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Community and Q&A

Cardinal Glass Double-Pane IGUs

HFF | Posted in General Questions on

I am considering Cardinal Glass double pane IGU’s made with their LoE 366 glass (u=0.29). There is an option to add a 4th coating, called i89, that will reduce the u to 0.23 for an air-filled unit. Can anyone give me an idea of how much that i89 might add to the cost of the window? It has been difficult for me to get answers from my supplier. Climate zone 5 and I’m just trying to get a sense of the cost effectiveness of this added option.

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  1. jackofalltrades777 | | #1

    Condensation issues have been reported with the i89 coating with double pane windows. Ideally a true triple pane window will perform better as even the basic triple pane window will have a U-Value of 0.18 and a true triple pane will have better condensation ratings.

    In Europe and places like Germany, double pane windows are basically illegal to install in new builds. It's been triple pane for years. The USA is behind the times when it comes to energy efficient windows.

    To get pricing, you need to call your window manufacturer and get quotes. Otherwise, you as a homeowner will not be able to get windows directly from Cardinal as they DO NOT sell direct like that.

    In my opinion, just get triple pane windows if you really want to get best performance.

    1. niffoc | | #22

      "you need to call your window manufacturer"
      Andersen told me they only provide IGUs built into Andersen frames. Andersen rep said they do not provide standalone IGUs. Which window manufacturers provide standalone (made to order) Cardinal IGUs? Thanks!

      1. oberon476 | | #24

        None that I have ever heard of. Not saying it never happens, but it's going to be very rare.

      2. AdamT | | #25

        You can google "insulated glass unit manufacturers" and get a long list of IGU fabricators. One of them has an instant quote lookup where you can build a double or triple pane IGU (or window), add coatings and see the price impact:

  2. Mark_Nagel | | #2

    Doesn't it come down to what the required specs are?

    Perhaps I've not quite achieved the proper understanding, but it would seem that at some point pushing U-value will run into the point of diminishing returns: there's been a discussion of virtual windows (the ultimate in eliminating energy losses, as well as in eliminating weather damage).

    No offense to Europeans, but just because they don't allow double-pane that doesn't mean that double-pane is necessarily unable to meet a need. Europe pushed diesel vehicles hard (I have a couple, in which case I'm not bashing, I'm just pointing out facts) and we later learned that data was being manipulated. I don't like just tossing stuff out to be contradictory, but it seems like there's a bit of room in this "triple-pane or bust" approach.

    I'm spec'ing a house build and a PHIUS "prescriptive" suggests a 0.28 U value. There are double-pane windows that can do that. I'm welcome to any education on whether PHIUS requires triple glass. Most triples, however, really kill heat gain and transparency; for my tastes- I don't have a lot of days with sunshine and I WANT (stated to be just shy of "need") solar heating and to actually see it. If it was so obvious I'd have picked what I plan to use, but it's not, and I haven't.

    One other thing to note is that everything eventually fails. How readily available is any of the glass should you need replacement? Keep in mind that rarely does anything "fail" in a time of convenience.

    1. jackofalltrades777 | | #4


      A lot to unpack there but the podcast should answer 90% of your questions.

      In Germany, at their equivalent to a "Home Depot" big box store. You can find a triple pane windows sitting on a shelf in their window aisle, with a R-9 rating and it COSTS LESS than a cheaply built Jeld-Wen R-3 window sitting in a USA Home Depot aisle. In addition, they don't sell single or double hung windows, or even sliding windows in Germany and other parts of Europe. The reason? Those windows inherently leak tons of air and are very inefficient. They only sell "Tilt & Turn" windows for operable windows. They are super air tight and lock and seal like bank vault doors. A US casement is far more ideal to any sliding or hung window.

      As far as USA made triple pane windows, like those from Alpen. They have a SHGC in the 0.45 - 0.50 range. So it is not true that triple pane kills heat gain for those needing it in the colder Northern US climates. A window with that SHGC provides ample heat gain and sizing a window plays a large role also. As far as transparency goes. The Visible Light Transparency ratings in triple pane in high gain are in the the 0.60 - 0.70 range so that provides plenty of natural light. In Southern US states, a lower VT rating (0.40 range) is desired, as one doesn't want to have to wear sun glasses while indoors ;)

      1. Mark_Nagel | | #5

        Peter, yes, I've looked at/am looking at the Alpen windows. Low U values pretty much come with reduced transparency, or that's the numbers I've seen. I'll have to look again but I don't recall U values in the 0.28 to sub 0.28 range that have SHGC numbers in the 0.40-0.50 range.

