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Community and Q&A

“Best” double pane window

Eweav | Posted in Energy Efficiency and Durability on

Hey all.  

Deeply appreciate the balanced perspective on this site.  We’re at window decision point on a small 600 sq ft cottage in eastern Tennessee.  The whole build is out of pocket, so it’s a balance between best practices, diy capabilities, recycled materials where appropriate, and long term value/efficiency.  

I’ve read through most of the articles on here and have landed on triple glaze is probably not necessary, esp for a small building like this in Tn.   

That said I want the a double pane that has a reputation of performing well over time.  Fiberglass would be awesome, but not sure if we can afford it.  Are there any options aside from vinyl for a tight budget, or are there manufacturers that build a quality foam filled vinyl?  


Am I just overthinking all of this?  We have a local Marvin dealer that I’ve asked for an estimate from so we’ll see how that comes back.  


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  1. kbentley57 | | #1


    There's really a large variance in quality between lineups even within a manufacturer. Assuming you're in the mountain region, where snow and shade persist for long periods in the winter, you'll probably want something with as low of a u factor and air infiltration number as you can afford. The solar heat gain coefficient would matter less to me, but I'd also want a low e coating on the exterior surface of the interior plane of glass. I haven't looked for such a combination myself, but surely it exists somewhere.

    Let us know what you find!

    1. Eweav | | #5

      Thanks, that seems to be what I’m finding out slowly. We’re in the Tennessee river valley so little snow and pretty exposed site, but on heat gain, our southwest and west facing windows.
      will only get 2 hours of direct sun… so definitely hoping for low E on those.

  2. [email protected] | | #2

    First consideration, do you have a preference of window material?

    Considering window material, if I am looking for a modern clean look that resembles metal windows but with less maintenance and much better energy performance than a metal window, I am going to look first at fiberglass. Fiberglass windows might be more versatile (color options and such) and are often the aesthetic choice when compared with vinyl and they require less maintenance than wood, and they should last a very long time on the whole.

    If I want a window with a more traditional look and feel, a window that radiates warmth, then I am going to look first at wood because wood still offers the best aesthetic in that role.

    But if I want maximum energy performance, often at a more reasonable price-point than the other options I am going to start with vinyl because generally speaking vinyl windows offer superior energy performance numbers when compared with wood or fiberglass.

    And keeping things less simple, there are also hybrids such as Fibrex, which is an Andersen-patented combination of vinyl and wood fiber that is the material used for Renewal and 100 series windows, as well as occasional bits and parts in other lines.

    As you consider the window sash/frame material, always keep in mind that the quality of the company that manufactures the window is much more important than the material that they use. Good companies make good windows and bad companies make bad windows no matter the material that they use to manufacture their product.

    There are some very good vinyl windows, some very middle of the road vinyl windows, and some very bad vinyl windows on-the-market. Fiberglass on the other hand (I suspect possibly because of the expense of the material and complexity and cost of the manufacturing process), tends to be better quality and hasn't yet caught on with the bottom feeder companies (that I have seen so far). And while fiberglass windows do tend to be more in the kinda-good to very good range in quality, once again this is all about the quality of the company and less about the material used to build the window.

    Like vinyl, there are very good wood windows, very average windows, and some really bad wood windows available. And with wood and vinyl windows price often does tend to indicate quality...but certainly not always.

    Fiberglass windows tend to be pricey and can be close to better wood of comparable "quality level" in price, and don't be surprised if a top quality vinyl window isn't cheap either. Top end vinyl windows can be comparable quality wood or fiberglass products in price.

    Just as bottom feeder wood windows shouldn't be compared with better quality wood products, junk vinyl should never be compared with higher end vinyl or fiberglass windows simply because it isn't a true apples to apples comparison. But when only looking at out-of-the-box numbers, even lower quality vinyl windows might offer energy performance numbers that are as good or better than either high end wood or fiberglass, assuming glass options being the same. Just don't count on bottom level vinyl windows to be around for very long once installed, despite the initially good looking performance values.

    How the windows are designed and how they are produced as components tends to favor vinyl over wood, fiberglass if energy performance is your primary concern then vinyl is going to be the winner pretty much every time assuming you are comparing apples again. But again stay away from bottom feeders despite their performance ratings.

    While I think the jury is still out on comparison of longevity and long-term performance of fiberglass versus wood or vinyl, forget the "vinyl windows all fail in 5 to 10 years" argument that is often tossed into conversations about the best material for windows, that's a load of excrement. Once again it's more about the company that made the window. That’s the real argument.

    With today's technology and manufacturing techniques some industry people don't even blink when talking 30 years and more useful life cycles no matter what material is used; with emphasis again (I just can't let go of it) on the initial quality of the manufacture. Junk is junk no matter who made it or what it's made of.

    Second consideration, glass options.

    I will preface this one with the consideration that you may or may not have a lot of glass options depending on company, price point, etc. But in the event you do have some say on the glass being offered, here are a few things to consider.

