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cross section of pella fiberglass window material with callouts

Pella Fiberglass vs. Milgard 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 Milgard basic fiberglass to the test.

Won't Bend
On average, Pella fiberglass is

stronger than Milgard fiberglass in a bend test.75

Won't Break
On average, Pella fiberglass is

the tensile strength of Milgard fiberglass.76

Pella Fiberglass Defeats Milgard Basic Fiberglass

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.


3-point bend testing performance based on testing 7 samples of each material using ASTM D790 test methodology.

Deliberate Strength vs. Random Strength

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

a close view of pella's fiberglass material

Pella Impervia, our proprietary fiberglass

Our proprietary fiberglass is created through a one-of-a-kind manufacturing process. Starting first with an intricately woven mat that is strong in all directions, we add additional rovings, pultrude the materials, inject polymer resin and heat to create the strongest material for windows and patio doors.61

a close view of traditional fiberglass material

Milgard basic fiberglass

Conventional fiberglass, available on Ultra Series from Milgard is made of random glass fibers combined with resin. These materials are then pulled through dies to create fiberglass lineals.

Find the Right Product For Your Project

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

pella rep helping a window customer
Extreme Testing Brought to Life
Watch the Video


Hoisting a 3/4-ton pick-up in the air

For this extreme test, we hoisted 6,600 pounds into the air with just four Pella fiberglass window lineals. To demonstrate the tensile strength of our proprietary fiberglass, we attached the four lineals to the tow hooks and hitch of a pick-up truck with bolts, shackles and adapters. Then we attached the top of each to a forklift and suspended the truck into the air. This shows incredible strength and durability for your project.

testing material by hanging a pickup truck from a window frame
Hoisting a 3/4-ton pick-up in the air
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Concrete blocks bend test
woman with white blouse using the easy slide operator on a casement window

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

Learn more about Pella warranties