Fibrex vs Fiberglass | Compare These Window Frame Materials

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Fibrex vs Fiberglass Windows

Fibrex vs Fiberglass

Fibrex vs Fiberglass let's compare and contrast how these two popular window frame materials on strength, aesthetics, energy efficiency, and on cost.

Fibrex Cost: $$$$

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What Is Fibrex?

Fibrex is a proprietary name that the Anderson corporation and their franchise Renewal By Anderson uses as the main component of their window frames. I should say that Anderson also uses fibrex in their 100 series composite window that you will find in every Home Depot across the United States.

Fibrex is a mix of roughly 60% vinyl and 40% wood or wood shavings or sawdust (not quite sure the consistency when it goes in, but you get the picture). I give those percentage breakdowns, but the real breakdown is proprietary, so take my percentages with a grain of salt. The result of mixing the vinyl and wood particles when creating their extrusions, at least according to Anderson, is a window frame that is twice as stronger as vinyl.

By combining these two different materials in the window manufacturing process is why it is considered a composite window frame.

What Is Fiberglass?

Fiberglass is decidedly not a proprietary name as it is used to make thousands of products in myriad industries. From a material point of view, fiberglass is simply plastic that is reinforced with glass fibers. Fiberglass is one of the materials used to make window frames. Popular fiberglass manufactures include Marvin, Alpen, Inline, Milgard, Fiberframe, etc. (the list goes on and on).

"Even though fiberglass is a combination of two different materials in the window manufacturing process, it is NOT considered a composite window frame. It just goes by fiberglass and is its own frame category."

Fibrex vs Fiberglass : Strength

How do these two materials compare to one another in terms of strength? According to Marvin (one of the biggest names in the fiberglass world), their Ultrex fiberglass is three times as strong as Fibrex. But it depends on what type of test we are talking about. Marvin relies on the masure of flexural modulus, which is the ratio of stress to strain. How important is this measure? It turns out, not all that much.

Here's why the overall strength between fibrex vs fiberglass doesn't matter. Both composite and fiberglass are two of the strongest materials on the market. In 99% of all residential projects, these two materials are plenty strong for residential homes. Why? Windows are not load bearing - they are placed inside a wood frame, which may or may not be load bearing. The window only has to support its own weight, which it can do many times over.

It should be said here that neither fibrex nor fiberglass are as strong as aluminum windows. Aluminum windows are by far the strongest window material on the market. It is the reason that aluminum windows are required for all commercial buildings and developments. (Aluminum gets horrible energy efficiency numbers so that's the big disadvantage.) But going back to my main point of fibrex vs fiberglass, these are both strong materials.

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Fibrex vs Fiberglass : Aesthetics

How do these two match up in terms of aesthetics? Because aesthetics is based on personal taste, I feel like this is really in the eyes of the beholder. In my opinion, however, fibrex tends to be the better looking window frame over fiberglass. To me, fiberglass windows look very similar to vinyl, although fiberglass can be painted. Fibrex makes for a very good looking window that has a similar look to a wood window with a finish. I think a lot of consumers would probably agree that the fibrex is the better aesthetic over the fiberglass, but then again, Marvin makes one of the nice looking windows out there.

Fibrex vs Fiberglass : Energy Efficiency

Comparing these two materials on energy efficiency is a tough one. Very close. Fiberglass is slightly more energy efficient over fibrex. Here again, the point is kind of moot because there are so many factors that go into making a window unit that is energy efficient. Look at the air infiltration rating of a particular window to find out whether it is a good performer or not. The Renewal By Andersen window is for instance not very impressive when it comes to AI rating.

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Fibrex vs Fiberglass : Cost Comparison

Both of these materials tend to be expensive, certainly more so than vinyl. While Renewal prices are quite high, the Andersen 100 series through Home Depot tends to be relatively well priced. The Milgard Ultra fiberglass window is going to cost less than a Renewal, while a Marvin Elevate should run somewhat similar or a bit more expensive than a Renewal. Prices are all over the board in general so it's almost impossible to say which material is more costly. It's on a case by case basis.

Fiberglass Cost: $$$$

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