We serve a lot of homeowners who are building new homes or replacing their windows. Marvin’s premium fiberglass windows are often first choice because of their:
Customization options
Large window and door sizes
Long-term durability
Low-maintenance features
Energy efficiency
Long lifespan
First, we’ll explain Marvin’s Ultrex and High-Density Fiberglass, and then we’ll take a look at reasons why homeowners choose Marvin fiberglass windows and doors.
What is Marvin Ultrex Fiberglass?
Marvin’s most well-known fiberglass, Ultrex is made from a proprietary formula that combines fiberglass strands and resin under intense heat and pressure to create a uniformly strong frame. It significantly outperforms other common window materials, coming in over 3x stronger than vinyl and wood composites and nearly 8x stronger than vinyl windows.
Marvin offers two collections featuring Ultrex Fiberglass. Both lines offer stock sizes as well as custom options, so they provide excellent solutions for either replacement windows or new construction.
Marvin Essential Collection: Featuring Ultrex fiberglass interiors and exteriors, this collection offers clean lines, modern styling, and straightforward maintenance.
Marvin Elevate Collection: Combining an Ultrex fiberglass exterior with a rich wood interior, this collection offers the low maintenance and strength of fiberglass with the warmth and beauty of real wood inside the home.
Ultrex is also available through Marvin Replacement and Infinity by Marvin, two branches of the Marvin company.
Window Types Available in Ultrex Fiberglass
Double-hung windows
Single-hung windows
Casement windows
Awning windows
Glider windows
Picture windows
Round top windows
Specialty shape windows
Bay windows
Door Types Available in Ultrex Fiberglass
Sliding doors (patio doors)
Sliding French doors
Inswing and outswing doors
Scenic bi-fold doors
What is Marvin High-Density Fiberglass?
High-density fiberglass is an advanced fiberglass specifically engineered to create custom design configurations. It was developed for Marvin's Modern Collection, which emphasizes minimalistic design and expansive glass.
Because high-density fiberglass supports larger spans and heavier glass, it allows architects and designers the flexibility to create large-scale window and door systems without compromising performance or aesthetics.
The Modern Collection features high-density fiberglass exteriors with low-gloss aluminum interiors. Available in five colors, the finish is baked on at extremely high temperatures, resulting in a finish that exceeds a high-quality aluminum car paint.
Window Types Available in High-Density Fiberglass
Casement windows (automation available)
Awning windows (automation available)
Direct glaze windows
Specialty shape windows
Push out windows
Corner windows
Door Types Available in High-Density Fiberglass
Inswing and outswing doors
Multi-slide doors
Why Homeowners Choose Marvin Fiberglass
We get a front row seat to the window buying process from the research phase until after installation. Homeowners who choose Marvin’s fiberglass over vinyl or vinyl composites are usually looking for the enhanced durability and larger sizes available in fiberglass. And the decision to choose fiberglass over wood is often based on the style of the house.
Let’s explore why Marvin fiberglass windows and doors could be the right choice for your new windows or window remodel.
Large Window Panels and Narrow Frames
Because Marvin’s fiberglass is so strong, it can support oversized window and door sizes. This allows for bigger glass areas with narrower frames and sashes, which means more natural light and wider views.
Whether it’s a wide-span multi-slide door or expansive picture window, Marvin fiberglass holds its shape without sagging, warping, or compromising performance—making it a practical option for modern designs that call for clean lines and open spaces.
The Science Behind Marvin’s Fiberglass Strength
Marvin’s fiberglass is made through pultrusion—fiberglass strands are heated and pulled through (pultruded) to form the window material. The result is a strong and durable window frame that withstands the elements.
Fiberglass is a thermoset material, meaning its properties remain constant regardless of temperature changes. (By comparison, Vinyl and vinyl-/wood composites are thermoplastic, so they flex in extreme heat or become brittle in cold.)
When put through stress tests, Marvin’s thermoset fiberglass has been found to be as strong as steel. That strength enables Marvin to build windows that are larger, more custom, and longer lasting!
Tough Acrylic Finish
Marvin’s proprietary acrylic finish is available in multiple colors, and it’s fade resistant. The first to achieve AAMA 624 verification, it has passed rigorous tests simulating harsh conditions over time. Even 48,000 hours of sun didn’t fade this acrylic finish!
We’ll talk more about durability in a moment, but it deserves a mention here as well. A key benefit of Marvin’s acrylic finish is its thick, even finish that resists scratches, denting, chalking, and fading. While many composite materials in dark finishes like black or bronze are damaged by high sun exposure, Marvin’s fiberglass products offer popular dark colors with best-in-class protection against UV degradation.
Durability
Marvin’s fiberglass stands out because it expands and contracts at nearly the same rate as glass which reduces stress on seals and joints. Repeated expansion and contraction over time can cause seal failures, warping, leaks, and gaps in less stable frames like vinyl.
Their overall strength also means the frames are less likely to flex or bow, which plays a big role in preserving energy efficiency, functionality, and smooth operation. We all like a window that opens and closes easily!
Energy Efficiency
Marvin was the first major window and door manufacturer to offer Low E2 glass and Energy Star certified performance on all standard windows and doors. In addition to the glass, there are two primary ways fiberglass windows increase energy efficiency: low expansion rate for tighter seals and low thermal conductivity for less heat transfer.
We recommend combining fiberglass frames with energy-efficient glass options like dual panes, Low-E coatings, and insulating gas fills to maximize the thermal performance of your windows and doors.
Low Maintenance
Fiberglass does not rot, warp, or corrode, eliminating the ongoing maintenance tasks typically associated with wood windows. The smooth, rock-hard acrylic finish is easy to keep clean—usually requiring nothing more than mild soap and water.
Long Lifespan
Unlike materials that may degrade, warp, or weaken over time, Marvin fiberglass holds up for decades—even in challenging climates. This makes it a reliable option for homeowners who want to avoid the cycle of frequent repairs or premature replacements.
Resistance to moisture, UV exposure, and temperature-related stress helps maintain the structural integrity and energy efficiency of the window or door over the long haul. Marvin backs this performance with a limited lifetime warranty, which reflects both confidence in the material and a track record of real-world durability.
Resistance to moisture, UV exposure, and temperature-related stress helps maintain the structural integrity and energy efficiency of the window or door over the long haul. Marvin backs this performance with a limited lifetime warranty, which reflects both confidence in the material and a track record of real-world durability.
Experience Marvin Windows Firsthand
Customers tell us that visiting a showroom helped them really understand their window options. See specific styles, touch the windows, and ask ALL of your questions—it’s the best way to make a decision!
As the largest supplier and installing retailer of Marvin Windows in the Northeast, Ring’s End offers an elevated shopping experience:
Free consultations at any of our eight showrooms that feature dozens of window and door styles.
Window and door experts will help you plan your project and place the order.
Licensed window installation services for both new construction and window replacement projects, serving Connecticut, Westchester County, NY, and South County, RI.
Stop by one of our showrooms or schedule a consultation! We’re here to help with lots of information but no pressure.