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cross section of pella fiberglass window material with callouts

Pella Fiberglass vs. Marvin Fiberglass

Intentional vs. Random, Which Strength Would You Prefer?

Your project deserve the best fiberglass window and door material. To see how we stack up against the competition, we put our exclusive fiberglass, developed using our one-of-a-kind manufacturing process for superior strength, and Marvin, basic randomly blown fiberglass, to the test.

Won't Bend
On average, Pella fiberglass has

the tensile strength of Marvin fiberglass.74

Won't Dent
On average, Pella fiberglass is

more impact resistant than Marvin Fiberglass.75

Won't Break
On average, Pella fiberglass is

stronger than Marvin fiberglass in a bend test.76

Pella Outperforms Marvin with Unmatched Strength and Lasting Durability

Pella's proprietary fiberglass material is the strongest material for windows and patio doors, engineered for lasting durability.61

As much as the competition in a bend test, which measures the flexural strength of a material by applying force via a single, concentrated load point in the middle.


Tensile testing performance based on testing 7 samples of each material using ASTM D638 test methodology.

The Strongest Fiberglass vs. Basic Fiberglass

Take a look behind the paint and see what materials make up Pella’s proprietary fiberglass and Marvin basic fiberglass.

a close view of pella's fiberglass material

Pella Impervia, made of our proprietary fiberglass

To meet Pella’s exceptionally high strength standards, our fiberglass starts with a proprietary structural mat. These strategically woven rovings and additional rovings are pultruded, or pulled through a machine, and heated with a polymer resin to create a thermoset material that won’t break down. Our fiberglass is the strongest material available for windows and patio doors.61

a close view of traditional fiberglass material

Marvin Ultrex, a basic fiberglass

Marvin’s Essential Collection windows and doors use randomly blown fiberglass rovings and heated with resin until the materials become one. The randomness of the fibers means it cannot withstand the incredible strength Pella Impervia fiberglass can.

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Work with a dedicated Pella representative every step of the way.

pella rep helping a window customer
Bringing Our Superior Strength to Life
Watch the Video


Withstanding a 10-pound bowling ball drop

To bring the strength of Pella fiberglass to life, we decided to take it to the extremes by dropping a 10-pound bowling ball from a height of seven feet onto a sliding patio door jamb lineal below. Whether it is a slipping hammer on the jobsite or even a bowling ball, our fiberglass is up to the challenge.

testing material by dropping a volleyball onto a piece of fiberglass material
Withstanding a 10-pound bowling ball drop
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woman with white blouse using the easy slide operator on a casement window
Get the Best Fiberglass Windows & Patio Doors

Designed to stand up to everyday wear and tear, Pella Impervia products offer an on-trend color palette, including black, and feature our latest innovation, the Easy Slide Operator window hardware, winner of Best in Show at the 2021 International Builders Show.

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Work with a dedicated Pella representative every step of the way.


Pella products are backed by some of the strongest warranties in the business.

Learn more about Pella warranties