    Glass is glass is glass is on. It's what they do with the glass that's important in today's world.

    Simple ordinary monolithic glass used in residential windows might be 2.3mm (also known as single strength), 3mm (also known as double strength), 4mm, 5mm, 6mm or even 8mm thick depending on location, application, and most of all window company preference.

    Since you want a dual pane IGU using a warm edge spacer and LowE coating be sure to look at samples of the glass make up to make sure that you are happy with appearance and performance before you order the windows no matter who is building the window. Everyone is going to offer dual pane IGU, warm edge spacer, and LowE coated glass in their windows, so you won't have trouble finding what you want in that area.

    1. Expert Member
      MALCOLM TAYLOR | | #3


      I always learn a lot when you weigh in on window related posts.

      1. [email protected] | | #8


    2. Eweav | | #6

      Thanks for taking the time to lay all that out!
      Really a good overview. I think my best case preference all around is fiberglass, that said, we are doing a plaster system, so we like the idea of wood for a more traditional aesthetic, as we will have dividers/mullions.

      What constitutes a bottom feeder manu in your opinion? And are the Anderson, Pella, and Marvins of the world overall pretty reliable, or is there more research to be done between their product tiers?
      For example, price point has me leaning towards either Anderson 100s or Marvin Essentials.

      1. [email protected] | | #9

        I like Marvin, wood-clad and fiberglass. I also like Andersen wood-clad and I think that the 100 is a solid window as well.

        Any vinyl window that comes out of a big box, I wouldn't touch 0n a dare. As Walta said, in many cases you really do get what you pay for with windows. I would not use window world or any of the knock-off companies like window world and I would avoid the cut-rate brands in most cases, being very careful of any exceptions.

        There are over 1200 window companies in North America, and unfortunately a lot of people would say that the majority of them aren't very good, so research is vital before putting your money down.

        You have the big national companies like Andersen and Marvin, then regionals such as Anlin in California, Mathews Bros in Maine, or Innotech in Vancouver, plus many local companies that can be very small and might be good or might be awful.

        1. briancornwell | | #14

          Alpen High Performance Products as well.

    3. andyfrog | | #15

      What are the main structural differences between high and low end vinyl windows?

  3. walta100 | | #4

    I think window are one of the things that you get what you pay for.

    There are fabulous windows with astronomical price tags and useless windows for little money.

    If you going to live in this home for many years, I say push your budget and get bests windows you can afford. It will not be very long before you forget what the price was but the cheap windows will remind you daily about their poor qualities.

    80% of my house is the Silverline vinyl and 20% Marvin Integrity windows in the great room.


  4. Eweav | | #7

    Thanks all. Talking with my wife more, and it sounds like one driving factor is a ‘traditional cottage look’ so I think material is less of a factor as long as the window fits that.

    Personally, from a long term perspective fiberglass is attractive to me. As a woodworker, I have an appreciation for the fact that wood requires ‘maintenance’ and am okay with that as well.

    I’ve always hated the look of vinyl products but oberon476 is helping me see the light that it’s less about the material and more about how the build is executed, so as long as it looks good I’m open.

    Lastly, I’ve found a set of Pella wood clad casements on the ole marketplace. I’ve gotta say I’m pretty tempted as between those and a couple ‘surplus’ windows to round it out we could do this for 1000-1500. It is a sub 500 sq ft cottage, that will eventually become a tiny house so I’m considering lowering my ideals. The seller just can’t provide me with much info.

    Any thoughts on basically salvaged windows?

  5. [email protected] | | #10

    As a woodworker have you considered building your own windows? It's challenging but definitely doable, especially for a smaller project like yours. And you might find it fun and rewarding to do so.
    Are the salvage windows used? I would be very careful about using Pella in that circumstance. They use a roll-form vinyl cladding that has been known to result in some significant wood rot issues in the past. They now offer wood-clad with thicker pultruded aluminum that is still tight to the wood underlayment plus wood that has been treated with an aggressive anti-rot treatment, which might make an interesting discussion on it's own, but beyond that, older used windows might predate those changes and might have issues that you can't see.
    Vinyl windows are certainly controversial on a number of levels, and definitely not on everyone's list for a "green" product. But top quality are going to last a long time, have better energy performance than alternatives, and they can be recycled at the end of their life. There are trade-offs.

    1. Eweav | | #11

      Building my own would be the dream, as I’ve built doors in the past but never the chance to make windows. That has usually been my method when something is out of my budget. That said, I really don't have the time at the moment or a shop for that matter. Building a shop will hopefully come after this cottage.
      Yes from what I can tell they were removed for a remodel, but seller can’t provide any age info on them. That’s a great distinction on type and era of cladding. I’ll see if I can find out if it’s aluminum or not.
      -Hopefully getting a quote on alum clad for Anderson and Marvin today.

      1. Eweav | | #12

        I attached a couple photos of those Pellas just for kicks. They definitely need some love on the finish at very least. It looks like aluminum. We’ll see what he says.

        1. Eweav | | #13

          Only one at a time it seems

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