Fiberglass Windows

Fiberglass is quickly becoming the replacement windows material of choice because of its unique advantages that it has over other kinds of windows. Living in, you’re probably looking for a window that doesn’t give into the wear and tear of weather over time. This is the perfect material for you.

Fiberglass windows are manufactured from shaped and molded sheets of glass fibers, which allow for excellent molding characteristics, in addition to high tensile strength. This makes it excellent choice for homeowners looking for a durable window that will last a long time.

Benefits of Fiberglass Windows Insulation

Fiberglass is the best insulating material made into windows today. It is made from a simple polymer that is reinforced with thin strands of pulled glass. Air is trapped inside, and it makes for the best insulation of any window type. It also will not conduct heat or cold, so that its temperature should be neutral to the touch. Fiberglass is suitable for any climactic area and any temperature.

Strength and Durability

Fiberglass windows are very strong and durable with a high strength–to–weight ratio. Fiberglass windows provide eight times greater strength than vinyl windows.

  • Fiberglass, unlike vinyl, wood and metal will not warp, crack, rot or bow. Its high tensile strength resists warping and twisting.
  • Fiberglass expands and contracts at similar rate as glass. This means there is less stress between the glass and frame which gives them a better fit, reduces air leakage and provides stability over temperature extremes. It is an extremely durable substance and will not succumb to temperature swings, moisture, structural damage or other types of abuse.
  • Fiberglass is inherently chemical-resistant: stands up to corrosive effects of salt, chemicals and atmospheric pollutants: Good for seacoast or industrial environments.
  • It has a high resistance to deterioration: resist to UV rays, moisture, rot, oxidation and rust, insects and woodpeckers.
  • The window apart from the glass will require almost zero maintenance.


The structure and nature of fiberglass windows is such that while being an excellent temperature insulator, it is also a great sound insulator. This means that with your windows closed and the appropriate glass in place, you will not be subjected to loud sounds outside your home.


Because the insulation of fiberglass is so effective, and because the temperature outside will not warm or cool the actual fiberglass in the window itself, excess condensation will not form in your home in any weather.


  • nlike, vinyl, for a custom look, pultruded fiberglass windows can be painted to match your exterior interior paint or painted at the factory with a baked-on finish that won’t peel.
  • Gives you the aesthetic look of a wood window with the durability of fiberglass. Not “plastic” like some vinyl framed windows.
  • The profile of a fiberglass window is much narrower than vinyl or wood framed windows. This provides more glass area giving your home better views and more natural light.
  • The strength of fiberglass enables homeowners the ability to design large window units with thinner frames without reinforcing. This is especially help full with large projects such as sun rooms and other glass enclosures.

“Siding and Windows Group did a fantastic job! They replaced our dark brown Tudor with bright Hardie Board to create the Crafstman style I envisioned. We also used them for all our windows, exterior doors, fascia, soffit, and gutters. They are extremely responsive and stuck to their timeline. They also use a very helpful rendering software to help you picture your design, which I loved. I would definitely recommend!”

-Sara R.

Energy Costs

  • For all these reasons and more, the most important benefit you will gain from having fiberglass windows is the savings from energy bills. It is estimated that on average, the difference in energy costs between fiberglass windows and any other type of window is 20 – 40%.
  • A fiberglass window has both its advantages and its disadvantages. Before you go to pick out your window, you need to know what you are buying to see if fiberglass windows best meet all your needs. You need to know its strength and durability, cost, and maintenance.

Strength & Durability

  • Fiberglass windows are very strong and durable with a high strength – to – weight ratio. Fiberglass windows provide eight times greater strength than vinyl windows. In comparison to other materials, fiberglass has the highest resistance to rotting, warping, and twisting and the window’s frame and sash corners will not separate or crack. Also, fiberglass will not corrode.


  • Fiberglass windows are considered a more upscale replacement window. For fiberglass, the cost of the window and installation of a basic model is on average $311-378 dollars, while a premium quality fiberglass window and installation are around $429-507. These estimates do not include costs for framing the rough opening, interior trim molding, and decorative fittings. Note that all of these prices will vary depending on your location because labor costs across US vary. These prices will also vary depending on the size of the window, type of glass and other accessories.


  • One of the biggest benefits of fiberglass windows are virtually maintenance-free. You can repaint them a different color if you choose to go for a different look. This means that if you ever decide to replace siding on your house, you will easily be able to repaint fiberglass windows to match it. If you prefer the indoor look of natural wood, it is possible to order fiberglass frames with wood finishes.

Fiberglass Window Products

When fiberglass windows are required, Quality Roofing Siding and Windows prefers to use products from Marvin Essential Casement collection.

Essential Casement by Marvin

All Essential Casement windows and doors feature Ultrex construction inside and out. Beautiful, easy to use and as low-maintenance as a material can get, Ultrex® provides exceptional aesthetics, outstanding durability, and standard ENERGY STAR-qualified performance. Six exterior finishes combine with pultruded fiberglass construction to offer virtually indestructible exteriors, while the low-maintenance classic white profiled interiors provide a beautiful classic appearance.

Benefits of Siding Replacement

  • Line of fiberglass windows and doors in both standard and special sizes
  • Standard glazing is dual pane: two panes of glass with Low E coatings and argon insulating gas
  • Low-maintenance, high-durability Ultrex exterior and interior
  • Stone White, Pebble Gray, Cashmere, Bronze, Evergreen and Ebony exterior finish options, or paint with no adverse effect on durability
  • Lite patterns and factory mulling allows you to easily create custom looks

What is Ultrex?

Durable, low-maintenance, strong, stable and tough: Everything you want your home to be, and everything that Ultrex delivers.

Ultrex is Marvin’s proprietary creation made of pultruded fiberglass. Thin, strong cables of glass are saturated with special resin compounds, creating a remarkably durable material that vastly outperforms vinyl and roll-form aluminum. Because of its glass components, Ultrex has an extremely low thermal expansion rate; what little effect heat and cold has on it is matched by the glass in your window. So your double hung, glider or other Integrity unit remains tightly sealed without leaks, seal failures or stress cracks to diminish the unit’s long-term performance and energy efficiency.

Their patented finishing process mechanically bonds an impermeable acrylic cap onto the already virtually indestructible surface. This acrylic cap bonds to the pultruded fiberglass during curing and is up to three times thicker than our competitors’ finishes, providing better adhesion and resistance to scratches, marring and dings. Fading is prevented thanks to this superior patented finishing process which resists UV degradation, with five times more UV resistance than vinyl; This eliminates fading, chalking and streaking while allowing Integrity to offer darker finishes, like Bronze and Ebony, with total confidence in their long-term performance.