Misleading Claims About Fiberglass Windows

What Homeowners Should Know Before Comparing Infinity® by Marvin with Andersen Composite Alternatives

Homeowners comparing Infinity® by Marvin with Andersen composite windows may hear a number of claims about fiberglass that sound technical or concerning. In many cases, these claims are misleading, incomplete, or taken out of context in an effort to make Andersen Fibrex® composite products seem either superior or more comparable to Infinity by Marvin Ultrex® fiberglass.

These myths matter because they can distract from the more important comparison: Ultrex fiberglass is a strong, highly stable structural material, while Fibrex® composite is a wood-fiber and PVC/vinyl composite. That difference affects long-term strength, thermal stability, appearance, and window performance.

Below are some of the most common myths homeowners may hear and why the facts matter.

Misleading Claims About Finish and Maintenance

Myth: Infinity by Marvin fiberglass frames are like boat fiberglass and need to be waxed or refinished.

Reality: Ultrex fiberglass is not an exposed, boat-style fiberglass surface. Infinity by Marvin frames use a durable factory-applied finish designed for long-term window performance. Routine cleaning is appropriate, but waxing and refinishing are not required as part of routine maintenance.

Myth: Infinity by Marvin’s fiberglass finish is not durable, fades easily, and requires repainting.

Reality: Infinity by Marvin uses an extremely durable co-extruded acrylic capstock finish that is mechanically bonded to the Ultrex fiberglass frame. This finish is specifically engineered to resist fading, chalking, scratching, and chipping for years of maintenance-free performance, outperforming many conventional window finishes. It does not require repainting.

Misleading Claims About Fiberglass Strength and Stability

Myth: Fiberglass is brittle.

Reality: Ultrex fiberglass is engineered for superior structural integrity and is valued for its strength, rigidity, and durability. It is specifically designed to hold its shape and perform well in demanding exterior conditions.

Myth: Fibrex® composite is stronger than Ultrex® fiberglass.

Reality: Fibrex is a wood-fiber and PVC/vinyl composite. While it may be more stable than basic vinyl,  it is not the same as structural fiberglass. Ultrex fiberglass is the stronger and more stable frame material.

Myth: Fiberglass expands too much and is overly heat sensitive.

Reality: Ultrex fiberglass has exceptionally low thermal expansion, performing well in extreme heat because it is a stable thermoset material, unlike heat-sensitive thermoplastic (vinyl-based) frames. 

Myth: Infinity by Marvin fiberglass windows cannot handle home settling or foundation movement.

Reality: Home settling and foundational shifting is a structural condition, not a fiberglass or window problem. While extreme shifting can affect any window type, Ultrex fiberglass is strong and rigid, making it less likely than vinyl-based materials to flex, warp, or distort over time. 

Misleading Claims About Health and Warranty

Myth: Fiberglass windows off-gas.

Reality: Ultrex fiberglass is fully cured and stable. It is not a soft vinyl or plastic frame material associated with off-gassing concerns.

Myth: Infinity by Marvin does not warrant against argon gas issues, while Renewal by Andersen does.

Reality: This comparison is misleading. Neither warranty guarantees a specific percentage of argon gas will remain in the glass. The real comparison is protection against insulated glass or real seal failure – both Infinity by Marvin and Renewal by Andersen provide 20-year insulated glass coverage for this critical protection.
 

The Real Comparison Homeowners Should Focus On

Don’t let technical-sounding claims distract you from the essential difference: Structural Ultrex fiberglass vs. vinyl-containing Fibrex composite. Ultrex offers superior material strength, greater stability, and more durable long-term performance. For homeowners prioritizing strength, thermal stability, aesthetics, and lasting value, Infinity® by Marvin remains one of the strongest replacement window choices available.

Talk With Burnett About Infinity by Marvin® Windows

Choosing the right replacement windows can feel overwhelming, especially when different products sound similar. Burnett Home Improvement can walk you through the differences between fiberglass, composite, vinyl, and other window options so you can make a confident decision for your home.

Written by Neal Burnett for Burnett Home Improvement