Ultrex FiberGlass


Fiberglass has an amazing strength-to-weight ratio, which is one of the reasons why it’s the material of choice for boats, bridges, guardrails, ladders, and hardhats. It’s also highly durable, doesn’t leak, corrode, or rot, and unlike vinyl and non-fiberglass vinyl/wood composites like Fibrex®, Ultrex is extremely stable.

The Ultrex Fiberglass Difference

Ultrex is a pultruded fiberglass made by combining thin strands of strong glass cables and saturating them with compounded resins. This material innovation has nearly 25 years of proven performance.

Marvin didn’t join the fiberglass window and door industry— Marvin pioneered it!

Ultrex Fiberglass can be found in Marvin Elevate, Marvin Essential and Infinity from Marvin


Ultrex pultruded fiberglass has a tensile strength 8x stronger than vinyl and 3x stronger than non-fiberglass vinyl/wood composites like Fibrex®. Windows and doors made with Ultrex® bend and flex less, resist cracking and separating, and stand up better to everyday wear and tear.

Impact Resistant

Ultrex fiberglass is 3x more resistant to impacts than non-fiberglass composites and can withstand impact from wind-blown debris, branches, rain, hail, and even a direct hit from a baseball.

Ultrex expands 87% less than vinyl and 75% less than Fibrex®. Windows and doors made with unstable materials can soften and sag in high temperatures and are more prone to leaky seals, a loss of structural integrity, and poor operation. Ultrex expands at virtually the same rate as glass which ensures long-term performance and improves energy efficiency.


Our proprietary, mechanically bonded, acrylic finish is up to 3x thicker than competitive painted finishes. Ultrex stands up to harsh UV rays, resisting chalking and fading in even the darkest colors.

Energy Efficiency

Ultrex is 500 times less conductive than roll-form aluminum, so homes retain more heat in the winter and stay cooler in the summer, which translates to lower energy bills.

Jobsite Ruggedness

When installing windows and doors made with strong and stable Ultrex fiberglass, you can expect a consistent installation, and there will be no need to worry about less-than-perfect alignment or long- term performance issues.