Vinyl vs Fiberglass Windows


The price tag is a main differentiator.

Fiberglass and composite windows are the newer “premium” options to hit the market in the past 20 years. These windows justify their price tag when compared to the bargain brand vinyl window. But, compare high-quality vinyl vs. fiberglass windows, and the fight is evenly matched, except for the price tag.

Are Fiberglass/Composite windows more energy efficient?

Many home insulation products contain fiberglass. Thus, it would follow that fiberglass windows provide better insulation. And, fiberglass/composite window manufacturers would have you believe that as well.

However, the reality is that the frame material itself is only a small fraction of what makes a window energy efficient. An airtight seal for a better air infiltration rating, multiple air chambers for insulation, and the glass package are the essential part of what makes a window energy efficient.

Airtight seal: vinyl vs. fiberglass

Almost all vinyl windows, including Harvey's, have fusion-welded corners. Meaning the vinyl melts and presses together creating one solid fused-together frame. Therefore, there is no chance of air sneaking through tiny gaps. Harvey has one of the industries best air infiltration ratings.

Fiberglass/composite window corners are held together with brackets or screws. They don’t have the benefit of a fusion-welded, completely airtight construction. Most of these windows have a higher (less quality) air infiltration rating.

Multiple air chambers

A quality frame made with premium vinyl, such as Harvey’s, have multiple chambers. Air is a natural insulator. Thus the more air pockets, the better the insulation. Harvey’s Tribute Double Hung window also has an optional foam insert to increase efficiency even more.

Higher-end fiberglass/composite windows have a similar structure and insulated fill options as Harvey. As such, they’ll tend to compare their window to a bargain brand vinyl window to try and justify the higher cost. However, the reality is that there are premium vinyl windows like Harvey that meet and beat their quality.

Glass is key for efficiency

A window is mostly glass. Therefore, choosing the right glass package and upgrades has a significant impact on energy efficiency. Options such as triple-pane glass, gas-filling, and low-E coatings significantly affect ratings over the material. Make sure to compare a window’s NFRC ratings and compare your options. Look for ENERGY STAR rated glass packages for your climate zone.

Are Fiberglass windows 5-10 times stronger and more durable?

When compared to a flimsy bargain vinyl window? Yes. But again, compare Harvey vinyl vs. fiberglass windows, and the story is different. Harvey windows offer similar or better design pressure (DP) and thermal ratings as the most popular fiberglass/composite windows.

Our windows are engineered to last, and we’ve proven that performance through rigorous tests in our on-site fenestration lab. But the real test is over 50 years of Harvey’s continued success with products that withstand the harshest weather conditions in the northeast.

Durability Comparison

According to, fiberglass windows require more maintenance to prevent them from appearing worn out over time. Installers accidentally damage fiberglass/composite windows frequently. Meaning they need touch-ups and repainting.

With the toughness and flexibility of quality vinyl, you won’t have to worry about the chipping and cracking that fiberglass products can be prone to during installation.

So why pay more for fiberglass windows?

Compare your options. Consider energy efficiency, durability, and style. Look for a reputable manufacturer, who stands behind its products with an exceptional warranty. Harvey windows come with one of the best warranties in the window industry as 

You want a sharp-looking window that reflects all the care, style, and pride you put into your home.

Harvey’s testing and engineering capabilities ensure optimal structural and thermal performance for real-world applications. Our numerous design options allow for customization. And you can count on Harvey. We’ve been standing behind our products and providing quality windows for over 60 years.

Fiberglass windows won’t save you double in energy costs or last twice as long. So why pay twice as much?



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