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UPVC vs. fiberglass windows

b4316207 | Posted in Green Products and Materials on

Hello all. Building a new home in the Philadelphia area.

Looking for windows. Was considering fiberglass, but have been reading online that uPVC may be just as good but cheaper.

Can anyone comment on the pros and cons of each material?

Thank you.

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  1. GBA Editor
    Martin Holladay | | #1

    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. b4316207 | | #2

    OK thank you for your response , question what would be considered good quality vinyl windows , i have been reading that intus gets good reviews , but I would avoid not waiting 8-12 weeks to get them and was wondering if there is a US or Canadian manufacturer that is worth considering

  3. RyanLurie | | #3

    Hi Martin,

    I'm trying to research the differences between PVC and UPVC as I prepare to buy windows from Euroclime. I see that you've repeatedly said that there is no difference between the two. Can you point me towards some literature that supports your stance? Not because I doubt what you say, but rather because I'd like to have something other "Martin Holladay says..." when I talk to window reps and clients. Thanks!

  4. Trevor_Lambert | | #4

    The other downside to fibreglass windows is there are precious few (any?) truly high performance ones to choose from, from an energy standpoint. I know Alpen windows has some good numbers, but the jury seems to be out on whether the film they substitute for the third glass will stand up in the long term. At the very least, it's not comparing apples to apples.

    By the way, it was reported here a while back that Intus is no longer supplying windows for the residential market. I haven't seen any report of that changing.

  5. GBA Editor
    Martin Holladay | | #5

    UPVC stands for "unplasticized polyvinyl chloride."

    It is "unplasticized" because plasticizers haven't been added to the PVC. Plasticizers are chemicals added to make the PVC flexible. These plasticizers are used in products like shower curtains, sheet vinyl flooring, and children's toys -- never for windows. All vinyl window manufacturers use the same type of PVC (vinyl) for their windows. It is always unplasticized.

    For more information, see these web sites:

    PVC vs. uPVC

    Wikipedia: Polyvinyl chloride

    The following quote comes from the Wikipedia article linked to above:

    "PVC comes in two basic forms: rigid (sometimes abbreviated as RPVC) and flexible. The rigid form of PVC is used in construction for pipe and in profile applications such as doors and windows. It is also used in making bottles, non-food packaging, and cards (such as bank or membership cards). It can be made softer and more flexible by the addition of plasticizers, the most widely used being phthalates. In this form, it is also used in plumbing, electrical cable insulation, imitation leather, flooring, signage, phonograph records,[8] inflatable products, and many applications where it replaces rubber.[9] With cotton or linen, it is used to make canvas."

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