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Litezone Windows up to R22

rockies63 | Posted in General Questions on

Has anyone used Litezone windows, out of Edmonton AB Canada?

Apparently they have insulating qualities up to R22.

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  1. Expert Member
    BILL WICHERS | | #1

    Looks like the same suspended film technology Alpen uses. Alpen claims up to R10. I'm a little suspicious of the claim of R22 that Litezone makes (which is equivalent to U 0.05), which seems awfully high. Aside from that, I can't claim any particular experience with their products.


    1. Expert Member
      MALCOLM TAYLOR | | #2

      Crazy if true. Why have walls?

      1. Expert Member
        BILL WICHERS | | #4

        True :-)

        I wonder what their VT numbers might be on those really high R value windows. My guess is not too much -- they are probably so dark as to look like smoked glass. There is no free lunch in the engineering world, unfortunately.


        1. Greg_Clarahan | | #17

          ​To achieve very high window R-values a glass unit will necessarily have a lower visible light transmission (VLT). Because the human eye will adjust to the amount of available light, most people will not notice a reduction in VLT until it falls below about 30%. LiteZone® L1079 glass units with R22G and R19W will have a VLT of about 25%, better than many tinted windows with much lower insulating value. People who have installed LiteZone® L0679 glass units (4.4" thick) with R17G, R14W and 35% VLT, have been very happy with the VLT. With slightly less insulating value VLT of around 40% or higher can be achieved. See

    2. Greg_Clarahan | | #16

      The R22G and R19W values are derived using Window 6.3 and Therm 6.3 software from Lawrence Berkeley National Laboratory, Berkeley, CA, and are based on NFRC 100-2010 weather conditions for a 1.2 m x 1.5 m (~4 ft. x ~5 ft.) window using LiteZone® L1079 insulating glass. The thermal performance modelled by this software has been verified by independent testing in accordance with "ASTM C1199-14 Thermal Test". You can see the test report at

  2. Expert Member
    NICK KEENAN | | #3

    Their highest performing window is 7.5" thick. It has two layers of glass and eight layers of film. They report a center-of-glass "R-value range" of 10.6 to 21.7 ( )

    I'm not sure what "R-value range" means. But the R-value per inch is that of mediocre windows. Although if they can make high-R windows by making them extra thick, good for them.

    1. charlie_sullivan | | #6

      From a performance perspective, the thickness can be a virtue. It means that there is less thermal bridging through the framing around the rough-opening or through the window bucks.

      I'm guessing that you can order it with different coatings on the film resulting in different center-0f-glass R-values ranging from 10.6 (with higher VT and SHGC) to 21.7 (with lower VT and SHGC).

      Note also the * in the table meaning those aren't actually avaiable--the max is 4 films and 2 layers of glass, for 6 panes and 5 air spaces, for R-6.4 to R-14.3 whole window.

    2. Greg_Clarahan | | #18

      Each of the 13 LiteZone® product groups shown in the data sheet linked, is distinguished by the number of suspended PET films layers (1 to 8 films), the size of the gaps between each layer and the overall glass unit thickness (1.75” to 7.5” thick using 6 mm glass lites). Performance within each product group then varies depending on the number and type of low-e coats used. The maximum overall window insulating value achieved for each product group ranges from R5.7 to R18.7. The glass unit thicknesses shown are based on using 6 mm glass lites. If thinner glass lites are appropriate for the intended application then the glass unit thickness can be reduced accordingly.

      Some of the product groups, marked with an asterisk, are not yet available because we have not yet made all the required investment in tooling and equipment to commercially manufacture those products. Our highest performing product currently available is LiteZone® L0679 insulating glass (line 9 in the table) which uses 4 suspended films to achieve up to R17.2G (U=0.0.58G) and R14.3W (U=0.070W) and a SHGC of 0.153 (NFRC Method).

      LiteZone® embraces the need to have a thick IGU construction to solve the problem of thermal transmission at the edge of glass, and through the frame around the IGU.

  3. [email protected] | | #5

    Anyone can make a multi-chambered IGU in order to achieve eye-popping U value numbers, the trick is making it last for any significant length of time.

    Three basic objectives; is it practical, is it affordable, is it effective. If it meets those three requisites it can work. If it doesn't then it’s not an option, it's a gimmick.

