Everything about Andersen's Fibrex composite material — what it's made of, how it performs, and which Andersen windows use it.
If you've been researching Andersen windows, you've seen "Fibrex" mentioned repeatedly. It's Andersen's proprietary composite material and a key differentiator from both vinyl and wood windows. Here's what it actually is.
What Fibrex Is Made Of
Fibrex is a composite material made from a blend of reclaimed wood fiber (from Andersen's own manufacturing process) and thermoplastic polymer (PVC). The wood fibers provide structural strength and rigidity while the polymer provides moisture resistance and dimensional stability. The result is a material that's approximately twice as strong as vinyl but doesn't rot, flake, or blister like wood.
How Fibrex Performs vs Vinyl vs Wood
- Strength: Fibrex is roughly 2x stronger than vinyl, allowing for narrower frame profiles (more glass, more view) without sacrificing structural integrity
- Thermal expansion: Fibrex expands and contracts significantly less than vinyl in temperature extremes — important in Illinois where temperatures range 100+ degrees between summer and winter
- Moisture resistance: Unlike wood, Fibrex doesn't absorb moisture, so it won't rot, warp, or swell
- Paintability: Fibrex can be factory-painted in a range of colors with a durable finish that holds up to UV and weather
- Environmental: Made with 40% reclaimed wood fiber that would otherwise be waste from Andersen's manufacturing
Which Andersen Windows Use Fibrex?
The Andersen 100 Series is the primary Fibrex product line — it's Andersen's most affordable option and uses Fibrex for both the interior and exterior frame. Renewal by Andersen (a separate company) also uses Fibrex exclusively. The Andersen 200, 400, E-Series, and A-Series use different materials (wood, Perma-Shield, aluminum-clad, and fiberglass). Full Andersen product line review →
How each material ages here
Vinyl expands and contracts more than other frame materials, and over decades that movement works on seals and corners; quality lines with welded corners and thicker walls hold up far better than builder-grade. Fiberglass and Fibrex move very little, so seals last and darker colors are possible. Wood is the best insulator and the most beautiful, but it must be protected from water by cladding and maintained inside.
Choosing by priority
If the lowest cost with no upkeep is the goal, choose a good vinyl window. If you want narrow frames, dark colors and long-term stability, choose Fibrex or fiberglass. If the interior of the house has stained trim or period character, choose wood-clad. Many customers mix: wood-clad in the front rooms where it shows, composite elsewhere.
How to compare window quotes fairly
Two quotes for the same house can differ by thousands and both be honest, because they describe different things. Line them up on the same points: the exact product line, not only the brand; frame material; glass package and U-factor; insert or full-frame installation; what happens to interior and exterior trim; and who installs. A premium brand's entry line is not the same window as its top line, so compare series to series.
Why the installer matters more than the label
Every major manufacturer makes a good window. Whether it performs depends on the opening being measured exactly, the unit set square, the gap insulated and the exterior flashed. Manufacturer warranties also expect installation to their instructions. We are an Andersen Certified Contractor and install Marvin, Pella and Kolbe with the same crews, which lets us recommend by house, not by quota.
Common questions
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