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I have narrowed my search for fiberglass triple-glazed windows to Fibertec and Thermotech — seeking comments about these two

JoeUSAF | Posted in Energy Efficiency and Durability on

I am building an Energy Star certified home with fiberglass, triple glazed, low e casement windows and slider/patio doors in Connecticut. I prefer using a Canadian company because of their expertise with fiberglass, triple glazed windows and sliders. I must have window specifications for the Energy Star certification, preferably NFRC ratings or at least independent U, SHGC and VT value ratings. Window ratings do not seem to be diificult to acquire but slider/patio door ratings can not be provided by some manufactures for fiberglass triple glazed sliders and French doors.

I have narrowed my search to two Canadian companies, Fibertec and Thermotech, who can furnish me with this data if not NFRC. Does anyone have any experience or recommendations about these two companies? Also, can anyone recommend European companies who are cost competiitive with the Canadians and can furnish this data? Thank You.

Joe in CT

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  1. user-757117 | | #1

    I know that Thermotech has received some not-so-favorable commentary about their customer service...
    But my own experience in dealing with Thermotech has been positive.

    The windows I ordered were a delivered a little late but not rediculously so...
    And every time I contacted them I received prompt service.

  2. dankolbert | | #2

    I am among the legions who have had less than positive experiences with Thermotech - minor warranty issues that have dragged on for literally years.

    Have you looked into Intus? Contact Maine Green Building Supply - I believe their distribution area covers CT.

  3. user-1110235 | | #3

    I found the Internorm ThermoPassiv to be very competitively priced within $1000 of the Thermotech quote for the whole home, and we are more than thrilled with both the performance (Certified Passive house components), and the service we received from the company NorthWin ( who brought them in for us. has been top notch! you can see pictures of the windows installed at

  4. jinmtvt | | #4

    Unfortunately i've had bad experience with one of those.
    and when i mean BAD ..i mean like in multiple minor defects + majors defects on every windows.
    I will have to say, consider something else.

    I have had recent discussion with dr Guido Wimmers from Northwin in BC,
    he seems like a serious person and one of his casement i believe , just received PH certificate.
    Don't know the pricing details, but i would give him a call .
    778 317 0035 i believe.

    good luck!

  5. user-1115477 | | #5

    Have you considered Accurate Dorwin (Canadian) for fiberglass ? If so, what is your assessment of them? I had some (relatively) minor problems with them, but pretty good, overall.

  6. user-1012653 | | #6

    When I was looking I got numbers from Thermotech, Accurate, Intus, Fibertec, Inline, Serious, and a few other US ones (Integrity, Pella, Marvin, and Kolbe).
    Out of all of the fiberglass Canadian ones, Inline was the one I was going to go with. They had the best pricing, great service. Accurate was also very helpful. Intus had good pricing too, but they are uPVC so I was not interested. Thermotech was by far the highest price, just under double Inline price.
    However I ended up going with Kolbe and Kolbe. Their 1 3/8 triple pane windows look great with good ratings. We really wanted a wood interior and black exterior. We went with the Ultra EP line. It is a wood clad however, not fiberglass (thick extruded) The fixed windows u are .19 and the casements are .21. They can do any class package the fiberglass guys can. Price wise they were the same as Inline. We just took delivery last week and have been installing them. So far I have been very impressed with the quality, fit and finish. They are beautiful.

  7. jinmtvt | | #7

    Not to push it to hard, but why are u looking specifically for fiberglass framed windows ??

    I personally made that choice based on energy efficiency rates and marketing hype.
    I wouldn't go with fiberglass as first choice if given options anymore.

    First off, premium quality uPVC windows offer very similar energy efficiency, some also have the option of aluminium covers which is what i'd use for exterior.
    Then with pvc the corners are welded, makes for a very strong window with curren technologies,
    with fiberglass ( at least all of the canadian's manuf ) the corners are fitted with a plastic insert,
    glued and sealed with foam.

    It is not that bad from a sealing standpoint, thought it will never catch up with welded corners,
    the problem is that it is not rigid at all .

    Then the fiberglass pultrusions have pretty large tolerances, some lengths have "twists" and angles on them, similar to how a 2X4 twists on itself, which makes perfect alignement near impossible.

