Fiberglass Windows
Fiberglass windows are one of the more popular window frame materials (behind vinyl windows, which account for some 70% of all windows sold today). Interestingly, fiberglass is very difficult to distinguish visually from vinyl windows. However fiberglass is a more durable and more sustainable product that will typically have the same basic performance numbers as a comparable vinyl window (at a much higher overall cost). Let’s delve into fiberglass window pros and cons, cost considerations, recommended brands and series, as well as homeowner questions and answers.
Review By John M. - Site Editor Publish Date: March 6, 2016
Last Update: November 14, 2025
Fiberglass windows have a lot going for them. They’re strong, nice looking, durable, achieve pretty darn good energy efficiency ratings (that last a long time) and can be painted (unlike vinyl). Truthfully, I don’t think it’s a big deal that they can be painted, but I know it is to certain homeowners.
Fiberglass Windows Pros And Cons
In terms of cons, this frame material has only one real downside - what fiberglass windows cost. They are often 40% to 50% more than vinyl window costs. Plus, their energy efficiency numbers are more or less the same as vinyl. (Honestly, this is a bit of a gray area that is worthy of a full article, but there is a lot of data that suggests these two materials are similar in terms of their overall performance.
As I stated earlier, fiberglass windows are often 40% to 50% more expensive than vinyl. So while vinyl windows might run $400 to $1200 installed, fiberglass might run $1200 to $2400 installed (or higher in certain cases with upgrades or installation requriements).
Fiberglass Window Costs
Please note that there aren’t many budget fiberglass window manufacturers, which is why the cost starts at $1200 instead for the $800 for vinyl windows. This is a significant increase in cost and is often times the reason that so many less consumers opt for fiberglass vs vinyl windows.
These are some of the our recommended brands and options for fiberglass windows. Note that there are far fewer recommendations than with vinyl windows.
Recommended Brands
Alpen HPP Zenith and Tyrol Windows And Doors. Both of these series are super high quality fiberglass products that achieve amazing performance numbers. While Alpen HPP (headquartered in Colorado) might be tough to find in your zip code, if they are, this is one of the absolute best brands out there.
Marvin Elevate, Essential, and Modern Series. Marvin Windows is probably the best known fiberglass window manufacturer and they don’t disappoint. All three of these series are very well made, quite nice looking, and achieve impressive performance numbers.
Inline Fiberglass Windows. While based in Canada, Inline sells through reps to a handful of northern states in the U.S. Very well made and constructed, you can expect performance and good looks.
Milgard Ultra. The Ultra is a nice fiberglass window. While not in the same class as the first three brands, the Ultra is nonetheless a nice fiberglass window that won’t break the bank.
Pella Impervia. I’m going to include this series because many American consumers know it. However, I’m not the biggest fan — I think the four brands and eight series mention before the Impervia is the better bet. Just my opinion.
Thanks for visiting our questions and answers section. Below are homeowner reviews, price quotes, material comparisons and lots more related to fiberglass windows. As always, we're happy to field your questions or post your review. If that's your intent, please use the email link toward the top of this page. Cheers.
John, any reason that you don't list the Coastal series by Marvin?
Hal, Marvin makes excellent fiberglass windows! I did not know that was available in Hawaii, so thank you for that. Bottom line on Marvin is if you can afford it, it's an excellent option. I would still love to know how the price point compares to the Anlin Ali'i Extreme. Do let me know what you find as my understanding of Hawaii is very limited.
Fiberglass Windows Reviews
Review By John M. - Site Editor
Marvin Coastal
Hal - Homeowner - November, 2025
Website Editor's Answer
Editor John M. - November, 2025
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