Why don't they make boats out of vinyl?

Because a boat made out of vinyl would be a very bad idea. Between the beating and pounding of the boat against the water and the heat of the sun, the vinyl would break apart on the first trip to Catalina.

Vinyl frames expand and contract. Vinyl is a soft material and can warp and shift under everyday conditions — potentially making vinyl windows difficult to open and close and affecting their all-around performance.

Vinyl frames expand and contract bend and warp with the changing heat and cold temperatures of everyday conditions, potentially making vinyl windows difficult to open and close and affecting their all-around performance.


ULTREX® fiberglass for unmatched performance

We created Ultrex with one goal in mind: develop the most durable window material in the industry. It's not only 8 times stronger than vinyl — it resists expanding and contracting in any climate. So you get a tight, snug fit that will last.

Vinyl Window Frames Expand and Contract: Vinyl materials are great for many different products, like patio chairs and lawn furniture. However what happens to plastic furniture when you leave it in the sun for a few years? It starts chalking and deteriorates, it warps and falls apart in just a few years. There is a reason boats are made from fiberglass because they take the beating of the ocean waves, the heat of the sun, and the cold of the water, and fiberglass just keeps going. Window Replacement is made for Fiberglass because it's strong and it lasts.


ULTREX Beats All Competitors

References: Stork Technimet/Testing Corporation: #0602-15293, #0512-14889, #0704-19702, #TCT006638P. Precision Measurements and Instruments Corporation: #13043-DS. Tecton: # ESP010521P, "Test Results for Fibrex and Ultrex". Plastics Engineering Handbook of the Society of Plastics Industry, Inc. Fifth Edition. Andersen Fibrex Manual: "A High Performance, High Value Biofiber Polymer Composite Technology". Renewal By Andersen: "Fibrex Material: A Better Alternative, A Better Window". LD = Longitudinal Direction * Highest rate of thermal conductivity shown. Test results range from .10 - .13 for vinyl/wood composite (Fibrex) and .09 - .12 for Ultrex.

Better Replacement Windows

Simply put our thin frames makes Infinity from Marvin the most Elegant Replacement Windows in the US. Infinity from Marvin replacement windows is Rated # 1 in 2019 by JD Powers and associates in Customer Satisfaction with window and patio door manufacturing brands.

Why our Replacement Windows BEAT All Competitors

We make the strongest window replacement frames, with the most elegant finish. Infinity from Marvin windows are made from a Marvin patented pultruded Ultrex fiberglass process that makes our window frames as STRONG AS STEEL 8 times stronger than vinyl and 3 times stronger than other competitors. We add a patented acrylic finish both on the exterior and interior window frames that prevent cracking, peeling, or fading to keep your windows looking beautiful for decades to come.

Our Replacement Windows are just more Beautiful

Instead of bulky wide and unappealing frames with an unfinished corner, we do it the right way. If you compare our beautiful finish to all other window frames you can see the difference in the manufacturing quality, the gorgeous design, the smooth welded corners, and the ultimate sleek finish. You can choose from 7 interior and exterior color options and 8 wood grain options.

VINYL vs Fiberglasss

Comparing Ultrex Fiberglass Window Frames to Vinyl Window Frames. Sliding Doors and French doors require large amounts of heavy glass, your frames must stay true and be strong enough to support all that heavy glass. Southern California temperatures can start off at 40 degrees and reach up to 110 degrees on the same day.

Vinyl frames expand and contract bend and warp with the changing heat and cold temperatures of everyday conditions, potentially making vinyl windows difficult to open and close and affecting they're all-around performance.


The glass expands at a rate of 4.6 the vinyl frames expand at a rate of 30 which is 652% more than the glass. So as the different materials expand at different rates the vinyl expands 652% more than the glass, the frames pull away from the glass which eventually will cause ceil failure in your windows, the argon gas leaks out and your windows are no longer energy efficient. Remember this happens every day they expand in the heat and contract in the cold with the daily temperature changes. In this engineer specification sheet below, you can see the different rates in which each material expands and contracts.

Compare Vinyl Vs Fiberglasss

This photo is a competitor'snew vinyl window frame photo before the installation. View the bad corner welds, the bulky frames, and poor finish. This is something you clearly want to avoid. Vinyl window frames expand and contract from the heat and cold 800 times more than our Ultrex pultruded fiberglass. It expands 652% more than the glass that it frames. The constant expansion and contraction cause the plastic frames to pull away from the glass causing seal failure making the windows incapable of proper energy efficient rating.

