How much does it cost to install a fiberglass window?

National Average Range:
$6,750 - $11,000

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Updated: December 13, 2023

Reviewed by Adam Graham remodeling expert. Written by

To provide you with the most accurate and up-to-date cost figures, we gather information from a variety of pricing databases, licensed contractors, and industry experts.

With its ability to look like real wood combined with superior insulating capabilities, fiberglass is becoming the most popular option for windows and doors with homeowners and contractors. Fiberglass windows are manufactured using fibers and resin, creating a much stronger window frame than wood or vinyl while providing superior insulation. Fiberglass window frames do not expand and contract with temperature fluctuations, so they are a great window for all seasons regardless of where you live.

The national average cost range is $6,750 to $11,000, with most homeowners paying $7,500 for 10 replacement fiberglass prefab double hung, double-pane windows with low-E glass. This project’s low cost is $600 to have a handyman install one prefab single hung fiberglass replacement window with standard glass. The high cost is $18,000 for 10 custom impact-resistant fiberglass windows with spectrally selective coating and krypton-filled glass.

Fiberglass Window Prices

Fiberglass Window Costs
National average cost$7,500
Average range$6,750 - $11,000

Prefab vs Custom Fiberglass Windows Cost

Fiberglass windows are readymade and available in many sizes and types. However, there may be times when you have an oddly sized window or require a specific shape or color. In these instances, you may need to purchase a custom window. Custom windows are made to order, so they take longer to receive and cost more than prefab windows. In most situations, a prefab window likely works best for your home. However, in older homes and unique situations, a custom window can fit better. For example, oversized arch windows and some large garden windows and windows in colors other than white may need to be custom.

Pricing for custom windows can be difficult to predict. Because the windows are made to order, they can have a wide range of costs 30% to 100% higher than a prefab window. Below are the average costs for an installed single prefab and custom double hung window.

Comparison of the cost to install a prefab and a custom fiberglass window (mobile)

Window TypeAverage Costs (Installed)
Prefab$675 - $1,100
Custom$890 - $2,200

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Fiberglass Window Prices by Size

Fiberglass windows come in many sizes. Some windows come in set sizes classified as small, average, or large-sized windows. For example, a small window can be an awning, transom, or a below-average sized sash window. Small windows are often found in basements, bathrooms, and above or next to larger windows for more light. For example, you may have an awning window above a larger fixed window to let in air.

Average-sized windows include most sash windows, casement windows, smaller sliders, egress windows, and some picture windows. Average-sized windows are found in kitchens, living rooms, and bedrooms.

Large windows are typically the most expensive and include bay windows, picture windows, some large sliders, some arched windows, and many garden windows. These windows are most commonly found in living rooms and stairwells, but they can also be found in some bedrooms. Below are the average costs for differently sized replacement fiberglass windows without installation.

Material cost of a small, average, and large prefab and custom fiberglass window (mobile)

Window SizePrefab Cost (Materials Only)Custom Cost (Materials Only)
Small$200 - $1,000$260 - $2,000
Average$300 - $1,800$390 - $3,600
Large$400 - $3,200$520 - $6,400

Fiberglass Window Cost by Type

There are many fiberglass windows to consider, and the type can impact your project’s final costs. Some windows are basic and cannot be opened, such as fixed windows. Other types are more elaborate and open differently, resulting in higher costs. The more elaborate the window, the higher its costs. Below are the average costs for various types of prefab and custom fiberglass windows.

Material cost of a prefab and custom fiberglass window by type: transom, egress, single hung, awning, double hung… (mobile)

Window TypePrefab Costs (Materials Only)Custom Costs (Materials Only)
Transom$200 - $350$260 - $700
Egress$200 - $800$850 - $1,500
Single Hung$200 - $1,500$260 - $3,000
Awning$240 - $2,000$315 - $4,000
Double Hung$250 - $2,000$325 - $4,000
Picture$280 - $2,700$365 - $5,400
Arched$300 - $1,100$390 - $2,200
Casement$300 - $2,125$390 - $4,250
Sliding$300 - $2,300$390 - $4,600
Bay$400 - $2,400$520 - $4,800
Garden$600 - $2,200$780 - $4,400


Transom fiberglass windows are $200 to $350 each for a prefab window. The cost of a custom transom window is $260 to $700 each. Transom windows are usually installed above another window or doorway, but they can be installed in basements. They are designed to let air and moisture out of a space. Fiberglass works well in areas that need ventilation due to humidity, such as a bathroom because it is not impacted by high humidity.


