For most Greenburgh homeowners replacing windows in a 1950s–1970s Colonial or ranch, the Andersen 100 Series is the practical choice — lower cost, extremely low maintenance, and a Fibrex composite frame that handles Westchester County’s freeze-thaw cycles well. The Andersen 400 Series is worth the step up when you want a genuine wood interior, more configuration flexibility, or a period-appropriate look in an older home. Neither is a wrong answer; the decision hinges on what you’re actually optimizing for.

The Quick Comparison

Both series are manufactured by Andersen, and both can be specified to clear the 2020 NYS Energy Code’s Climate Zone 4 U-factor threshold of 0.32 and SHGC of 0.40 (per 2020 NYS ECCC Table R402.1.2).

What Fibrex Actually Is (and Why It Matters Here)

The 100 Series is built around Andersen’s proprietary Fibrex composite material: roughly 40% reclaimed wood fiber combined with 60% thermoplastic polymer (per the Andersen Fibrex material page). That composition gives the frame about twice the stiffness of vinyl while resisting the rot, flaking, blistering, and peeling that can plague painted wood windows over time.

For Westchester’s climate — hard winters, humid summers, the occasional nor’easter — that durability profile is meaningful. A Fibrex frame doesn’t need the periodic scraping and repainting a wood frame requires, which reduces your long-term maintenance commitment.

What the 400 Series Gives You That the 100 Series Doesn’t

The 400 Series uses a real wood interior with Andersen’s Perma-Shield vinyl-clad exterior (per the Andersen 400 Series product page). That means:

• Interior finish flexibility. You can paint or stain the interior sash to match your trim exactly — a big deal in Colonials with detailed millwork, where a factory composite color can read as mismatched.
• Broader configuration options. The 400 Series covers a wider range of sizes, operating styles, grille patterns, and hardware finishes. If you’re matching existing divided-light patterns or need an unusual rough-opening size, the 400 Series typically offers more paths.
• Period character. In a pre-1960 home with original wood windows, owners who want to preserve the visual weight and shadow profile of a wood sash often find the 400 Series closer to the mark.

The trade-off is ongoing care of the interior wood surface and a moderately higher installed price.

Energy Code Context for Westchester (Climate Zone 4)

Westchester County sits in IECC Climate Zone 4 under New York State’s 2020 Energy Conservation Construction Code. The prescriptive minimum for new window installations is a U-factor of 0.32 or better and SHGC of 0.40 or better (2020 NYS ECCC Table R402.1.2). Both the 100 Series and the 400 Series can be specified to meet or exceed that threshold.

If you’re targeting ENERGY STAR v7.0 qualification — the tighter benchmark since October 2023 — the Northern climate zone criteria tighten significantly to U-factor ≤ 0.22 and SHGC ≥ 0.17 (per the ENERGY STAR v7.0 final specification). Not every configuration of either series will hit those numbers off the shelf; that’s a spec-time conversation with your installer. NFRC-rated U-factors run roughly 0.20–1.20 on their published scale, with lower values indicating better insulating performance (per NFRC).

For fall window replacement — the right season to button up the envelope before Westchester’s heating season — the energy-code conversation is worth having now rather than after installation.

Greenburgh-Specific Notes: Permitting and Housing Context

Greenburgh’s permitting structure has a wrinkle worth understanding before you start: the Town of Greenburgh Building Department handles window permits for the unincorporated town area, but if your home sits within one of Greenburgh’s incorporated villages — Ardsley, Dobbs Ferry, Elmsford, Hastings-on-Hudson, Irvington, Tarrytown, or Sleepy Hollow — that village maintains its own permitting program (per the Town of Greenburgh Building Department FAQ). Window replacement typically requires a permit; which department you file with depends on your specific address.

Gunner handles the building permit on every project, so that coordination is part of the job regardless of which jurisdiction applies to your address.

The housing stock across unincorporated Greenburgh skews heavily toward postwar Colonials, split-levels, and ranches built from the late 1940s through the 1970s. These homes tend to have older double-hungs in standard rough-opening sizes — which plays to the 100 Series’ strengths. Homes in the villages, especially older Tarrytown and Irvington stock with Victorian-era or early-twentieth-century character, are more likely to benefit from the 400 Series’ wood-interior flexibility and broader configuration range.

When to Step Up to the A-Series

If your project calls for something beyond what either the 100 or 400 Series delivers — wider spans, a premium architectural profile, or a wood interior paired with a fiberglass/composite exterior rather than vinyl cladding — Andersen’s A-Series (the Architectural Collection) is the line above. It uses a wood interior combined with a fiberglass/composite exterior, giving you the structural capacity and customization of a premium unit (per the Andersen A-Series product page). It’s worth considering in renovation projects where window replacement is part of a larger exterior upgrade.

The Bottom Line

• Choose the 100 Series if low maintenance is the priority, you’re replacing standard postwar windows in a Colonial or ranch, and you want strong energy performance at a lower cost.
• Choose the 400 Series if you want a wood interior you can paint or stain, need a wider range of configurations, or are working in a home where the visual character of a wood sash matters.
• Consider the A-Series for premium or architectural projects where you need more than either entry can offer.

Gunner is an Andersen Certified Elite contractor, which means we can spec and install across all three of these series. We pull the permit on every job — and in Greenburgh that means we sort out whether you’re under the town program or your village’s program before anything goes in the ground.

Get a free, no-obligation estimate at GunnerRoofing.com.

Frequently Asked Questions

Q: What is the main difference between Andersen 100 Series and 400 Series windows? The 100 Series uses an all-Fibrex composite frame (inside and out), while the 400 Series has a real wood interior with a Perma-Shield vinyl-clad exterior. The 100 Series requires less ongoing maintenance; the 400 Series offers more interior finish flexibility and a broader configuration range.

Q: Do Andersen 100 or 400 Series windows meet Westchester County’s energy code? Both series can be specified to meet the 2020 NYS Energy Code’s Climate Zone 4 prescriptive threshold of U-factor ≤ 0.32 and SHGC ≥ 0.40 (per 2020 NYS ECCC Table R402.1.2). Whether a specific configuration clears the tighter ENERGY STAR v7.0 Northern-zone criteria (U-factor ≤ 0.22) depends on the exact unit specified — confirm with your installer.

Q: Do I need a permit to replace windows in Greenburgh, NY? Window replacement typically requires a permit in New York. If your home is in unincorporated Greenburgh, the Town of Greenburgh Building Department handles permitting. If you’re in one of Greenburgh’s incorporated villages, that village runs its own program. Gunner pulls and manages the permit on every job (per Town of Greenburgh Building Department FAQ and Gunner policy).

Q: What is Fibrex, and is it better than vinyl for Westchester winters? Fibrex is Andersen’s proprietary composite: roughly 40% reclaimed wood fiber and 60% thermoplastic polymer. It resists rot, fading, flaking, blistering, and peeling, and is about twice as stiff as vinyl (per Andersen). For Westchester’s freeze-thaw climate, the durability profile compares favorably to standard vinyl.

Q: Is the Andersen 400 Series worth the extra cost? For most straightforward replacements in postwar Westchester homes, the 100 Series delivers excellent performance at lower cost. The 400 Series earns its premium when you want a wood interior you can stain to match existing trim, need a wider range of sizes or configurations, or are working in an older home where visual period character matters.

Q: Is fall a good time to replace windows in Westchester County? Yes — replacing windows before Westchester’s heating season means your home enters winter with a properly sealed and insulated envelope. Scheduling installs in September or October gives time for the work to be completed and any sealant to cure before hard freeze conditions arrive.