    Then , even if the surface is very well painted, it chips off very very easily.
    There are always some paint defects in corners from fittings and rubbing the stops.
    Very hard to get a perfect finished products, and at the price we pay for windows ....

    I stumbled upon a very badly handed batch, with many defects and no QC at all ... this biases my opinion some, but the facts are that fiberglass being what it is, it is still a very fragile product with near impossible perfect finish.

    Aslo it resists scratches and dents extremely poorly,
    i have young children and their play room is set up in the living room for now,
    many large windows, low height + large inside bottom plate = full of toys = full of scratches :p
    white pvc while not as beautifull, woul'dve handled that much better i am sure.

    Don't want to sound anti-fiberglass at all, not my point.
    If ( and if ) they really meet their energy figures on real delivered windows,
    and if the corner/finish issues are better than from my experience
    ( could possibly be with all other manuf, i only have a single experience )
    then i'd say why not.

    Still, i will consider PVC and german aluminium windows for all of my future projects.
    From my standpoint, windows are supposed to last 50 years +
    ( not glazings, but theese can easily be replaced )
    talking about framing components ...

    not sure that FG has what it takes to go through time.

    my 2 cents

  8. jinmtvt | | #8

    Also please don't drool on the hyper low U values of the windows,
    the energy difference between a 0.2 and 0.15 total window product is marginal at best
    from a residential standpoint ( unless ur house has 50% of walls in windows :p )

    Getting the best possible glazings , choosing correct SHG control depending on orientation
    and total quality of product is far more important.

    I choosed a specific because of the advertised U value, will not make that mistake again.

    Windows are expensive, and need consideration of ALL factors, not only performance.
    Just like purchasing a car ...

  9. user-968917 | | #9


    Did you ever look into Duxton Windows and Doors? They also make a great product, can provide multiple glazing manufacturer options, and I have used them a number of times. They are based in Winnipeg, Manitoba.

  10. sunstone | | #10

    In Toronto here I tried triple glazed 'Ostaco' windows. They claim to be trying to get EE.
    Vinyl frames but with insulated cavities to give thermal break, triple pointed locking casement system.
    The windows came with different specs than quoted by the engineer by phone when I talked to investigate. Are these significant changes?
    U-.17 went to.95, VT.39 went to.43
    (SHGC is .26, air leakage is .162, Energy Rating of 34, low -E coating, argon filled and the engineer quoted Cardinal272 Lo-E glass with XL spacers.
    That said (as Jin points out) I love my unit. It is in a north wall, 2nd floor over a busy street and keeps the sound out very well and temperatures at the glazing are 1-2 degrees less than room. I built a very insulated 'buck' to hold it

  11. sunstone | | #11

    In Toronto here I tried triple glazed 'Ostaco' windows. They claim to be trying to get EE.
    Vinyl frames but with insulated cavities to give thermal break, triple pointed locking casement system.
    The windows came with different specs than quoted by the engineer by phone when I talked to investigate. Are these significant changes?
    U-.17 went to.95, VT.39 went to.43
    (SHGC is .26, air leakage is .162, Energy Rating of 34, low -E coating, argon filled and the engineer quoted Cardinal272 Lo-E glass with XL spacers.
    That said (as Jin points out) I love my unit. It is in a north wall, 2nd floor over a busy street and keeps the sound out very well and temperatures at the glazing are 1-2 degrees less than room. I built a very insulated 'buck' to hold it

  12. sunstone | | #12

    In Cranbrook B.C. on a project we used Innotech Windows
    Fantastic specs, quality control, customer service etc... They are making a European 'tilt and turn ' window that surpasses anything I have seen. I wouldn't be surprised if they are the best in North America. Check them out

  13. JoeUSAF | | #13

    Gentlemen, Thank you all for your insights on windows. If cost effective, I have been leaning towards fiberglass over aluminum clad wood or PVC for several reasons, #1. Fiberglass expands and contracts at the same rate as glass. For those companies which use all fiberglass components in their windows, I believe this factor will prevent the leakage failure of the argon which may occur over the long run. Accurate Dorwin, Fibertec, and Thermotech all use fiberglass only components while some other companies use PVC internally in their fiberglass windows. #2. Fiberglass will not rot. #3 Exceptional U, SHGC and VT values. #4 I do not beleive that an internal, clear, synthetic, polyner film can adequately substitute for glass in triple glazed windows and challenge those manufacturers to prove it has long range durability and visibility. when compared to glass. I believe Accurate Dorwin makes an excellent fiberglass triple glazed window, but the only problem i have with them is that they can not supply me independently tested U, SHGC, and VT values for their sliders/patio doors. This data is essential for my Energy Star Hers Rater when he inspects my new home and certifies it as an U.S.EPA Energy Star home.