        That windows are cheaper in Europe could be part of a subsidization program: they might not make double-pane; they might put tariffs on them. I don't know. Yes, I'd like to see better stuff here in the US (Eurpeans have a lot of great stuff that US markets do not), but for now things are pretty limited. I, like many I suppose, don't have deep pockets to snag on all the cutting edge things (to force a market shift in the US). Note that I wholeheartedly appreciate mandates to help push markets: it's one reason I'm contemplating building new (even though my current home is pretty efficient, compared to many around me, I worry that if I'm forced to give up my wood stove that life will really suck- I do NOT want to run my propane furnace at all).

        Good manufacturers can build good double-pane windows. Are they as good as triple-pane? No. But, the reality is is that triple-pane windows aren't all that affordable for the vast bulk of folks in the US.

        There's pretty-good, and then there's stellar. Anyone want to see what the world around me looks like? It's pretty much far superior to that of other locations, such as where my wife is from (Philippines), but it's still nowhere near the "stellar" end of things. I've been around the sun enough times to understand that the word "compromise" is a word that's heavily embedded in life. Identifying what gains and compromises one can endure/accept is the big trick.

  3. Deleted | | #6


  4. jackofalltrades777 | | #7

    Alpen offers a High Gain option with a U-Value of 0.16 and a SHGC of 0.48 with a VT of 0.62

    1. Mark_Nagel | | #19

      Peter, thanks for beating me to it :-) Yes, there's the one that seems to match up. But, as noted, there aren't many triples that do/can. I won't be finalizing, giving any feedback on this, until after I've hashed things with an architect (one that's familiar with Passive House designs).

  5. Expert Member
    BILL WICHERS | | #8

    It's worth noting that there are varying thicknesses of triple pane windows. The thinnest is made to basically fit a double pane window design as an "upgrade" to triple pane, but it doesn't really perform as well as a full-depth triple pane IGU due to the limited air spaces. 1-3/8" full depth triple pane IGUs perform best.

    It's also worth noting that much of Europe has a climate more like the northern US. Mandating windows for that type of climate for all of the US isn't a good idea, because it's in many ways wasted in the milder climate areas. Select products that fit the need in the local in which they're being installed. In northern areas, triple pane makes more sense. i89 can gain you some of the benefits of a triple pane at lower cost, but the comparison they make is with the "thin" 7/8" triple pane IGU. A full depth triple pane IGU will outperform a double pane window with i89.

    It will come down to how much are you willing to spend? The range of options is a basic triple pane on the low end, good double pane windows with i89 and thin triple pane windows in the middle, and full-depth 1-3/8" triple pane windows on the high end. The full depth triple pane windows are much heavier too, so keep that in mind, but they do offer the best cold weather performance.

    BTW, regarding diesel engines, the energy conversion efficiency is much higher. You will get better mileage with a diesel than with a gasoline engine regardless of any monkeying with engine controls. This is why all the big stuff (trucks, ships, big generators) have been diesel for nearly a century. The funny buisness with the numbers was all about emissions numbers, not fuel efficiency. A better regulatory program would have allowed the efficiency gains (lower fuel use per mile traveled) of diesel engines with more reasonable emissions targets. There are always tradeoffs in these things, and government regulators, especially when pushed by activists, often make the wrong decisions when the bigger picture is considered.


    1. b_coplin | | #9

      It's true that diesel is far more energy-dense than gasoline and inherently more efficient, but the larger benefits to the "big stuff" are the increased torque and longevity of diesel engines. The fact that diesel is often less expensive doesn't hurt, either.

      The "funny business" behind the VW emissions cheating scandal was a deliberate attempt to cheat emissions regulators not just in the United States, but also the EU. Real-world testing in the US revealed VW vehicles exceeding NOX limits by 5 to 30x:

      NOX has severe GWP implications, but is a pretty nasty pollutant generally, setting GWP aside. But perhaps you have some ideas as to what would constitute more "reasonable" emissions targets and/or regulatory programs, bearing in mind other manufacturers of diesel vehicles are able to meet current and historical limits?

      1. JC72 | | #10

        NOX isn't really a GHG, but it contributes to ground level ozone which is an issue.

        The greater the reduction in NOX the worse the fuel efficiency of a diesel engine. This is because NOX generation is proportional to combustion temps and higher combustion temps result in greater fuel efficiency. The primary pollution control system for this is EGR (Exhaust Gas Recirculation) which re-routes some exhaust gases back into the engine in order to reduce combustion temps which as I said early reduces NOX. The secondary and third pollution control systems are DPF and SCR.
        So yes other automakers could pass the emissions tests but they could not pass and get the same fuel efficiency that the VW diesel engines were getting.

        The problem with Europe is that their tax structure incentivizes the wrong fuel. Diesel is taxed at a lower rate and the tax structure on vehicle is based upon engine displacement (2 liter, 3 liter engines, etc) rather than model. Diesels are the worst option for around town driving because they're dirtier at low speeds/idling but they still get better MPG's vs gasoline.

