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Community and Q&A

Inline Fiberglass Windows

cbut8995 | Posted in General Questions on

Has anyone ever heard or used inline fiberglass windows?

I am stuck in between using fiberglass or uPVC windows? Which are better and which will last longer for NYC climate? I am building a new construction building as luxury rental and need something that will last years to come with tenants who neglect them. 

Thank you.

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  1. GBA Editor
    Kiley Jacques | | #1

    As you explore your options, consider the information provided in Scott Gibson's Q&A Spotlight: In Search of the Most Energy-Efficient Windows, where he covers Inline products.

    Regarding fiberglass vs. uPVC windows, Martin Holladay answered a similar question this way:

    First of all, the terms "uPVC window," "PVC window," and "vinyl window" are all interchangeable. When manufacturers brag that their windows are made of "uPVC," they are muddying the waters rather than clarifying the issue. All vinyl window manufacturers use similar vinyl. It's all the same stuff.

    Second, fiberglass window frames have several advantages over vinyl window frames.

    One advantage is that fiberglass has a lower coefficient of thermal expansion than vinyl. That means that these windows won't expand as much in the summer or contract as much in the winter. Moreover, the coefficient of thermal expansion of fiberglass closely matches that of window glass. That's a good thing.

    Other advantages: fiberglass isn't quite as soft as vinyl, and it may be more weather-resistant.

    Of course, fiberglass windows cost more than vinyl windows. If you can't afford fiberglass windows, vinyl windows will serve you well.

  2. alan72 | | #2

    Climate zone 5

    Northwest Detroit Suburbs

    We are still under construction on a new build. We installed Inline windows. So far, I’m very happy.

    Prior to ordering I drove to Toronto to see the product first hand and got a tour of the factory (no local showroom or distributor). They use cardinal glass and we spec’ed triple glazed windows. We have mostly fixed windows that have a nice low profile frame (no sash). We chose tilt/turn mechanisms for the operable windows- the sash is pretty wide on these. We chose regular sliders for the patio doors.

    We haven’t lived with them yet, but so far I’m happy.

    I’m happy to answer other questions.


    1. cbut8995 | | #3

      Do you have more pics of the windows close up? I am using Tilt and Turn windows on our whole building. Like your home, we are only using fixed windows and tilt and turn. How big of a difference is the frame size?

      1. alan72 | | #5

        I hope this helps.

    2. Expert Member
      BILL WICHERS | | #4

      Were you able to order direct from Inline and go pick them up? When I called them they pointed me to majic windows which has some kind of exclusive deal with them in the metro Detroit area.


      1. alan72 | | #6

        I worked directly with Inline.

        It was overall a positive experience - any negatives were really related to our home design (a lot of trapezoidal windows) and my impatience.

        They didn't send any one to measure on site - I needed to make an excel spreadsheet with all the trigonometry figured out to get the slope of the trapezoidal windows correct. Our framer and I did all the measuring.


  3. Sofiane | | #7

    We installed 8 triple pane windows (7 casement, 1 awning) and a patio door from Inline last year in our house in zone 6.

    In general, I'm very satisfied with the windows, especially with their performance. Most of them are in a sunroom and they made a massive difference in comfort. The only functional negative is that it can be a quite a bit harder to lock the windows if I compare them to our double pane pvc windows. They are easy to open and close though. I don't know whether this would apply to the tilt and turn windows. I believe they have a different locking mechanism.

    Another downside is that the fiberglass finish is quite easy to scratch, but that apparently is common to all fiberglass windows.

    I didn't order directly from Inline, so I can't comment on that part.

  4. rootsbuilder | | #8

    I don’t recommend Inline, poor construction and hardware, lousy customer service.

  5. YankeeJohn | | #9

    We chose Inline windows in 2017 for a whole house renovation in central Vermont because Inline fiberglass was one of a few windows rated for Zone 3 in Canada and our location gets fierce cold winds exposed on the side of a mountain. Inline was easy to work with and there were no problems with delivery or installation. We bought the windows directly from Inline. The windows performed well and the difference from our old Marvins was incredible. Unfortunately two of six double hung windows and two of three windows in a fixed mullioned window have a developed a seal failure and fog frequently. Two large patio doors and four tilt and turn windows from Inline continue to do well. Waiting for a response from Inline, will make a future post.