  14. jinmtvt | | #14

    If i may,

    #1 i am not sure how framing material and its thermal expansion is related to retention of argon within the IGU ... i do not think it is related, would seem like the IGU itself is responsible for the sealing of its internal, and if the window manufs. follow the IGU's spec for installation ... anyone could chime in on this ?

    #2 pvc and alum also will not rot.
    #3 that is up to the IGU, most fiberglass manuf now offer top notch IGU of course, as may any other window manuf.

    #4 triple glazed is the minium ...2013 .. only consider triple glazed , argon filled and suitable arrangement of low e films

    i was told that there was a difference of approx 10% in total window prices from double pane to triple pane IGU in 2008 . is it still similar ? if so , glazings = 20years + lifetime with recent standards
    should pay for itsef and still get the additional comfort as a bonus :)

    Please again i am not trying to grudge against fiberglass windows, my experience is limited to 1 manufacturer, but top QC and innovative construction methods is a mustm thus i believe that FG framed windows are more prone to quality problems than top notch PVC units.

    if possible, pay a visit at the factory before purchasing !

  15. Matthew Salkeld | | #15

    Hi Joseph,

    I am the Eastern Ontario rep for Fibertec. I would be glad to answer any questions about our windows at 613 606 1546. Another consideration is condensation resistance. CR is unrelated to U value, it is a thermal bridging issue. Our windows CR range from 60 to 70 on a scale of 1 to 100. We sometimes hear that triple glazed vinyl windows quotes come in higher than ours. Our windows use a closed tube frame, whereas all other brands of fiberglass use an open back (a cross section of frame looks like this ], ours look like this []) so it is torsional much stronger. We produce fixed windows up to 60 square feet in area, around double the size possbile with an inherently weak vinyl frame.

    Vinyl frames are very bulky looking and PVC is extraordinarily toxic for those who manufacture it. It produces dioxin, a potent carcinogen, when it burns or smolders. Turns out this is a serious issue for firefighters.

    Our windows carry a lifetime warranty on the frames and 20 years on the IG, both warranties are transferrable. Our glass stops and mullions are made of fiberglass unlike competitors who use vinyl for these components. We fabricate the IGs in our own factory. This improves quality control and delivery time.

    While you can't trust my advice on Thermotech, I will say they have a poor rating with the BBB and their prices are the highest.


    Matthew Salkeld, P.Eng.
    Fibertec Windows and Doors

  16. Matthew Salkeld | | #16


    Please note we have published data from NFRC on U, SHGC, VT, CR and centre-of glass values. We use Super Spacer, a silicon foam spacer, that as far as I know has the higher R value and has been in use for decades. All our windows are Energy Star labelled.


  17. JoeUSAF | | #17


    Thank you for the info on Fibertec. I am interested in your fiberglass triple glazed low e windows and slider/ patio doors. I have sent your representative, Mr. Hall, my new house plans and an email explaining them, so that he can provide me with a quote/estimate. I also asked him to provide me with some former customer references in New England so that I may call them. Thank You for providing your phone number so that my contractor and I may contact you about any further questions which we may have.


  18. JustHousing | | #18

    I have had both brands installed in buildings I designed and have been pleased with both products. Customer service was more problematic with Thermotech, but I am in Minnesota and very far from Ottowa. The windows are virtually the same product, I believe both use Inline lineals and the glass options are similar. My contractors' responses would favor Fibertec in terms of service from the distributor.

  19. mrgregpittman | | #19

    I got multiple quotes when I remodeled our entire house and wanted to install replacement windows, entry door, and siding. I don’t know about Fibertec, but I’ve heard Thermotech have good replacement windows and doors. You can look up their business reviews and ratings on BBB (Better Business Bureau) to get a better idea.