      2. Expert Member
        BILL WICHERS | | #11

        John pretty much beat me to it. VW was trading off emissions for better fuel economy (efficiency), and, as I understand it, bet acceleration performance. Engineering is all about tradeoffs. Reduced emissions often means lower overall system efficiency. It's actually possible to do things in such a way that the reduced emissions requiremens imposed by regulations can result in more overall emissions since more fuel is needed to achieve the same result. Basically you reduce the efficiency so much to meet an emissions target that the reduction in efficiency more than offsets the reduction in emissions when the entire system is considered.

        An example of how this could happen, simplified a lot to make things easy to see:
        Imagine a city mandates "all electric" homes, no natural gas use. A new home is built using electric resistance baseboard heat. What happens? That home uses MORE natural gas and produces MORE emissions overall. Why does that happen? Using natural gas directly for heat maybe get into the 90+ percent effiency range in terms of converting energy in the natural gas to useful heat. With the electric system, you have the conversion losses of the power plant (typically 70+% of fuel energy is lost as "waste" heat), and losses in the power transmission lines (5-10% more losses), so to produce the same useful heat in that house, you could be using 4x more natural gas. The regulation intending to eliminate natural gas use has now resulted in MUCH more natural gas use.

        Yes, other things can come into play (using a heat pump instead of resistance, electricity primarily from hydroelectric sources, etc.), but I wanted to make the example as simple as possible so that it's easily understood.

        I mention this because I see it a lot in my work. I work as a consulting engineer with large projects. There are a a LOT of counterproductive regulations. A classic one in Michgian involves diesel generator fuel fill stations. The state has a LOT of requirements for these fill stations to minimize the possibility of a spill. Everyone agrees that's a good idea, you don't want fuel spills. The problem is that they've so over complicated things, that when the fuel crew comes to fill the tank, they can't figure out the fill station so they bypass it completely, filling through a vent or threaded cap somewhere. The end result is the well-intentioned regulation to limit the possibility of spill has greatly INCREASED the possibility of a spill in reality.

        It is always important to consider and UNDERSTAND the ENTIRE system and not be overly focused on any one part when you're trying to acheive a goal. This goes for system efficiency, and it goes for anything else "green" too. How exactly you get to that goal can involve many paths and tradeoffs based on what's important for any particular project, but it's always important to consider the entire system to get the best overall result.


        1. JC72 | | #12


          VW was under pricing pressure because they didn't want to develop their own SCR (i.e. Urea) system or use the version from another automaker (Mercedes Benz?). They went EGR/DPF only and when that didn't work they left the test program active so it would pass emissions while on the test bed.

          Some will consider the fiasco a blessing in disguise because the fallout has essentially resulted in the banning of ICE passenger cars in Europe within the near future.

        2. b_coplin | | #15

          VW conspired to lie to governmental bodies and to the public at large. If VW wants to make a business decision to trade off emissions for fuel efficiency, that's fine--they just can't sell these products in the US or the EU.

          If you think these regulations are counter-productive or onerous, I'd be interested to know how you would propose to compensate the public for (perhaps) unquantifiable and certainly unevenly distributed harm to their health for private efficiency gains due to increased NOX emissions.

          I agree the Energy Tax Directive is in some ways problematic, often made worse by individual member states, and demonstrates the limits of financial instruments. The bigger problem, in my view, is that air pollution policies are distinct from climate policies.

          1. Expert Member
            BILL WICHERS | | #17

            >"compensate the public for (perhaps) unquantifiable and certainly unevenly distributed harm to their health for private"

            You just inadvertantly mentioned they primary problem with anything like that: it's unquantifiable, and, thus, arbitrary. In VW's case, they are in a tricky spot: both low emissions AND fuel economy are desireable outcomes. They're also mutually exclusively to an extent. What do you do?

            Fuel economy standards have resulted in lighter weight automotive designs. This has increased the likelyhood of crash fatalities in many cases (this is true, you can find data to back it up). So there is a link between increased fuel economy standards and increased death rates for car crashes. You want better fuel economy, but you also want safe vehicles, so what do you do?

            My point is that physics just is. It doesn't care about you, me, or anyone. You can't legislate around physics. Engineering is all about tradeoffs and dealing with the realities of the physical world. Regulatory bodies are usually politicized, they don't have the same requirements to be realistic. The end result is a lot of well-meaning, but poorly thought out and counterproductive regulations. I deal with this all the time with my work, unfortunately, and it's very frustrating. There are things like emissions scrubber requirements for power plants that literally cost billions of dollars, where that same money could achieve better efficiency gains if invested elsewhere -- there would be GREATER benefit if that money (resources) was put somewhere else.

