- Aluminum windows are sleek and modern but very poorly insulated from heat and cold.
- Fiberglass windows can cost slightly more upfront but provide great energy savings and a versatile look.
- Both types are highly durable, long-lasting, and low-maintenance.
Aluminum or metal frames are very strong, light, and almost maintenance-free, according to the U.S. Department of Energy. However, they conduct heat easily and offer poor insulation unless designed with a thermal break. Fiberglass frames are dimensionally stable with air cavities that can be filled with insulation, giving them better thermal performance than both metal and wood.
Pure aluminum frames are rarely used in residential construction due to their poor efficiency, but they may be suited to very modern home designs in mild climates. More commonly, homeowners choose aluminum-clad windows, which have a wood interior and aluminum exterior. These cost $400–$850 per window, on average. Fiberglass frames offer superior energy savings for a slightly higher cost of $500–$1,000, on average.
For most homeowners, fiberglass windows offer better insulation and long-term value, with a minimal price difference. Below, we break down some other key differences between these two window materials, such as maintenance and appearance, to help you decide which is best for your home.
Aluminum Vs. Fiberglass Windows: What’s the Difference?
The biggest difference between aluminum and fiberglass frames is their energy efficiency. Aluminum frames are rarely used without modification due to their lack of efficiency, while fiberglass frames offer much better insulation.
It’s worth noting that aluminum windows differ from aluminum-clad windows. The former are typically all-metal frames used in modern or commercial-style homes, while aluminum-clad windows combine a durable aluminum exterior with a wood interior. Aluminum-clad windows are more common, and usually more affordable, than fiberglass. However, full aluminum frames, especially high-performance thermally broken ones, can be quite pricey — sometimes even more than fiberglass.
The table below shows how common aluminum-clad and fiberglass windows stack up across factors such as maintenance and appearance.
| Factors | Aluminum-Clad Windows | Fiberglass Windows |
|---|---|---|
| Energy efficiency | Poor efficiency; require the addition of thermal breaks | Well-insulated and highly efficient |
| Cost | $400–$850 | $500–$1,000 |
| Maintenance | Low maintenance; may require anticorrosion coating | Low maintenance in all climates |
| Lifespan | 40–50 years | 30–50 years |
| Appearance | Thinner, modern, industrial | Varies, can mimic other materials |
Energy Efficiency
Windows play a key role in a home’s energy efficiency, and the material greatly affects an individual window’s efficiency.
“Aluminum windows are not something you are going to find for new or replacement windows outside of commercial applications due to their lack of energy efficiency,” said Alex Vinet, client services specialist for Custom Exteriors in Berthoud, Colorado. This is because aluminum naturally conducts heat. Modern aluminum frames are often modified to include thermal breaks, which improve their insulation properties but also greatly increase costs.
Aluminum-clad wood windows offer better efficiency than just aluminum because wood is a better insulator. However, fiberglass windows are the most efficient insulators overall due to their low conductivity and ability to incorporate additional insulated pieces as part of the frame.
Cost
Pure aluminum window costs are among the highest for window frame materials, although aluminum-clad windows are in the same ballpark as fiberglass windows. Aluminum-clad windows cost around $400–$850, while fiberglass windows cost $500–$1,000.
“Vinyl is the most cost-effective window material, and I’d say 85% to 90% of the market uses vinyl,” Vinet said. However, vinyl windows aren’t as durable as aluminum or fiberglass windows.
| Window Frame Material | Average Cost per Window Installed |
|---|---|
| Vinyl | $450–$800 |
| Aluminum-clad | $400–$850 |
| Fiberglass | $500–$1,000 |
| Composite | $500–$1,200 |
| Wood | $600–$1,500 |
Today’s Homeowner Tip
How much you’ll pay for your replacement windows often comes down to the brand, product line, window size, and installation — not just the frame material.
Maintenance
Aluminum and fiberglass are both low-maintenance window frame options. Fiberglass windows don’t require paint or finish and are easy to clean with mild soap and water. They are fade-resistant, but they are susceptible to damage from excessive sun exposure.
“Darker colors will fade and discolor faster in direct sunlight,” Vinet explained. “The more sun exposure fiberglass has, the faster it will break down, leading to possible chipping, fading, or peeling, depending on the manufacturing process and additives the manufacturer has used.”