    1. Greg_Clarahan | | #19

      Making a multi-chambered IGU must overcome several very challenging technical problems, including among others:
      • Adding glass layers soon creates a serious weight problem.
      • Increasing the thickness of the IGU to accommodated addition layers results in huge air pressures within in the IGU on hot days that can cause glass breakage and premature seal failures.
      • Increasing the thickness of the IGU and increasing the temperature differential through the IGU assembly greatly increases thermal stress that can result in premature seal failures.

      Achieving extreme longevity for LiteZone® was as an important object as achieving its very high insulating values. LiteZone® has been successfully designed to have an expected life of more than 60 years.
      • All materials are stable and durable
      • All materials have similar coefficients of linear thermal expansion
      • Film suspension system applies almost no stress to film by using a proprietary spring suspension hidden within the spacer
      • Only air is used
      – Instead of trying to entrap a low conductive gas such as argon, krypton or xenon
      – No concerns with declining performance or decompression problems as argon, krypton or xenon escape from the glass unit over its life
      • Pressure equalized to minimize stress on the edge seal
      • Fiberglass spacer is exceedingly strong and highly insulating
      • Stronger structural connection to glass lites
      • Connections to glass lites are flexible
      • Only two edge seals to establish and maintain
      • Stainless steel foil wrap stops all water vapour transmission into unit

      Because of its long life, LiteZone® will have the lowest life cycle costs.

  4. pjpfeiff | | #7

    The story is that they use air-fill with some sort of breather tube that does not allow water vapor in but allows pressure to equalize, and that's what allows the units to be so thick. Also the films are held by springs (I think) that exert less force than the usual tech. The claim is a 60+ year life. I recently got a quote from them to replace a picture window as a frameless install. I have 2x4 walls so it wasn't one of their really thick IGUs...but still probably would have had an R-value similar to my walls.

    Anyway, I wanted to try out their product to see if perhaps I'd like to use more of it in a new build we intend to do one day. I very nearly went with them immediately because they were so responsive (which seems to be a rare thing these days). But shipping to me in Virginia was just too much for this small project. The price for the product itself was quite reasonable, though.

    Here is another video from Fine Homebuilding:

    And they were mentioned on this site here:

    1. Greg_Clarahan | | #20

      The internationally patented pressure equalization system uses a permanent small breather tube to allow air to enter and leave the IGU through a conduit contained within the spacer which prevents water vapour from entering the unit. This system needs no servicing during the life of the IGU and installs into window frames the same as a conventional IGU.

      The film suspension system uses springs, hidden within the spacer. The film essential floats within the spacer, biaxially held taut by the springs under low stress, and can expand and contract with changing temperatures independently of the IGU.

  5. [email protected] | | #8

    Since these are IGU numbers and not whole window numbers, Cardinal as an example, has several different constructions that achieve U .11 or R 9 in standard triple pane IGU configurations, and they can (and do) build quads at (certain) customer request, but quads are not considered a standard offering.

    1. Expert Member
      NICK KEENAN | | #9

      Put two of those back-to-back and you've got R-18 and it's not 7.5 inches thick.

      1. pjpfeiff | | #10

        You'd have to make sure you got an airtight and vapor-tight seal between them, though, right? Maybe that's not hard? But then I wonder if there would be complications arising from pressure differences between the IGUs and ambient. It's also not clear to me that the R-values of IGUs in series would add arithmetically. If I could get Therm to work on my computer it would be an interesting thing to simulate.

        1. Expert Member
          BILL WICHERS | | #12

          No, not really. Ideally you'd want an airtight seal, but even if they are close enough together to restrict convection currents you'll see a gain in R value by stacking the window assemblies.

          R values are additive, it doesn't matter if it's windows or fiberglass batts. Two R19 batts stacked on top of one another gives you R38. Two R5 windows stacked up will give you R10. You might not fully achieve that total R value due to thermal bridging of the frame, but that's not because the math of R values doesn't work -- it's because you have multiple components in the overall assembly. The same thing happens in wall assemblies or anything else comprised of more than one type of material.


          1. pjpfeiff | | #13

            I was thinking airtight because the inner surface of the outer window would get cold and be liable to have condensation issues if air (and therefore water vapor) is allowed to get to it.

