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Windows & Doors Review: Milgard Fiberglass Windows
Top Choice: Milgard Fiberglass windows offer superior strength and durability, but at a price.

For windows, fiberglass is still an emerging category. But recent advances in technology, as well as the entry of major manufacturers, mean fiberglass window offerings are growing, albeit slowly.

Though still more expensive than its vinyl and aluminum counterparts and comparable to wood, fiberglass' durability and energy-efficient characteristics provide a solid alternative for customers looking for a premium product, manufacturers and contractors say.

"When clients want a higher-end product than vinyl, fiberglass becomes very appealing," says Kurt Schmitz, sales manager for City Glass & Upholstery, an independent dealer and installer in Tacoma, Wash., that offers Milgard's Ultra fiberglass line. Schmitz estimates that fiberglass windows, which cost 20 percent to 30 percent more than comparable vinyl units, account for 5 percent to 10 percent of his sales.

While more expensive, fiberglass windows are worth it, installers say. Because of fiberglass' inherent strengthmanufacturers claim it's eight times stronger than vinyl and twice as strong as steelits higher price often translates into an investment that lasts.

Manufacturers say the material doesn't become brittle from exposure as vinyl can, and that fading, scratching, and warping are virtually eliminated, making maintenance a breeze. Finally, because fiberglass windows maintain their structural integrity over time, meaning frames don't sag and tracks don't jam, builders and remodelers face fewer headaches from callbacks and warranty issues.

"If they're manufactured and installed properly, fiberglass windows should be the last set of windows a home ever needs," says John Schmotzer, owner of Metropolitan Window Co., a window dealer and installer that's been offering fiberglass windows in the Pittsburgh market since 1990. "Once we finish a fiberglass job, typically, I'll never hear from the people again. That's not true with vinyl."

While color variety has been limited in fiberglass windows in the past, the material is paintable, and more manufacturers are starting to powder coat their products in a wider range of hues. With growing interest in the category, many firms now offer casement, single-hung, double-hung, slider, and picture designs with a variety of grilles. Glass options also are numerous, with low-E argon-filled, storm-resistant, and self-cleaning choices available.

Another advantage is fiberglass' ability to serve as an efficient insulator while contracting and expanding at the same rate as the glass in the window itself. Proponents point out that the insulation inside a typical home's walls is a fiberglass-based product, and for good reason.

"If you took a piece of fiberglass and stuck one end into a flame, you could hold onto the other end almost indefinitely. It doesn't conduct heat," says Jay Thomas, owner of Denton, Texas-based J. Thomas Custom Homes, which completes about 25 remodeling and new construction jobs per year.

Thomas' firm started offering Pella's Impervia line in 2004 for both replacement and new construction in his market, where extreme summer temperatures can be murder on energy bills. "A lot of my customers question why they should spend more money on windows in a place where it doesn't get that cold," says Thomas. "But it takes more money to cool a house than heat it. The great thing about fiberglass is there's virtually no thermal bridging from the frame itself, so you have a more comfortable house that's more energy efficient."

Slow to Grow

But for all its strengths, fiberglass has been slow to gain traction. "While it is a growing segment, I'd estimate that it's still less than 5 percent of the overall marketplace," says Jeffrey F. Lowinski, acting president of the Des Plaines, Ill.-based Window & Door Manufacturers Association.

Aside from cost, there have been hurdles in manufacturing. Unlike a boat hull, where fiberglass is sprayed into a mold, windows can't be built in the same way. Instead, to make a window frame, fiberglass strands actually have to be pulled, or "pultruded," through a die to achieve a desired shape. The intricacies of a frame's slots, grooves, and gaps make the process more complex. "It's like pulling taffy out of a tube," Lowinski says. "There are just a number of issues that have to be overcome."

Disputes over who "owned" pultrusion technology in the 1980s also slowed fiberglass' rollout in the United States. In Canada, though, where extreme winters demand highly efficient windows, fiberglass has been used for decades. Manufacturers such as InLine Fiberglass, FiberTec, Duxton, and OmniGlass all hail from north of the border. "In Canada, fiberglass windows are like vinyl windows in the United States," says Schmotzer. "It's recognized in Canada as an excellent window material choice much more often."

That gap is closing, though. In the United States, Milgard started offering its WoodClad line of fiberglass windows in 1990. By 1996, Marvin joined the game with its Integrity product. Then, in 2003, Pella launched Impervia. Even industry giant Andersen, which doesn't explicitly market a fiberglass window, is widely cited for its use of fiberglass components.

"The key players in the business are starting to realize that if they want to be in the right spot long term, they need to have a presence in pultruded fiberglass," says Al Dueck, president of Duxton Windows & Doors of Winnipeg, Manitoba, which specializes in fiberglass.

"Clearly, as we look at the marketplace, the area where the most growth is occurring is fiberglass," says Duane Putz, director of sales and marketing for Pella's advanced materials division. "It's a good alternative, not only to the wood and vinyl products that Pella carries, but to other products in the marketplace, namely, aluminum."

"When it comes to fiberglass, the sky's the limit," agrees John Kirchner, a spokesman for Marvin Windows and Doors.

Installation Challenges

If fiberglass does start commanding a bigger piece of the window market, builders, remodelers, and dealers will need to adjust to its unique installation challenges, as well as its business model.

"There is a transition for installers to go through," says Schmotzer. "For one, you can't bow fiberglass. Sometimes, you can cheat on a vinyl window and bow it a little bit to get it in, but you can't do that here. You have to be very precise."

Then, there's the weight issue. "If you have the same sized vinyl and fiberglass window, the fiberglass is going to be a lot heavier," says Schmotzer. "You can't move as fast."

Margins also can be an issue. Schmotzer says that while the Comfort Line fiberglass windows he carries are a higher-end product than his vinyl and aluminum offerings, they're not necessarily more profitable. "Due to fiberglass being more expensive to manufacture, you still have to be competitive in the marketplace," Schmotzer says. "So, even though it's a premier product, we don't have a higher markup on our fiberglass windows."

Yet, for all the hurdles fiberglass still may have, Schmotzer and others see it as the way of the future, not just for windows, but for many building products. "Demand for fiberglass in the marketplace is just in its infancy," Schmotzer says. "Long term, I wouldn't be surprised if you eventually saw fiberglass 2x4s."


Omniglass. The firm, which has been producing fiberglass windows since 1983, targets its Fibertherm window system for renovation and new construction. Offerings include casement, awning, slider, picture, bay, and bow windows. The firm's standard colors are white and bronze, but it can produce any custom color. 204-987-8522.