Understanding the Andersen 100 Series, Renewal by Andersen, Fibrex® Composite, and Ultrex® Fiberglass

Homeowners often compare Infinity® by Marvin and Andersen windows as though they are similar products, but the comparison can be misleading for two important reasons. First, Andersen offers two very different composite window lines: the Andersen 100 Series and Renewal by Andersen. Second, both Andersen products use Fibrex® composite, while Infinity by Marvin uses Ultrex® fiberglass, a fundamentally different frame material category. 

These distinctions are important and compare more than just brand names. It is a difference of frame material, product tier, sales model, warranty, installation quality, and long-term value.

Comparison Overview

Before looking at the details, here is a simple way to think about the three options:

The Four Things That Determine Window Quality

A window’s long-term performance depends on four main factors:

1. Frame material
2. Glass package
3. Component quality
4. Installation quality

All four matter, but frame material is one of the biggest differentiators in both appearance and long-term performance. It affects appearance, frame thickness, glass area, structural stability, thermal expansion, seal durability, air infiltration, and how well the window functions over time. 

Frame Material: Why Infinity Fiberglass Stands Out

The best window isn’t just the one with the most recognizable name or the highest price. It is the one that offers the strongest combination of beauty, comfort, durability, and long-term value.

Infinity by Marvin windows use Ultrex fiberglass, a pultruded fiberglass material engineered for exceptional strength and stability. The Andersen 100 Series and Renewal by Andersen use Fibrex composite, which is made from wood fiber combined with PVC/vinyl.

Because of this material difference, Infinity by Marvin offers several important advantages:

• Narrower frames for more glass area, better views, and a cleaner appearance
• Greater structural strength and stability through temperature changes
• Better support for long-term seal performance and smooth operation
• Premium replacement-window quality backed by a stronger overall warranty

Fibrex composite may be an improvement over basic vinyl in some areas, but Ultrex fiberglass remains the stronger and more stable structural material. That difference influences the entire window system, from appearance and glass area to long-term stability and performance.

Simple takeaway:

Ultrex fiberglass behaves like a structural material.
Fibrex composite behaves more like a vinyl-based material.

Aesthetics & Curb Appeal: More Glass, More Light, Cleaner Appearance

Stronger frame materials allow for better design.

Because Ultrex fiberglass is so strong, Infinity by Marvin windows can use narrower frame profiles that provide:

• More visible glass area
• Better outdoor views
• More natural light
• Cleaner sightlines
• A more refined appearance

Fibrex composite frames are significantly thicker. This is especially important when replacing original wood or aluminum windows that already have narrow profiles. A bulkier replacement window can reduce glass area and noticeably change the appearance of the home.

For homeowners who care about architectural character, light, view, and curb appeal, Infinity by Marvin’s fiberglass frame design is a meaningful advantage.

Long-Term Performance: Stability, Seals, and Efficiency

The biggest material differences often show up over time.

As temperatures change, window frames expand and contract. Excessive movement can place stress on the glass seals, weatherstripping, locks, operating systems, and frame joints.

Ultrex fiberglass expands minimally and at nearly the same rate as glass, helping the frame and glass unit work together as a more stable system. This supports:

• Better long-term frame stability
• More reliable operation
• Stronger seal performance
• More consistent comfort and efficiency

Glass packages matter, but glass alone does not determine window quality. Long-term performance depends on the full system: a stable frame, quality components, proper installation, and a well-built glass package.

Fibrex composite is more stable than basic vinyl, but because it is still a vinyl-containing composite, it still falls short of the thermal stability provided by Ultrex fiberglass.

Component Quality and Everyday Operation

Component quality affects how well a window opens, closes, locks, seals, and feels in everyday use. Important components include the hardware, locking system, balance system, weatherstripping, seals, and operating system.

A premium replacement window should feel solid, smooth, secure, and well-built.

This matters when comparing Infinity with the Andersen 100 Series. The 100 Series is built to meet a lower price point, so it typically has a more basic feel, simpler components, and a less refined overall appearance.

Renewal by Andersen offers a more complete replacement window system than Andersen 100.

Infinity by Marvin combines a premium fiberglass frame with high-quality replacement-focused components designed for strong long-term performance.

Warranty Comparison

A warranty does more than protect the homeowner. It also reflects how confidently a company stands behind its product.

When comparing warranties, homeowners should look at the major areas of coverage: frame, glass, hardware, transferability, and exclusions.

All the above warranties are transferable with limitations. Infinity by Marvin stands apart as the strongest warranty covering lifetime for frame and component parts.

Long-Term Value and Avoiding Regret

Windows are a long-term investment. Products that may seem similar at first can feel very different after installation and over years of ownership.

Some homeowners find that the Andersen 100 Series does not meet expectations for a premium replacement window, often because of its thicker frames, simpler hardware, and less refined overall finish. While it carries the Andersen name, it is still a more budget-oriented product designed around affordability. In many cases, a higher-quality vinyl window may feel more refined or perform better than the Andersen 100 Series.

Renewal by Andersen is different from the Andersen 100 Series in how it is marketed and sold. It is offered through a dealer network with heavy advertising and a highly structured direct-sales model. These added costs help explain why Renewal by Andersen quotes are often among the highest in the replacement window industry. Some homeowners later question that premium when they realize the product still uses a vinyl-containing Fibrex composite frame with thicker profiles and less glass area than a true structural fiberglass window.

Choosing Infinity by Marvin helps homeowners avoid two common mistakes: replacing with a builder-grade product because of a recognizable brand name, or overpaying for a vinyl-containing composite product because of a direct-sales model.

For homeowners who plan to stay in their home and want a premium replacement window, Infinity by Marvin offers a stronger balance of curb appeal, glass area, durability, performance, and warranty protection. Its narrower frames, refined appearance, long-term stability, and Ultrex fiberglass construction make it one of the strongest replacement window choices available.

Written by Neal Burnett for Burnett Home Improvement