that expensive. I’m glad you shared that information with us. Good luck with your decision. I will be rethinking our window budget!


    1. mpsterner | | #10

      Yes, they're expensive. Don't close the book on triple pane though! You can get uPVC triple pane tilt and turn for half the cost that I've outlined here. They're a lot less expensive than aluminum clad wood.

  4. BirchwoodBill | | #9

    Over in Minnesota, the Zola looked really good compared to Marvin and Andersen.

  5. mpsterner | | #11

    Thank you everyone!

    Are any building scientists or folks with a deep understanding of window performance able to help me understand what the real life difference is between these options and anything else I should be considering that I am not?

  6. brian_wiley | | #12

    Hi Michael, this may be old news to you, but I’ll pass it along incase it slipped by:

    I thought it did a really great job of translating the myriad specs into something relatable like comfort.

  7. creativedestruction | | #13

    Number of gaskets has an effect on the airtightness numbers. I can't speak to Loewen specifically but it's common for North American windows to only include one. My own casements have developed frost at the corners of the gasket, suggesting small air leakage (Pella fiberglass). Tilt turns often have multiple seals and multiple locking points ensuring tight consistent seal and resistance at higher wind pressures.

    U 0.16 to 0.2 isn't a whole lot different in energy savings but perhaps a little bit in condensation resistance if you plan to humidify for comfort. Manufacturers go to great lengths for those small incremental improvements below about U0.2. I bet you're basically seeing the thermal difference of the frame designs, less difference in center of glass performance.

    Just my $0.02. I'd splurge for the tilt turns myself not for energy savings which are meager, but just for the 'feel' and operation.

  8. jackofalltrades777 | | #14

    You're paying more for the aluminum and wood frames than you are for the triple pane IGU. Wood frame aluminum clad windows are very expensive, even in dual pane.

    Fiberglass or uPVC is your friend when it comes to window frames.

  9. lukasmpeter | | #15

    Matt Risinger did an episode on European high performance windows ordered through this outfit:
    If I remember correctly, the triple glazed European windows including container freight where cheaper than US products.
    I have no relationship with this European window rep, I am just baffled at the lousy value proposition of US windows.

    1. creativedestruction | | #16


      Point taken but I believe Loewen are Canadian and Zola are definitely not manufactured this side of the Atlantic.

  10. jackofalltrades777 | | #17

    Even in Europe, wood frame aluminum clad windows are pricey. They are just expensive to produce with the large wood frames and then the aluminum is not inexpensive either. That's why in Europe, triple pane in standard but so are uPVC frames.

    Price out triple pane in fiberglass or uPVC frames from a company like Alpen and you will see how affordable triple panes are vs wood frame aluminum clad windows that are imported from Europe.

  11. eagleeyeshawk | | #18


    I agree. What do you think the price differential is between a Loewen fiberglass window and the aluminum clad wood windows shown here? About 30% less? That’s still about $60/sqft.

    I actually saw some fiberglass modern Marvin windows the other day, double pane, u value 0.26. They looked quite slick and had decent specs. Was very tempted!

    1. jackofalltrades777 | | #19

      More like 40% savings when compared to Alpen fiberglass triple pane. A 3'0 x 4'0 fixed window with a U-Value of 0.16 is about the low to mid $50 per sqft range.

      1. eagleeyeshawk | | #21


        Thanks for the information. Very helpful!

  12. Jon_Lawrence | | #20

    I have European triple pane wood/alu-clad that worked out to $82/sf, but the dollar was really strong then. At the time Zola was about 10% more. The cheapest wood/alu-clad window was KlearWall, but I did not like their profiles. Intus had the best value fiberglass, but I don't believe they sell residential any more. I would not have an issue going fiberglass next time.

  13. T_Barker | | #22

    Nice windows! Can't beat Doug Fir aluminum clad.

    My two cents is, for the quality of building you're constructing I would personally be looking for U=0.11-0.12 windows. My first reaction was "Jesus, US$100/sq.ft. for R5 windows!". But I get the Doug Fir part.

    If you're willing to keep SHGC in the 0.34 range (which I agree with btw) I'm surprised you can't get VT up around 0.6. VT at 0.4-0.5 is noticeable in my opinion.

  14. tdbaugha | | #23

    Hey Mike, what windows did you go with and are you happy with your decision?

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