  20. cabbagepatch | | #20

    Mathew Salkeld

    I believe that you are purposely misleading people on this forum. Your comments of other competitors products is particularly troublesome. You mention that other manufacturers use vinyl mullions, I am challenging you to provide the name of the company/companies.

    Furthermore as you mentioned that Fibertec manufactures their owned sealed units. May I also ask who is the governing body who Fibertec is certified through. I have not found Fibertec certified by any including IGMAC who are the most well known. Therefore if you are not certified, you are not permitted to state performance ratings nor attach any NFRC, Energy Star or AAMA stickers making your performance claims simply fictitious. It would be considered fraud otherwise.

    I look forward to your prompt response to both of my questions.

    Btw your closed back profiles prevent you from achieving lower(better) U values than an open back framed window....

  21. jinmtvt | | #21

    I have found Fibertec on NFRC.
    Are you referring to IGU units only mr Johnson ??

  22. cabbagepatch | | #22


    As part of the NFRC Product Certification Program insulating glass units used in NFRC certified and labeled products must be certified as meeting certain performance requirements by a third party IG certification program ("IGC Program(s)”) listed by NFRC in the directory prior to those products obtaining NFRC certification authorization.

    There are five Insulating Glass Certification Programs the manufacturer could participate in as found in the IGC Directory. I have not found FIbertec in any of the directories. Therefore manufacturers are required to cease labeling until full certification can be met or alternatively be removed from the NFRC program.

    Therefore I am asking who is certifying their IGU's, yes.

    Here is the directory.

  23. Casshua | | #23

    Hi all,
    In reference to B Johnson's statement about Fibertec - the NFRC website hasn't been properly updated for years. Fibertec IS certified by the NFRC and does make their own sealed units.

    It's a high quality product with a lifetime warranty.

  24. cabbagepatch | | #24


    Thank you for the informative response. However you did not answer the question and totally missed the point entirely.

    As you are the second person to state this, I acknowledge that Fibertec makes their own sealed units. As the NFRC governs the way windows are rated/certified, there are 5 governing bodies that certify the sealed units that go into these certified windows . If you do not certify your units, you are not permitted or allowed to publish or state thermal performances and refer to them as certified. The NFRC will not certify the window with glass option and therefore you are not allowed to print NFRC or Energy Star stickers and place them on the windows. You may refer to your windows as non-certified/non rated windows and sell them as such.

    Therefore who does the certification for the Fibertec sealed units? Who is the governing body that certifies Fibertec's seal unit production? Please refer to the link I have provided above in my earlier post. As Mr. Salkeld did not respond nor did you answer my question. However I would like to give you the benefit to clarify this for everyone.

    Thank you.

  25. GBA Editor
    Martin Holladay | | #25
  26. cabbagepatch | | #26


    Thank you fore the response. Unfortunately you do not understand as well. When Fibertec registered those window and options, they were not manufacturing their own units. They were purchasing them outside from a third party. But it was from a certified third party IG manufacturer. Now they manufacture their own units and FIBERTEC is not on the list of certified IG manufacturers. Therefore they cannot LABEL their product LEGALLY with the glass they manufacture. They can label if they use a glass manufacturer that is certified but they do not.

    The IG certification is to ensure that companies all abide by the same rules and the IG are manufactured and tested to the same standard.

    If you still do not understand, call any window company to explain. Or the list of certification companies I provided on the link. Please reread my earlier posts.

    That is why I am asking who certified them. They are not on the list.

  27. jinmtvt | | #27

    Fibertec used to purchase their glazings from CLO i believe,
    which filed for bankruptcy in 2010 ??
    They probably started making their own IG since then ??

  28. ramzak50 | | #28

    Aren't there any decently rated window manufacturers of triple pane fiberglass windows close to us in Oregon?

  29. user-4435615 | | #29

    Try Alpen High Performance Windows out of Longmont, CO. All the specs are on their web site. I'm opting for their (NFRC Label): R-7.1 (U-.14), SHGC-.27, VT-0.44, CRF-67 [Center of Glass = R-14] triple pane windows. They do have some higher performing Quad pane and some lesser performing windows. There are all kinds of variations on SHGC and VT with expected changes in the U-factor.

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