Aluminum vs Fiberglass Windows
Choosing between aluminum vs fiberglass windows can be a tough decision. Let's compare and contrast these two window frame materials in terms of their overall looks, strength, window pricing, and energy efficiency.
Summary On Aluminum Windows - by far the strongest frame on the market, nearly 4X as strong as fiberglass. However, they are very bad performers when it comes to their energy efficiency. While aluminum windows don't count for a big portion of the residential market, they are an excellent choice for very hot climates.
Summary On Fiberglass Windows - make for an excellent frame material as they are slim, attractive and quite durable. Fiberglass windows are an excellent option if you can afford their 35% mark up over premium vinyl windows.
Review By John M. - Site Editor - Page Updated In January, 2025
Aluminum vs Fiberglass Windows On Aesthetics
Both aluminum and fiberglass windows are typically slender and very nice looking (certainly compared to vinyl). Aluminum is often considered a very modern looking material and can be made quite narrow due to its unmatched strength.
Fiberglass tends to be a bit thicker than aluminum, but is often quite a bit slimmer than vinyl. Fiberglass looks somewhat nicer than vinyl, but not by a ton. Still, both of these materials are nice looking, although they pale in comparison to wood windows, which are by far the nicest looking frame material on the market.
The Winner: Aluminum
Fiberglass vs Aluminum Windows Cost
Aluminum and fiberglass windows are going to be fairly similar in terms of price. Generally, quite a bit more than vinyl window prices, but less than wood window costs. As a rule of thumb, both of these window frames will run approximately 35 percent more than premium vinyl windows.
Of course, window dealers can quotes our projects at whatever price point they see fit. This is one of the reasons why we always advise consumers to collect a handful of bids prior to pulling the triggers.
The Winner: Draw
Overall Strength
Aluminum is roughly 4X as strong as fiberglass. In fact, aluminum windows are by far the strongest window frame material available today. Specifically, this is the reason that aluminum is required on all commercial window projects.
However, windows are not load bearing, so in nearly all cases, they simply have to support their own weight (and not bow over time). Both aluminum and fiberglass windows offer more than enough strength for 99% of all residential projects.
The Winner: Aluminum
Energy Efficiency
Simply put, aluminum windows are by far the least energy efficient window frame on the market. Metals conduct both heat and cold. Therefore, the material is quite inefficient.
On the other hand, fiberglass is quite energy efficient, definitely one of the best performers out there. I still think the very high end vinyl windows are the most energy efficient, but fiberglass is close behind (especially long term).
The Winner: Fiberglass (by a lot)
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