Georgia's heat, humidity, and strong sunlight can place added stress on window materials. When comparing Fibrex® and fiberglass windows, understanding how each material responds to these conditions can help homeowners make a more informed decision.
This guide compares Fibrex and fiberglass, specifically Ultrex® fiberglass, by examining durability, energy efficiency, maintenance needs, and long-term performance—so you can choose what works best for your home and climate.
This guide compares Fibrex® and fiberglass windows by looking at their durability, energy efficiency, and maintenance, so you can choose what's best for your home.
What is Fibrex?
Fibrex is a composite material made up of 40% wood and 60% plastic. It is a thermoplastic material, which is a substance that becomes pliable on heating and hardens on cooling, and then it's able to repeat this process.
Fibrex is not fiberglass.
What is Fiberglass?
Fiberglass is a type of fiber-reinforced plastic using glass fibers. These fibers can be arranged differently in the manufacturing process.
Enter Infinity by Marvin's Ultrex fiberglass. This manufacturing process is what separates their product from just any type of fiberglass. Thin strands of strong glass cables are saturated with compounded resins. These cables are then pulled through a heated die and cut with diamond-edged blades to form the Ultrex material. Lastly, a proprietary acrylic finish is applied that prevents Ultrex from needing any painting, although it still remains a paintable product if desired.
Ultrex is a thermoset material, meaning once their components and physical properties reach a certain temperature and cure, they become set. Their properties can't be melted back down or restored to their original state. This means doors and windows made of Ultrex fiberglass will not melt or lose their true shape, even when exposed to extreme temperatures of up to 285° F. It also means they perform under all types of weather.
Performance in Georgia's Humidity and Heat
Georgia's climate places real demands on window materials. Prolonged heat, high humidity, and strong sun exposure can cause some frame materials to expand, soften, or lose structural stability over time.
Fibrex, a thermoplastic composite, can be more sensitive to heat-related expansion. As materials expand and contract, seals may be placed under added stress, which can affect long-term performance.
Ultrex fiberglass is a thermoset material designed to maintain its shape and strength across a wide temperature range. This stability helps window frames remain tight and reduces the risk of air leakage in hot, humid conditions.
What are the pros of Fibrex windows?
- Fibrex windows do not need to be painted, nor will they rot.
- Fibrex can be formed into many different profiles.
- Fibrex is twice as strong as vinyl.
What are the cons of Fibrex windows?
- Fibrex windows can bow and warp.
- Despite being twice as strong as vinyl, Fibrex windows still have thick frames, which means it cuts into your daylight and views.
- Fibrex windows often come with double locks and double lift rails on double-hung and slider windows, which create a cluttered view.
- As mentioned above, Fibrex is thermoplastic. These types of materials have low melting points, which means they cannot withstand as high temperatures as thermoset materials.
- Fibrex (the window frame material) and the glass are made from two different components; therefore, they expand and contract at different rates. As the frame expands and contracts, the seal that protects the two panes of glass can become compromised, causing moisture to build up between the two panes, leading to seal failure and other issues.
What are the pros of Ultrex fiberglass windows?
- Ultrex fiberglass can be formed into many different profiles, including shapes.
- It is 8x stronger than vinyl and 3x stronger than Fibrex. This means the replacement window frames are more narrow, allowing for more daylight and bigger views than other replacement windows on the market.
- Because of this strength, Ultrex fiberglass windows only have one lock on their double-hung and slider windows, creating a clean and obstructed view.
- The Ultrex fiberglass replacement window frame and the glass are both made from the same basic material - silica sand. This means that they expand and contract at nearly the same rate, ensuring the windows stay tight and true and making the Infinity window resistant to leaks, seal failures and stress cracks.
- The Ultrex fiberglass proprietary finish is 3x thicker than the competition. This means no sanding, scraping or painting is required. Also, it will not rot.
Energy Efficiency and Comfort in Every Season
In climates with hot summers and mild winters, maintaining a tight window seal plays a key role in energy efficiency. Materials that resist expansion and contraction are better able to keep conditioned air inside the home.
Ultrex fiberglass frames are designed to maintain consistent shape under temperature changes, helping windows remain sealed and reducing energy loss over time. Fibrex windows can provide energy efficiency as well, but differences in material behavior may affect long-term performance in hotter, more humid conditions. As it expands and contracts, the seal can weaken over time, which can make your home use more energy to stay comfortable. As it expands and contracts, the seal can weaken over time, which can make your home use more energy to stay comfortable.
When deciding between Fibrex and Ultrex fiberglass, it's important to think about both the initial cost and the long-term savings and comfort. Infinity by Marvin windows are reliable and help keep your home comfortable all year, making them a smart pick for Georgia homeowners who want to save energy and money.
What are the cons of Ultrex fiberglass windows?
Because of its performance, it is a premium product and is therefore more of an investment than other replacement windows. However, it is a product that it is Built for Life®, and is worth considering when compared to the money spent on maintaining and upkeeping other types of windows. Fibrex vs. Fiberglass. And, more specifically, Fibrex vs. Ultrex.As you can see, the most common similarities the two have are in their names and phonetics. Beyond that, it is clear to see the differences between Ultrex and Fibrex replacement windows.
Understanding the differences between Fibrex and fiberglass helps homeowners evaluate long-term durability, maintenance needs, and performance in demanding climates. While both materials offer benefits, Ultrex fiberglass is engineered for strength, dimensional stability, and resistance to heat and humidity—factors that are especially important in the Southeast.
Choosing the right window material is an important step in any replacement project. Evaluating how each option performs over time can help ensure your investment delivers lasting comfort and reliability.
The Local Difference: Professional Installation Matters
In Georgia, how your windows are installed matters just as much as the materials you choose. Even the best windows won't work well if they aren't installed properly, especially with all the moisture and temperature changes.
NG Windows has the local know-how to handle these challenges. Our certified installers focus on sealing your windows carefully, which is key to stopping air leaks and moisture. This careful work helps your windows stay strong and energy efficient for years.
We customize every installation to fit your home, making sure your windows are ready for Georgia's tough weather. We focus on quality by choosing the right materials and making sure the installation is seamless.
When you choose Infinity by Marvin windows and our expert installation, you get great performance and peace of mind. We're here to give Georgia homeowners strong, long-lasting windows, backed by our local experience and dedication to quality. You can count on us to install windows that handle the Southeast's tough climate.
To learn more about replacement windows and what is the best window to install, contact us today to schedule your free consultation.
Fibrex® is a registered trademark of Andersen Corporation. Ultrex®is a registered trademark of Marvin Lumber and Cedar Co., LLC.