            One reason I thought that window R-values might not add simply is due to this article:

            If designing for different outdoor temperatures leads to different gaps between lites in an IGU, then it seems the R-value of an IGU must be temperature (or delta-temperature) dependent. And if that is the case then putting two windows back to back means that neither one ever experiences its design conditions. Then again I guess you have to think of the two windows as a system rather than independent components. I'll have to think about this some more.

          2. Expert Member
            BILL WICHERS | | #14

            The R value of any insulating material, except for vacuum, is somewhat temperature dependent. This is best known in relation to polyiso being derated in cold weather, but it affects other things too -- mineral wool batts perform slightly BETTER in colder weather, for example, in terms of R value. This isn't a unique property of an IGU, it's a property of the air that is what is doing the actual insulating in the IGU.

            Condensation is something to be avoided, but it isn't part of the R value issue.

            If stacking two IDENTICAL windows, then you double the R value. This is the old "all else being equal" thing that is important when doing any kind of scientific work. You have to hold as many variables constant as you can, otherwise your end result is meaningless, or at least lets you draw incorrect conclusions my mistake. In any scientific experiement, which is essentially what we're talking about here, it's very important to make sure the variable you're measuring is the ONLY variable that is changing -- you MUST make sure ALL other things are held constant between samples.


      2. Greg_Clarahan | | #23

        Embracing a thicker IGU is the key to solving the problem of windows being the weak link in building envelope thermal performance. It makes sense to use high performing thick LiteZone® IGUs in the very thick walls of today’s energy efficient buildings (instead of low performing thin IGUs). Incorporating a 7.5” thick IGU is not an issue in a high-performance wall that often is 12 inches or even 16 inches thick. What is the sense in having an R50 or R60, thick wall, and then creating a thermal hole using maybe R6 or R7 windows (and less after the inert gas leaks out and much less at the frames). By using thicker, higher performing LiteZone® IGUs the wall systems may not need to be so thick and expensive to achieve the desired overall wall thermal performance.

        By putting two R9 triple pane units back-to back, you will introduce several technical problems. The space between the two IGUs may have a problem with condensation. Allowing that space to vent may control the moisture but will reduce thermal performance. There is a potential overheating problem which could put the IGUs under severe stress and increase the risk of premature seal failures. The insulating values will be significantly less after the inert gas escapes from the IGUs.

        LiteZone® can achieve R17 center of glass, using 4 suspended films, in a 4.4” thick L0679 IGU designed to have an expected life of more than 60 years. See photos here:

    2. Greg_Clarahan | | #21

      The LiteZone® performance value ranges include data for center of glass as well as the overall window insulating values based on a generic fixed wood window. Some of the issues with conventional triple pane IGUs include:
      • A triple pane that achieves R9 center of glass requires a room side low-e which introduces potential issues. All the published LiteZone® performance values are before incorporating a room side low-e coat.
      • A high-performance triple pane IGU requires the entrapment of an inert gas, which will escape from the IGU over time causing a reduction in thermal performance and may cause the IGU to become decompressed.
      • Shipping triple pane IGUs long distances through different geographic elevations, with varying atmospheric pressures, require capillary tubes to allow the IGU to pressure equalize. This will result in the partial loss of the inert gas during such transportation.
      • A high-performance triple pane IGU, because it is only about 1.75” thick in a commercial application, will have a frame performance of only around R3 to R4, with significant thermal losses at the IGU edge and through the frame around the IGU. The poor performance at the edge of glass will cause small windows to have an overall insulating value much worse than what is published and modelled for a window that is 4’ by 5’. These triple pane windows can still have problems with cold frames and even condensation in cold weather with high relative humidity.
      • Although the quality varies greatly, triple pane IGUs historically have demonstrated a relatively short life and a much shorter life expectancy than double pane IGUs (because they are under much more stress). Large triple pane IGUs facing south, enduring the thermal stresses from solar load, will not do very well compared to small triple pane IGUs facing north.

      Quad pane IGUs have a weight problem and are under even more stress than triple pane IGUs and therefore have an even shorter life expectancy.

  6. [email protected] | | #11

    The triple in my earlier reply is about 1-3/8" total depth.

