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Inline Fiberglass Windows User Reviews

efficient_builder | Posted in Green Products and Materials on

I am interested to learn about other people’s experiences with inline fiberglass windows. I have seen a few comments here and there from Jonny_H, Reid Baldwin, Forrest Twombly, Sofiane Azzi, Alan Afsari and I would like to hear if they have any updates because I have had a less than great experience.

I learned about inline fiberglass windows from this website and went ahead and ordered 12 windows for a high-performance build in climate zone 6. (This site was an invaluable resource for sorting out all of the building science details). It was completed in summer 2019. There were 4 fixed windows, 6 casement, 1 inswing, and 1 tilt n turn door. To date I have had three window seals fail (two fixed and one casement) and one casement window locking mechanism fail. All of the casement windows are difficult to close and we are reluctant to open them because we don’t know if they will close again.

Watching the casement windows operate, they simply do not close all the way. On the locking side, the handle stops turning when the IGU still has ¼-1/2” to go. Then it’s up to the somewhat flimsy locking mechanism to pull the window in the rest of the way. There are clips on the non-locking side that match up to clips on the IGU- I am wondering if these are misaligned and not allowing the window to close all the way. When they were first installed, they were somewhat tough to lock, but nothing like now. I ran strings from opposite corners of the frame and those indicate the frame is planar. One very involved solution would be to shim out the nailing flange on the locking side of the window by ¼-1/2”. This presents some complexities with the top and bottom nailing flange as well as flashing, window returns, and trim (rabbet the trim?).

There is also a fiberglass ramp for supporting the IGU when closed, but it gets hung up on this- loud creaks and squeaks when opening and closing. I imagine this is stressing the IGU a bit each time and it’s another thing the locking mechanism has to fight. There are decent wear marks on the IGUs from the ramp. I did add some lithium grease to the ramp which did help.

Other issues that came up included telling me they couldn’t be shipped to my site after I had placed the order and not including NFRC labels which delayed the inspections. I am pushing nine months now trying to get this resolved with Inline, but I have nothing to show for it. Customer service leaves a bit to be desired. So, I am quite disappointed and frustrated and would like to hear how other people’s inline windows have been holding up and what their general experience has been. I am curious to know if this is an anomaly or not.

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  1. user-2310254 | | #1

    I don’t have any experience with Inline, but I wonder about the quality of your install. With your casements, it sounds like the window are not square and plumb in the openings. Not to discount possible manufacturing defects, but have you checked? Also… Sometimes this type of window needs to be adjusted after installation. I had to do this with one of my Andersen casements to correct a bit of “sag.”

  2. jonny_h | | #2

    My Inline order should be shipping within the next week or two -- I'll update my impressions once I have them installed! So far, I've been happy with my dealings with them.

  3. YankeeJohn | | #3

    I just posted about Inline windows in another string;

    Several of our windows have had the seals fail, they turned four years old this month, otherwise they have functioned well. Still waiting to hear from customer service. Post on this forum if you any advice re: customer service if you can.

    1. Expert Member
      BILL WICHERS | | #5

      That looks like a defective IGU. Inline uses Cardinal IGUs, or at least they did a year or two ago when I last spoke with people there. You might want to see if this is a warranty issue.


  4. efficient_builder | | #4

    Measured the diagonals and the frames are square. They are showing level. Strings from opposite corners are touching. We could nitpick on plumb, out ~1/8" over 4', but imagine they can handle that. The two other fixed windows have failed since the last post.

    I do have some service bulletins on lateral adjustments that mention binding. I will try this when it gets warmer.

    Pre-sale service was perfect and post-sale is the complete opposite.

    User-685535, I don't have any suggestions. My windows look the same with the fogging and getting a good bit of frost on the inside of the outer pane with the winter temps. They don't have the pieces bowing up like that though. Windows are 3.5 years old now based on install date.

