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Community and Q&A

Trying to be green and vinyl windows

AtTheBeach | Posted in General Questions on

I’ve been lurking here – what a great site and articulate, passionate group. We are planning a 1350 sq ft single story house (box) with loft in northern Vermont – a summer/fall vacation home. Infrequent winter visits but would keep the heat at 50. Pretty Good House is our goal (net zero, SIPs, tight house kits, etc. seem too expensive for our area). Tilt & turn feels like overkill so was thinking triple-glazed Marvins wood/aluminum would be good enough, but then became interested in Mathews Brothers “Sanford Hills” line. They look beautiful and energy efficient but are vinyl. I get that they are “better” than the old vinyl windows of yore but my question is can vinyl windows really have a place in green(ish) building, especially if they are not tilt & turns? The reading is confusing on the subject.


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  1. Expert Member
    BILL WICHERS | | #1

    If you go with triple pane windows, make sure you’re getting full width 1-3/8” IGUs. If you are getting the 7/8” IGUs, you’re better off with double pane windows and the i89 coating. A double pane with i89 will be more cost effective than a skinny triple pane and will have similar performance. Triple pane windows really need the wider air gaps of the full width IGUs to really see a performance improvement from the third pane.

    Many people have good luck with the newer vinyl windows. I prefer Fiberglass myself, but it’s more expensive and there are a lot less options.


    1. gusfhb | | #3

      Does anyone in this country actually make triple pane that thick?
      Cardinal[9 years ago] would only go up to about 1- 3/32,they were literally not tooled to make glass any thicker. And yeah, they listed thicker on their website then

      It is annoying because large glass tends to be non operable, so thickness/weight is not very important. and you can save more energy on larger glass.

      I mean, wouldn't 2 15 mm spaces be better, given the physics.....

      1. Expert Member
        BILL WICHERS | | #4

        1-3/8" IGUs are orderable from many window manufacturers so someone must be making them :-) I do believe Cardinal IS now making them, probably as a result of more demand for energy efficient assemblies.

        You are certainly correct too, triple pane makes the most sense in large, inoperable windows where there is a high amount of glass area compared to the overall area of the window when the frame is included. In smaller windows, the ratio is less (there is more frame relative to the amount of glass), so the benefit to the triple pane IGU is less.

        Large picture windows and sliding glass doors are where the big triple pane assemblies are best. In smaller windows it's more of a judgement call.


  2. Expert Member
    Michael Maines | | #2

    Ruth, I agree that it's easy to find conflicting opinions when it comes to vinyl (aka PVC) windows. I have not yet used Mathews Bros Sanford Hills line but they are made near me and I've checked them out at local lumberyards. I'm not sure what they cost but I bet they are not far off from Logic tilt/turns, which are uPVC (vinyl) and also made in the northeast (Pennsylvania).

    Both Logic and Mathews Bros are on the higher end of the quality spectrum, with gaskets that are mechanically locked into place--that is very important if you're considering PVC windows. Cheap vinyl windows use adhesive to hold some of the gaskets in place, and the adhesive fails eventually and the gaskets slide out of position. Logic has much beefier window frames and sash frames, typical of tilt/turn windows, which are also better insulated and easier to add additional insulation that American-style windows like Mathews Bros'. But for the kind of house you want to build, they are probably fine.

    As for vinyl vs. other materials, the main issue with vinyl, in my opinion, is that manufacturing releases a lot of dioxins that are environmental and health nightmares. If the cost savings mean that you can afford other energy improvements or lower carbon materials, they may be worth considering.

  3. BobMaynes | | #5

    Full disclosure: I work for Mathews Brothers, but what I'm posting here is my personal opinion based on my 38-year career in the window business.

    Based on the location of your home, you'd certainly want to consider triple glazed units, but I wouldn't necessarily recommend them, especially if your choose our Sanford Hills series. With a standard 3/4" Clear/Argon/Low-e dual glazed unit, we exceed Energy Star 6.0 requirements. Triple glazed will certainly improve on that metric, but since you don't anticipate year-round living, I question whether it's worth the investment.

    I realize Tilt and Turn windows look sexy, and the Germans (who call them "Dreikipfenster") have been promoting them in the US since they first discovered the US market in the 70s. Personally, I believe they (and most consumers) are more in love with the hardware than they are with the window. This is due to one major design flaw of the window: the harder the wind blows, the weaker the seal, since the window opens to the inside of the home. Never mind that you can't use traditional North American window treatments and still open the windows. Never mind that they usually don't come with the capacity of having an insect screen installed. That fact alone makes a Casement window a much better choice than a Tilt/Turn.

    With regard to some of the conversation in this thread regarding Insulating Glass Unit (IGU) thickness, all marketing hyperbole aside, the most efficient dual glazed IGU is 3/4", not 7/8" or 1". Reason for this is that the dead-air chamber between lites of glass is too narrow to allow any significant convection currents from establishing within. In the same token, the most efficient triple-glazed thickness is 1-1/8" asymmetrical.

    As for PVC as a framing material, the USGBC has long ago abandoned its reservations about PVC in green building, especially when it relates to windows, for many reasons, not the least of which are energy savings (both in production and in use), reduced maintenance, and improved building life-cycle.

    1. Expert Member
      Michael Maines | | #6

      Robert, can you share your average up-charge to go from dual glazed to triple glazed? Energy Star 6.0 sounds good but in our zone 6 climate it only requires U-0.27, which is the same as R-3.7 and barely better than code minimum (U-0.32 for the 2015 IRC; U-0.30 for 2018), while triple glazed units come in at anywhere from R-6 to R-11.