    And just like two sheets of R-4 insulation stacked one behind the other can be added together to achieve R-8, in the same sense adding an additional (unconnected) triple IGU behind an existing triple IGU would by definition double the R-value (plus the addition of the R-value of the space between them). While real world stacking of IG units isn't quite that simple, technically the math works.

    The basic idea of using 4 or 5 or 6 layers within the IG does make perfect sense U-factor energy-performance-wise, while equalizing pressure between the spaces is also sound engineering practice (Cardinal drills a tiny hole in the corner of the center lite in a triple IGU for the same reason), I am skeptical of their claim of a proprietary method of allowing outside air into their IG space by separating out the moisture to admit only dry air inside though.

    Also allowing outside air into the IGU space seems to negate the possibility of using LowE coatings, so that while they would have a great U factor, and assuming that they don't use LowE coatings, then what would be their method of controlling radiant heat gain and loss through the glazing?

    1. charlie_sullivan | | #15

      Low-E coatings work just fine with air between panes. You do even better when you combine a fill gas with low E. But that's a separate benefit, not part of how low E works.

    2. Greg_Clarahan | | #25

      The suspended films usually have low-e coats but can be uncoated depending on the performance and optical values desired. Typically, the exterior glass lite has a low-e on surface #2. The air allowed into the glass unit is kept dry by the proprietary pressure equalization system to ensure there is no condensation within the glass unit and no deterioration of the low-e coats.

  7. [email protected] | | #22

    I do not know if the construction described in their patent exactly matches their final construction method but it may describe the broad strokes.

    The spring suspension, film handling, and overall assembly process must have been very difficult to figure out.

    The long channels in the frame filled with desiccant are really clever. I wondered how desiccant could last for 60 years but I guess if there is a really long path for air to pass through then it is possible. I was initially imagining a little beef jerky packet of desiccant and thought there was no way it would work!

    If the assembly is not too trade secret I would love to see a video.

  8. Greg_Clarahan | | #24

    The air must travel in close proximity to the desiccant contained in the very long path created by connecting in series the pressure equalization conduits within the fiberglass spacers. This ensures the desiccant has enough time to act on and adsorb any moisture in the air. As a result, only dry air can enter the internal cavities within a LiteZone® IGU. The individual cavities within a LiteZone® IGU are also pressure equalized to each other.

    The life of the desiccant contained within the pressure equalization conduit is much longer than what might be expected. This is because when temperatures rise causing the internal air to expand and the IGU to exhale, the warmer internal air will have a lower water vapour pressure than when it was inhaled. As the warmer, now relatively dryer air travels through the conduit, it will re-adsorb moisture that was previously picked up by the desiccant and expel it to the outside. A great deal of work has been done on the LiteZone® proprietary pressure equalization system and on the expected life of the desiccant. The life of the desiccant is at least 60 years and, in most cases, more than 100 years.

    The manufacturing processes were difficult to figure and are confidential, however, the company has successfully established commercial production of high quality LiteZone® insulating glass units that it can ship anywhere in the world.

  9. Greg_Clarahan | | #26

    Many hundreds of LiteZone® insulating glass units have been manufactured and installed in buildings since 2015. The first units were manufactured in our small prototyping facility before our current plant was commissioned in late 2019. To date, no LiteZone® glass unit has had an edge seal failure.

    Our in-house “water submersion test”, found that no measurable quantity of water had entered the test glass unit after being submerged in water for more than 2.5 years. No other insulating glass unit could survive this test. You can see a description and photos of this test here:

  10. rockies63 | | #27

    One thing not discussed here (but briefly touched on on their Litezone website) is that their glass units are made available for installation into another window manufacturers frames. Which companies have the best frames for this thickness of glass unit? What frame material is best?

    Initially I had the impression that Litezone units were only suited for fixed windows (they can be installed without using a traditional metal, pvc or wood frame) but can they be utilized for casement, awning or slider units? How is this done?

    1. pjpfeiff | | #28

      The only operable examples I've seen (online) are tilt/turn and lift & slide doors. Fenstur says on their website they'll use LiteZone units up to 72 mm thick, and Matt Risinger has a video about one such door here:

  11. Greg_Clarahan | | #29

    LiteZone® can be made in thicknesses that will fit into conventional operable window frames. For example, using ¼” glass lites, LiteZone® L0365 units are 1.75” thick, L0379 units are 2.02” thick and L0465 units are 2.22” thick. Using thinner glass lites were appropriate will reduce these thicknesses. For example, LiteZone® L0365 can be made only 1.51” thick using 1/8” glass lites.

