Replacement Window GuideAndersen and Marvin are two long-established American window makers that anchor their brands on different frame materials. This page lays out what each company states on its own site so you can see where they describe themselves differently on paper.
How to read this comparison
The facts below come from each manufacturer's own website. A brand's site is a primary source for what it builds and claims, but it is also marketing, so treat material claims as company positioning rather than independent test results. For the numbers that decide energy performance, U-Factor, SHGC, and Air Leakage, read the NFRC label on the exact product and glass package you are quoted, because those figures are independently tested and change by configuration. We do not name a winner. Different climates, budgets, and priorities can reasonably land on either brand.
What Andersen publishes
Andersen builds its identity around its Fibrex composite. On its windows overview the company states that contractors agree windows made of Andersen's Fibrex composite material outperform vinyl windows, and it identifies as an ENERGY STAR Partner of the Year.
Andersen organizes its residential lineup into series including the 100 Series, 200 Series, and 400 Series. Its flagship 400 Series is a wood window; Andersen states 400 Series products are primarily made from wood with a Perma-Shield exterior cladding.
What Marvin publishes
Marvin foregrounds its Ultrex pultruded fiberglass. The company states that Ultrex and Marvin High-Density Fiberglass are created through a process called pultrusion, and that Ultrex fiberglass is 8x stronger than vinyl and 3x stronger than wood/vinyl composites.
Marvin also emphasizes thermal stability and a certified finish, stating that Ultrex fiberglass can withstand extreme temperatures up to 285 degrees Fahrenheit while keeping its shape, and that the finish is AAMA 624 verified. Marvin offers its windows in fiberglass, aluminum, and wood.
Where they differ on paper
The clearest documented difference is the material each brand builds its story around. Andersen leads with its Fibrex composite and a wood-core flagship in the 400 Series, stating Fibrex outperforms vinyl. Marvin leads with Ultrex pultruded fiberglass, stating it is 8x stronger than vinyl and 3x stronger than wood/vinyl composites.
Both companies therefore make a case against ordinary vinyl, but they do it with different proprietary materials, a composite versus a fiberglass. Because both sell certified products, the decisive energy numbers still come from the NFRC label on the exact model and glass package you are quoted.