Compare Other Composite Windows

Compare Andersen 400 series double hung windows. The Fibrex material is made from vinyl and wood products mixed together to attempt to make a stronger vinyl window. This photo here is there standard corner welding. The bulky unfinished weld job is actually starting to crack in the showroom. Our Ultrex Fiberglass frames are 3 times stronger than this composite frame and 8 times stronger than vinyl.



Let's now compare what happens with Ultrex frames. Ultex expands and contracts almost the same as the glass. When the 4.6 glass heats up it expands toward the Ultrex frame 4.0 which is strong as steel and unmovable. The result is a frame as strong as steel with a thin sleek beautiful design that provides more viewable glass.

Which means that our windows and doors stay tight and true even after extreme temperature swings. Ultrex expands at virtually the same rate as glass and maintains a tight seal, so it's resistant to leaks, seal failures, and stress cracks that can compromise energy efficiency and long-term performance


Ultrex fiberglass windows are as strong as steel, our frames are manufactured thinner, trimer, and sleeker because they are strong. Thinner, sleeker frames result in more viewable glass.

Ultrex fiberglass expands at a 4.0 virtually the same rate as glass, at a 4.6 so our windows stay tight and true. This makes Infinity windows resistant to leaks, seal failures, and stress cracks that can compromise energy efficiency and long-term performance.

Compared to other materials, Ultrex is the strongest window framing material in the replacement industry. This means Ultrex resists bending and flexing — that's confidence Fibrex® and vinyl simply can't match.


The Material You Choose for your windows and doors will have impacts far into the future.

Your window and door choice affects your energy efficiency, the security of your home, even the quality of your life. It's not a decision that should be made lightly. Our advice? Study the facts and choose wisely


Vinyl has a high rate of expansion and contraction compared to glass. This can lead to seal failures and stress cracks. Some vinyl/wood composites are 60% vinyl infused with wood fibers and struggle from similar performance issues as their vinyl counterparts.


Infinity windows and doors are built with Ultrex, a highly durable, state-of-the-art, pultruded fiberglass material with acrylic capping. This pioneering technology benefits from 20 years of proven performance in the field


Vinyl can warp and shift under everyday conditions — potentially making vinyl windows difficult to open and close and affecting their all-around performance. Ultrex resists sticking, swelling, and warping so Infinity windows and doors will continue to easily open and close.

Vinyl frames must be manufactured thicker wider, bulkier in order to support the heavyweight of the glass. Because vinyl needs thicker wider frames in order to support the heavy dual-pane glass the result is more frame and less viewable glass.

Ultrex vs. Wood

Wooden windows offer classic beauty that, depending on the environment can require maintenance and care. Infinity windows capture the beautiful details and profiles of wood — without the maintenance.


More view for your money

Ultrex® fiberglass not only provides unmatched durability compared to other window replacement materials, but it also makes a lasting impression both inside and out. From narrower profiles that deliver bigger views and more daylight to color options that resist fading, Ultrex simply delivers.

Because ULTREX® is so strong, we actually use less material in Infinity window frames. That means you get more daylight, more view of the outside, more glass, without bulky materials obstructing your view. We pay extra attention to the details that matter — like our clean, non-welded, corners that let you make the most of your beautiful view.

ULTREX® exclusive patented Fiberglass frames are as strong as steel so they are thinner sleeker and more elegant which results in more viewable glass with a sleeker frame.

Beauty that lasts

Infinity from Marvin is the only company that applies this proprietary, high-performance, co-extruded acrylic finishing process which is unlike anything else in the industry. Our propriety thick, even acrylic Finish is free of pinholes, striations, and imperfections and will resist scratches, fading and chalking to retain its original beauty. This propriety acrylic Finnish is applied both to the outside and inside frames for added protection from the harsh sun and weather.

A Finnish That Resists Fading

Want long-term color retention in a variety of styles? Ultrex uses an acrylic finish that is paintable, fade-resistant and virtually maintenance-free. With a finish that's 3 times thicker than competitive options, Ultrex resists chipping, denting or peeling.



Made from a safe and natural resource. Ultrex is made from silica sand the most abundant natural resource in the world - The Ultrex manufacturing facilities fully comply with the 1990 Clean Air Act and are designated as a Maximum Achievable Control Technology (MACT) facility as outlined by the EPA.

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