    Fenstur Windows & Doors in Duncan, BC can supply fixed and operable wood windows using LiteZone® L0479, L0465, L0379 and L0365 insulating glass units. The L0465 unit (2 suspended films, 2.2” thick) can achieve up to R9.9G, R8.0W, with a SHGC of 0.180. The L0479 unit (2 suspended films, 2.8” thick) can achieve up to R10.3G, R8.7W, with a SHGC of 0.180, but with a warmer edge condition and better visible light transmission than the L0465 unit. Fenstur can also supply lift and slide wood patio doors using the L0465 units in the active leaf and L0479 units in the fixed leaf. See photos here:

    Duxton Windows & Doors in Winnipeg, MB can supply fiberglass windows that can accept up to 5.5” thick LiteZone® insulating glass in their fixed windows (i.e. line items 1 to 10 on the data sheet). The L0465 unit can be used in Duxton’s swing doors and the L0379 glass unit can be used in their operable windows. See photos here:

    LiteZone Glass Inc. is in discussions with several other residential and commercial window and curtain wall manufacturers to offer LiteZone® IGU options with their framing systems.

    Using different thicknesses of glass units in the operable windows versus the fixed windows has not been an issue for our customers. Operable windows always look different because of screens and the extra framing members etc.

    LiteZone® insulating glass units installed in Fenstur Windows and Doors Ltd. fixed and operable wood windows and “lift and slide” wood door are featured in a video on Matt Risinger’s YouTube Channel here:

  12. Greg_Clarahan | | #30

    Major curtain wall companies have confirmed that for significant custom curtain wall projects they will increase the thermal break to accept thicker LiteZone® glass units
    • Will quote projects with LiteZone®
    • Can incorporate up to LiteZone® L0679 (4.4” thick) insulating glass
    – R17 centre of glass
    – R14 for a 4’ x 5’ vision area
    – Spandrel area can accommodate more insulation because of increase depth

    LiteZone® L0465 glass units can be used with existing Alumicor Series 2600 curtain wall systems and likely can also fit into other common curtain wall systems being used by glazing contractors in Canada and the USA.

  13. Greg_Clarahan | | #31

    For fixed windows, it is possible to install a LiteZone® glass unit directly into a wall opening without the cost of a traditional window frame. This must be detailed properly. See examples of details showing how to install a LiteZone® L0679 insulating glass unit (4.4” thick) directly into a wall opening without a traditional frame here:

    In addition to saving the cost of the frame, the LiteZone® “frameless” option eliminates energy losses that would occur through the frame. It also reduces risk of air and water infiltration by having only one connection (the IGU to the wall) instead of two (the IGU to the window frame and the window frame to wall). It can also achieve clean sightlines with an appealing, minimalistic design aesthetic.

    1. Deleted | | #35


  14. Greg_Clarahan | | #32

    LiteZone Glass Inc. only manufactures LiteZone® insulating glass. It does not manufacture windows or curtain walls. LiteZone® insulating glass is available for sale to home owners, commercial building owners, builders, renovators, glazing contractors, as well as window and curtain wall manufacturers, and to anyone else wishing to purchase truly high performance and long lasting insulating glass.

  15. rockies63 | | #33

    As to the exterior glass surfaces themselves, are there any advantages to using Cardinal glass or are they typically built with regular glass? Can the units be built using tempered glass for added security or for buildings in a wildfire zone?

    1. Expert Member
      BILL WICHERS | | #34

      Tempered glass is often required for larger windows, maybe even all windows now. Tempered glass is more for safety than security though. If you want extra security, laminated glass is a better choice, or wired glass (but that looks crappy on a residential project).


  16. tdh2106 | | #36

    Reviving this thread to see if anyone now has direct experience to share with LiteZone?

    In addition to buying direct and doing a frameless install, it looks like more window manufacturers are picking them up (e.g., I'm getting quoted by Aluprof with LiteZone IGU's). So, I'm thinking that there might now be someone out there that is willing to provide a candid review. Any takers? Looks pretty great on paper...

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