      The financial savings may or may not make triple glazing a good investment, but they will save money, and also provide greatly improved comfort and condensation/mold resistance, especially on larger units. I installed Mathews Brothers casement windows when I renovated my kitchen (double glazed) and I know you have competitive pricing. While it may be hard to justify going from your double glazed to triple glazed, if someone is considering something like Marvin Elevate double glazed, I bet your triple-glazing would look like a good value in comparison.

      Have you operated European or Euro-style tilt/turns? The hardware and gasketing is impressive. Although it's true that wind blowing against the windows is working against the gasketing, but it would take quite a wind to break the seal.

      1. AtTheBeach | | #8

        I may be reading the Marvin Integrity (now Elevate I think) product performance numbers incorrectly, but it looks like the “middle U value” 28x47 casement tripane low e is 1.40 while a similar Sanford Hills is .20 - could that be right?

        1. BobMaynes | | #10

          That can't be right... U-Factors are 1.00 or lower. While many people try to extrapolate an R-Value by using the U-Factor (1/U+R), this method is only an approximation. WINDOWS DO NOT HAVE R VALUES! That being established, a lot of manufacturers promote an R Value, as it's easier for the consumer to understand. But that's not even a possibility here, as that would be a U-Factor of about 0.71... and I can almost guarantee Marvin does not make a window that inefficient.

        2. Expert Member
          Michael Maines | | #13

          Ruth, Marvin Elevate (formerly Marvin Integrity Wood/Ultrex) has U-values around 0.20 as well:

  4. AtTheBeach | | #7

    Thanks all. I do feel like a dog chasing its tail as I try to educate myself. One decision affects the next. The mini-split heating saves on $ and fossil fuels but won’t do the job well if the house isn’t tight enough, wood windows are the most sustainable but supposedly the least effective, thermal ratings on the Sanford Hills have great u values but not-so-great solar gain numbers, triple panes cost more but cut down on condensation, builders have relationships with local lumberyards and we don’t want to drive the builder crazy chasing brands he may have never worked with. And of course budget affects the marital happiness factor... where’s the performance sticker for THAT!

    1. BobMaynes | | #12

      First, if this is a new build (as opposed to a remodel), unless your builder is a real lunkhead, you'll get a tight home, so the split is a very good choice since you'll only need to cool the home maybe 5 days total in the summer.

      Wood windows, sadly, are not the most sustainable, and this is coming from a company who made wood windows for 165 years! Wood windows required far more energy to produce and maintain than PVC or Fiberglass, and have a much shorter life expectancy. The Sanford Hills have MULTIPLE glazing options, depending on elevation exposure vis-a-vis the sun. Northern exposures would naturally want higher SHGC numbers than Southers exposures. For this reason, we stock multiple types of Low-e, depending on what you want to see. Remember, the 5 metrics being measured by the NFRC are frequently at odds with each other, so it's a real balancing act. See our S4 brochure, which explains this better, here:

      As I wrote in response to another post on this thread, as long as you avoid S4 glazing (see brochure above), you shouldn't need to worry about CRF, even with a dual glazed unit. Not sure what lumberyard your builder works with; we distribute as far north as Hanover in the east and Rutland in the west. Chances are, though, unless you're way up there, he's heard of us.

  5. BobMaynes | | #9

    Depending on the unit configuration and size, generally 10-12% upcharge for triple vs. dual.

    Energy Star has stratified the country into 4 climate zones: North, North-Central, South-Central and South, so I'm not sure what you're referring to when you say "Zone 6". However, "barely meeting" is still, at the end of the day, meeting the criteria, right? It's like being barely pregnant...

    While triple glazing certainly saves money, my point was return-on-investment, given the purpose of the building... why use resources when they're not needed? And, I'm not sure I agree with your assessment that they'll provide improved condensation resistance.

    The reason for my concern about your CRF judgement is that under the parameters of Energy Star 6.0, window manufacturers sometimes have to "game the system" by resorting to what's called S4 ("Roomside") Low-e. They do this because it's the only way they can get their U-Factor under 0.27. Unfortunately, this method also dramatically reduces the CRF down into the 40s and lower. Not good in a predominantly heating (North or North-Central) climate zone. We actually published a small informational brochure about the dangers of S4 glazing, which you can view here:

    Finally, not only have I operated many Tilt/Turn windows, when I worked for a German-American window company in the 80s, I made them in both Aluminum and PVC. Well, truth be told, we had the tooling and the extrusions to make a PVC, one, but never got an order for one. The aluminum ones were few and far between, and exclusively commercial projects. And yes, the hardware is impressive (hence my statement that the Germans are in love with the hardware), but other than the gee-whiz factor, I see little to recommend it as an energy efficient window, after all, EPDM (or any compression) gaskets do take a set, lose their flexibility over time and UV exposure, and will allow for leakage. One thing I did not mention about the window is that it's VERY sensitive to installation methods. Even slightly out of level, square and plumb and it won't operate well, won't lock well and won't seal well. And when you have a heavy panel swinging out of the plane of the wall, that can spell real trouble.

    1. Expert Member
      Michael Maines | | #11

      Robert, designers, architects and builders all over the country have to conform to their local building codes, almost always based on the International Residential Code (IRC). Here in Maine we are currently required to use the 2006 IRC, but hopefully that will change to the 2015 IRC soon. In Maine we are in climate zone 6 (as determined by the department of energy and the IRC): Table 1102.1.2 shows the thermal requirements for each zone.

      Meeting code minimum is the worst house you can legally build. It's like passing school with a D average. Most of us on this site are going for A or B grades. U-0.27 is not bad but it's also not particularly good either. Call it a C. It's fine for some projects but there are benefits to lower U-values.

      Why use resources where they aren't needed? You could ask why pay for stone countertops when plastic laminate will do; why drive a BMW when a Honda will do, why pay for steak when beans will do. There are both perceived and real benefits to paying more for higher quality and higher comfort levels.

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