Aluminum windows are also easy to clean, but they do require some extra care. You need to keep moving parts lubricated, and in coastal areas, they may require an anticorrosion coating for protection from the elements. They don’t do well in extreme temperatures.
Lifespan
Aluminum windows have an average lifespan of about 30 to 50 years, though this depends on how well they’re maintained.
Fiberglass windows have a similar average lifespan of about 30 to 50 years or even longer.
“With proper maintenance, aluminum-clad windows could outlast fiberglass windows,” Vinet said, then added, “I feel that this type of window requires the most maintenance of all window types.”
In either case, you’ll need to regularly clean and maintain your windows according to manufacturer recommendations to maximize how long they last before replacement is required.
Appearance
Completely aluminum windows have a sleek, modern appearance with thin frames that allow for a large glass area. They are often used in commercial or industrial designs. Aluminum-clad wood frames have a much thicker frame depth and height, which creates a bulkier look with less glass space and an overall more traditional appearance.
Fiberglass windows are versatile enough to fit a range of architectural styles, often manufactured to resemble other materials. For example, some fiberglass windows feature a faux wood grain texture.
Advantages and Disadvantages of Aluminum Vs. Fiberglass Windows
Aluminum and fiberglass windows are both low-maintenance options offering long lifespans and great durability. Consider the following pros and cons of fiberglass and aluminum when deciding between them.
Aluminum Windows
Pros
- Highly durable
- Very strong and light
- Low-maintenance
- Tend to cost less than fiberglass windows
Cons
- Very poor insulator, especially in climates with extreme temperatures
- Prone to condensation and corrosion from moisture
Fiberglass Windows
Pros
- Highly energy-efficient with air cavities that can be filled with insulation
- Offers long-term energy savings
- Long-lasting, durable, and low-maintenance
- Suited to various climates and weather conditions
Cons
- Tend to cost more than aluminum-clad windows
- Relatively few design options for customization
Are Aluminum or Fiberglass Windows Best for You?
In many homes, fiberglass windows are a better option than aluminum windows. Aluminum is a poor insulator in most climates. Fiberglass is far more versatile and among the most efficient windows, offering better energy savings. It’s well-suited to nearly any climate and architectural style. We recommend fiberglass windows for energy-conscious homeowners who want lower heating and cooling costs over time.
Today’s Homeowner Tip
The best type of window frame for your project will also depend on factors such as brand, series, and installation quality.
You may prefer aluminum-clad windows if you enjoy their style or want to save a bit on your window replacement project and still get a durable, low-maintenance window.
Next Steps
If you’re considering new windows for your home, talk to a local window supplier or general contractor specializing in exteriors. They’ll be able to assess your home and advise you on the best material for your unique project. Gather quotes from multiple contractors so you can compare their costs, services, and reputation from past work.
If cost is your primary concern, vinyl windows may make an even better budget window replacement. Vinyl offers a good balance between efficiency and affordability.
FAQs About Aluminum Vs. Fiberglass Windows
Do aluminum or fiberglass windows have better resale value?
Both aluminum-clad and fiberglass windows are considered premium options and can improve home resale value — especially if they enhance curb appeal and energy efficiency.
Fiberglass windows may offer a slight edge due to their long-term performance and growing popularity among energy-conscious buyers. However, well-maintained aluminum-clad wood windows can also make a strong impression, particularly in traditional or Craftsman-style homes.
What should I look for when buying windows?
When buying windows, you should look for dimensions that specifically match your accurately measured window opening. A professional window specialist can take the most accurate measurements of a window’s width and height from the home’s exterior. Mistakes and mismeasures can be costly, since you cannot return most window orders once removed from the packaging.
Which company is the best for windows?
The best window brands include Renewal by Anderson, Pella, Marvin, Champion Windows, Window Nation, Universal Windows, Window World, and Castle Windows. Many companies partner with specific brands, so talk to multiple suppliers in your area to find one with the types of products you’re looking for at a price within your budget.
For example, if you’re looking for aluminum-clad windows, Pella and Marvin are both options. However, Pella’s aluminum-clad windows are more expensive.