    1. YankeeJohn | | #11

      Efficient Builder: There is a now second sash with the gray spacer material bowing up from the bottom. I contacted the Inline sales rep who sold us the windows who responded quickly and told me I would hear from the Service Manager at Inline. We haven't heard anything. Of 16 windows purchased in 2017 four have failed seals and fog in the center on cold days so you can't see through them on cold days. No problems with two large sliding doors and four 'Tilt and Turn', only a fixed window and the double hung.
      Are you going to live with the fogging and frosting on the cold days?

  5. dan_from_toronto | | #6

    I'm very close to order 13 windows from Inline and I'm trying to figure out if it's the right thing to do (fiberglass vs vinyl).
    I'm a bit worry and I consider the fiberglass a riskier option (based on what I read on the forums, which is not the best information but at least is more or less honest).
    I have a couple of reasons to choose fiberglass (stronger than the other materials, environmentally friendlier than vinyl, better design).

    If anybody can post their experience with Inline that would be great!
    Thanks a lot.

    This is what I found on a Canadian forum (this post is very old, from 2008)

    ""They are about 15% more expensive , but even thou their expansion rate is as close to wood as it gets they are potentially disaster waiting to happen. As opposed to vinyl windows, fibre glass windows are mechanically fastened on the corners of the frames. That means those window frames are screwed on the corners and over time with the contraction and expansion and a natural movement of your house joints will not be sealed anymore (I am not saying that this will happen for sure) where vinyl windows are welded 2gether on the corners, material is basically fused into one piece. so there is no danger of corners coming apart.
    Fibreglass windows are great for government projects especially like schools and hospitals, they have money to spend every 15 years or so."

    1. YankeeJohn | | #12

      As others have posted, excellent experience with sales and delivery. The windows made an immediate difference where we live in northern Vermont and the house was notably warmer. The 16 new Inline windows replaced 25 year old Marvin windows. Unfortunately the Inline have not held up. Year #3 we began to have failed seals that fog on the inside on cold days, and now two sashes that have some gray spacer material bowing up on the inside from the bottom. We have been in contact with Inline but have not had a response.

  6. AC200 | | #7

    Well, wood frame windows are glued and mechanically fastened, aluminum is mechanically fastened. Vinyl is welded (melted) together. Of all the window materials vinyl is the weakest and cheapest and has the worst coefficient of expansion.

    All of the windows have their place. Vinyl are the most economical but usually the shortest life span. Wood looks the best, but needs maintenance. Extruded aluminum clad wood solves that somewhat but they are very expensive. Aluminum has a very premium look with a very premium price tag. Fiberglass is a good combination of strength durability and cost.

    I don't put much stock in one post or two on the internet forums. Longer term history is a much better indicator. And I don't agree that internet forums are more or less honest. It really depends on who is posting and their motives. My brother has had Inline triple pane casements for about 15 years. One was sticky but after adjustment it was fine so that was an installation problem. One required a new mechanism but he opens his casements to 90 degrees open every day the weather allows which is a pretty heavy duty cycle.

  7. jberks | | #8

    I'm surprised you're finding negative posts about fiberglass. To that, I wouldnt be going off a post about fiberglass from 14 years ago.

    I opted for aluclad wood windows and I hate them. They're not garbage, but for the money I paid, they warp, they're a pain to operate, they're not energy efficient. The interior looks poor because it's painted wood. The exterior looks greater though, I'll give it that.

    All the windows I recommend now are inline fiberglass. They're the most cost competitive in Toronto, they look fantastic inside and out. They operate alright (same BS crank like any other casement, I wish they would offer a cam lock manual swing). Fiberglass is way more durable than vinyl, and wood. It doesn't warp from humidity issues, it's doesn't dent from abuse, it doesn't easily get fingerprints on the interior (fiberglass is inherently coloured, vs painted wood), you can do some pretty modern stuff with them and easily get triple pane vs some vinyl manufacturers balk at triple pane because they can't handle the extra weight.

    Everyone I know that got inline fiberglass, really enjoy them. I wish I had got them at the time I was specifying windows on my last build.