            Don't ever believe that gov't mandated regulations are the best way to achieve anything. I'm not saying that I have a better solution, just that it is folly to think that gov't is always the best solution. Attempts to politicize the world of physics and engineering is always doomed to fail, and we'll get a lot of wasted time and resources along the way to more people realizing that fact.


          2. b_coplin | | #20

            "You just inadvertently mentioned the primary problem with anything like that: it's unquantifiable, and, thus, arbitrary."

            I asked you to propose a regulation that would compensate members of the public effected by increased emissions in exchange for (privately realized) efficiency gains, in lieu of what exists. We agree that such a regulation is probably unworkable. In the absence of such a regulation, a limit on tailpipe emissions strikes me the most reasonable and workable solution, as it is (or can be) based on life sciences. This does add cost, but that is always part of design criterion.

            I agree that government regulation is not the only means by which to achieve a desired outcome (i.e. clean air) or even necessarily the best. That said, industry has a long and -at best- checkered history of regulating its own behavior. At least government has the advantage of accountability to the public.

            *Edited to add*


            I'm sorry for the worm hole on Dieselgate, of all things. It has absolutely nothing to do with your question about windows.

  6. HFF | | #13

    Thanks all for a wide-ranging discussion. Back to the question at hand.

    Peter L, you make a passionate case for triple pane, but my thoughts are falling more in line with those of Mark. Consider my particular case. With 7,200 degree days (pretty chilly), I calculate heat loss through my proposed 22 windows (glass area 250 sq feet), assuming u=0.29 to be 3670 kWh. At $0.11/kWh, running a heat pump with COP of 3, my annual cost for u=0.29 glazing is $135. If I go with a triple pane, u=0.16 in this example, I'm saving $60 a year. Over a span of 20 years, this comes to $55 per window. I simply cannot see the value in the substantial cost increase for high-end triple pane. Your remarks about Europe are interesting, but I suspect Mark is correct that state-mandated market distortions contribute more to this situation than any reasonable quantitative analysis.

    I'm curious what others may think. A recent GBA article cited upwards of $400/sq. ft. for a "pretty good house". This is an obscene amount of money to spend on a house, and I'm concerned that green building technologies may only be within the grasp of the wealthiest among us.

    1. JC72 | | #14

      "I'm curious what others may think. A recent GBA article cited upwards of $400/sq. ft. for a "pretty good house". This is a obscene amount of money to spend on a house, and I'm concerned that green building technologies may only be within the grasp of the wealthiest among us."

      - This is commonly the case unless the owner has the ability to contribute a substantial amount of their own "sweat equity". Depending on ones perspective and climate as building codes get tighter the cost gap should get smaller but of course some of that is because the price of new goes up.

    2. Expert Member
      BILL WICHERS | | #16

      It's worth noting that triple pane windows tend to be comfort advantages as well, since you don't feet a cold draft off of them the way you might under certain conditions with a double pane window. It's not entirely a questions of monetary savings on fuel costs over the life of the window.

      If you want to go to the max on energy efficiency, stuff gets expensive. Many of the products out there are well into the point of diminishing returns in that regard, so you should look if there are any other benefits besides just costs savings in those cases when making your final decisions. In some ways this is like picking higher trim levels: nicer floors don't save any money, but they might make you enjoy your house more, and only you can put a price on things like that.


    3. Expert Member
      Michael Maines | | #18

      A Pretty Good House should not cost much more than other high-quality houses. If a PGH near you is $400/sf, then a conventionally-built home might cost $380/sf. That does add up to an obscene amount of money, at least at the sizes Americans are used to. That does not mean that green building is necessarily out of reach; it means that part of green building is building smaller, and not considering building a brand new single family home to be a necessity. It's a luxury. Most of the world's population lives in multi-family housing of some sort, and with far less square footage per person than Americans are used to. Address those issues first, and the modest upcharge to be "green" won't be a problem.

  7. niffoc | | #21

    From which retailer are you purchasing Cardinal IGUs? Will these IGUs be installed into the old window frames? Will the Cardinal IGU retailer also complete IGU installation? I'd like to do the same but cannot find a retailer (zipcode 32259) who will provide Cardinal IGUs. Thanks!

  8. oberon476 | | #23

    Cardinal IGU's are intended for window manufacturers and are not sold to the general public, even to contractors, directly.

    Cardinal warrants the IGU to the window company, not to the window consumer, and that warranty does include consideration as to how the IGU was installed into the sash as well as materials used (sealants, setting blocks, etc.) during the glazing process, something that can't be controlled should IGU's be sold outside of an actual window company.

    With over 500,000,000 IGU's currently under warranty and an IGU field failure rate of .2% at 20 years (warranty is for 20 years but actually the XL spacer system is now at 30 years and the failure rate is still steady at .2%), Cardinal pays a lot of attention to where and how their IGU's are being used.

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