    1. egg2 | | #11

      Any update from Inline?

    2. Jemari | | #12

      Thank you for posting this. The kind of seal failure that causes fogging is the IGU (integrated glass unit) which Inline purchases from Cardinal. My understanding is the warranty on this compoenent of your windows is 10 years, and that duration is passed on directly from cardinal. The fogging failure is caused by the seal between the panes failing. Cardinal makes IGUs for a lot of different window manufacturers. Unfortunately the manufacturing flaw is likely with Cardinal, but the headach is for Inline. Regardless, it is important they handle it well and do right by you. Please let us know how Inline handled your IGU failure!

      1. oberon476 | | #13

        Might want to recheck your information, Inline uses cardinal glass but not cardinal IGU's (Insulating Glass Units).
        But you are correct that Cardinal does manufacture IGU's for many other companies,and Cardinal's warranty is 20 years.

        1. Jemari | | #14

          GTK. I spoke to the salesperson recently, but you know how techical discussions with salespeople go: they sometimes gloss over definitions or are unintentionally inprecise.

          1. oberon476 | | #15

            I also thought that they used Cardinal IG's, but their NFRC listing had been empty the last few times looked there so didn't know for sure.
            After reading your post I looked again and the listing is full. I checked under several different styles and different listings under each style and none of them were Cardinal IG units.

          2. Expert Member
            Akos | | #16

            I recently had a set of 8 Inline window IGUs fail. These were 10 year old south facing so a lot of sun exposure. The bottom warm edge seal discolored then cracked and eventually the IGUs all failed.

            There is no laser etching on the window or the seal, so I don't think these are made by a major glass supplier.

            I've been in touch with Inline, we will see how good their warrantee is.

      2. YankeeJohn | | #17

        Thank You egg2, Jemari, and Akos for posting about the ICU failures. I contacted the salesperson, Mark Bartolini, twice in 2022 who said in his email that he had forwarded my pictures and complaint to the service manager, and I received no response. We decided to live with the windows, but this year the third window of three fixed mullioned kitchen has fogged so that we can't look out of our kitchen window on many days. I plan to put my shoulder back into replacing our fogging windows. Can you advise me about what to expect from warranty service? Should I expect Inline to give me new replacement windows? THank you.

        1. egg2 | | #19

          @Akos and @YankeeJohn, have you heard anything from Inline?

          1. Expert Member
            Akos | | #20

            I got 7 out of the 8 replaced a couple of weeks ago (about 6month wait). I would put their service at 3/5 at best, took a number of emails and calls to move things along.

            I think part of the delay was that they had to have the IGU supplier look at the failed units. The IGU tech seemed to blame the seal failure to standing water under the IGU which was a bit strange to me. There was some small signs that water made it into the channel where the IGU sits but nothing I would consider major leak. All IGUs did fail on the bottom seal though (you can see separation bubbles between the caulk and the glass) so maybe their edge treatment there was not the best.

            For extra cost they did update the coatings for me, so that is one bonus to come out of this.

  6. user-2069108 | | #10

    We put Inline casement, awning and fixed windows in our Passive House in central Ohio.
    Our early research brought us to their Toronto facility, where we learned that all of the Canadian fiberglass window companies had Inline manufacture their framing materials.
    We dealt with them directly, and picked them up in TO. All of the paperwork was in order for the border crossing.
    The windows have performed perfectly (all but the south facing windows are currently covered with freezing rain, again). We have had no issues with the fiberglass scratching, or the paint scratching.
    Just make sure you give them actual size versus rough opening size when ordering. Don't ask how I know this ;-)

  7. Sofiane | | #18

    Since my last post, we’ve had one other lock break and replacement was a breeze. However, we’ve just had an IGU fail this week. Hopefully the warranty process won’t be too troublesome.

    I’ll post again once I have an update.

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