    Just My 2 cents

    1. AC200 | | #9

      "I wish they would offer a cam lock manual swing" They do have an inswing casement hopper. Series 700

      I don't think they look that great, more like a basement window. It's one of their more economical options.

      "(fiberglass is inherently coloured, vs painted wood)" That's not totally correct. Fiberglass pultrusions are a dull white, at least the ones I saw being made at the Inline factory, and need to be painted.

      1. jberks | | #10

        I stand corrected.

        I still think they look much better than wood and vinyl frames. I was just playing with some meet installed black inline windows a few weeks ago.

  8. YankeeJohn | | #13

    Would be interested to know if anyone has had contact with Inline Service regarding replacement of failed IGUs.

  9. dan_from_toronto | | #14

    I finally had installed all the windows at my house, Inline fiberglass. They look really great since I wanted those thin looking frames and the biggest possible glass surface.
    Now, since the steel doors prices went crazy I'm contemplating a fiberglass door, the door is roughly 1500-2000 CAD more than the steel one, the frame is thin and nice but I'm wondering if it offers the same level of insulation as the metal ones.
    I attach here a fiberglass door and a metal one. One of the image shows a photoshop exercise to see how it will look like

  10. dan_from_toronto | | #15

    What worries me is the quality of this fiberglass door in the long term. Their warranty for the frame is 10 years, other steel door manufactuers has 20 years warranty.

    Also here's a quote from a canadian forum by a competent door and windows installer.
    What do you guys think ?

    "The "wish" [pictures are a no go and I would be amazed if they were actually real doors. Take a look at the bottom rails, there is absolutely no strength there period. This door would twist and fail within weeks.

    Onto the next thing the insulation factor. For a start, steel and fibreglass share the same U-factor ratings for full, 3/4 half glass units and sidelights. There is no difference. You get NO increased insulation from a fibreglass door whatsoever.
    Then let's look at "why you should spend more on fibreglass. "Because it doesn't dent." That's about it. But it does chip and scratch and warp. As a matter of fact, most door manufacturers still insist on a multipoint lock system on a fibreglass door specifically because it warps. Then you have the "acceptable warpage" factor before replacement under warranty. That number is twice for fibreglass over steel.

    But even after all that, you missed the simplest check. What is the warranty on their doors compared to the rest of the industry? Well, it's half.

    So why is fibreglass pushed? Cheaper to transport, lighter, and fewer accidents in the plant. easier to cut and shape. No chance of water damage on unfinished products. When 1st introduced they were hand stained a tedious 3-day process and now it's a spray-on finish whether wood grained or solid.

    If you want a fibreglass door I will sell you one and thank you as will my bank account. Are you getting a superior product? Not in my opinion"

  11. Sofiane | | #16


    Only saw your post now. There should be a way to contact GBA members directly.

    We just had a second locking mecanism fail a few weeks ago. That was the second one in 5 years. Unfortunately, one of our IGU’s failed this weekend, which is a bigger concern. It’s the first one of our 9 windows.

    Our locks were replaced in record speed, I can’t wait to see how it goes for the IGU. The caveat is the warranty and warranty service are a bit different in Quebec, so I don’t know that my experience will correlate with others. For some parts of the window, like the frame, the warranties are the same. For the IGU, I actually have much shorter included coverage - 10 instead of 20 years, but service is usually through a smaller distributor which leads to a what is usually very responsive and useful customer service.

    At any rate, I’ll keep you posted.

  12. jollygreenshortguy | | #17

    This was a fascinating comment string to read.
    I live in an old house with single pane divided light casement windows. The frames were made from locally grown chestnut in 1903. They're all still in perfect working order with no hint of deterioration.
    Once a year the local vinyl window salesperson knocks on my door and I politely tell him to go fly a kite.
    I do want to look into some kind of easily removable storm sash because for about 3 months of the year it's cold enough that it would make a noticeable difference.
    In 3-4 years I anticipate building my own house. If I can track down lumber of similar quality I'm considering making my own window frames, identical except a bit thicker to allow for double glazing.

    Does anybody know of a manufacturer that gives a 120 year warranty?

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