Egress fiberglass windows cost $200 to $800 for prefab windows. Custom fiberglass egress windows cost $850 to $1,500. Technically, any window that can admit an adult person’s body is considered an egress window. This means the window could be used as an exit in a fire or emergency. Fiberglass windows are not affected by extreme heat and do not melt in a blaze like a vinyl window or burn like wood. This makes them good for egress windows in areas prone to wildfires.

Single Hung

The cost of a single hung fiberglass window is $200 to $1,500 for prefab. The cost of a custom fiberglass single hung window is $260 to $3,000. Single hung windows are a subtype of sash windows. Only the bottom half operates, sliding up and down to provide ventilation, while the top pain remains fixed. Fiberglass window frames do not swell in humidity like wood or warp like vinyl. This means sash windows are more likely to remain operational at all times with ease when you choose fiberglass.


Fiberglass awning windows cost $240 to $2,000 for prefab windows. The cost of a custom window is $315 to $4,000. An awning window is typically installed above another window but may be used alone. They open outward from the bottom to let air in and let humidity out. They cannot be used for egress. Fiberglass makes a good choice for these windows in areas with high humidity because the material is unaffected by moisture and the frame does not swell.

Double Hung

The cost of a prefab double hung fiberglass window is $250 to $2,000. The cost of a custom fiberglass double hung window is $325 to $4,000. Double hung windows are another sash window. The upper and lower portions of the window move independently in this window. This gives you greater opportunity for ventilation or egress. Double hung windows are common in older homes because fiberglass windows can give you the look of wood to match these homes while providing the strength and insulation of fiberglass.


A prefab fiberglass picture window costs $280 to $2,700. The cost of a custom fiberglass picture window is $365 to $5,400. Picture windows are large fixed windows with a single glass pane framing the view as a picture. They are common in living rooms, bedrooms, and other areas with a nice view. Fiberglass is good for large picture windows because of the frame’s strength.


A prefab arched fiberglass window costs $300 to $1,100. The cost of a custom arched fiberglass window is $390 to $2,200. Arched windows are fixed windows with a square bottom and an arch at the top. They are generally positioned over other windows or doors to provide more light and decoration. When using a large arched window, fiberglass makes a good choice for the frame because of its strength and durability.


A prefab fiberglass casement window costs $300 to $2,125. The cost of a custom fiberglass casement window is $390 to $4,250. Casement windows are tall narrow windows that open outward. They can operate by pushing or turning a crank. They come in many styles and sizes and can be installed singly or in pairs. They often offer more ventilation than a sash window.

Fiberglass Sliding Window

The cost of a prefab fiberglass sliding window is $300 to $2,300. The cost of a custom fiberglass sliding window is $390 to $4,600. Sliding windows are large windows that open horizontally. One or both sides may open by sliding along a track. These windows may be made of a single large glass pane on each side or broken into smaller panels. This is a good window for areas where you want light and an operational window.


A bay fiberglass prefab window costs $400 to $2,400. The cost of a custom fiberglass bay window is $520 to $4,800. Bay windows are made of three sections - a large fixed window in the center with smaller operational windows on each side. The three windows meet at 45º angles, making the window extend out slightly and providing more room inside. Depending on the window size, fiberglass can be a good choice for the frame because of its strength and ability to hold large windows without warping.


A prefab fiberglass garden window costs $600 to $2,200. The cost of a custom fiberglass garden window is $780 to $4,400. Garden windows are designed to protrude from your home on the top, bottom, and sides. This creates a small box for an indoor garden. These windows come in many sizes. They use more glass than other windows, so they cost more. The frame is around the section attached to the home, so it does not impact the cost as much.

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Fiberglass Window Cost by Type of Pane

You also have several choices for the glass type in the frame. Some windows are available with a single glass pane, which are simple and affordable but do not provide much insulation. You can also use windows with two or three glass panes, known as double-pane and triple-pane windows, which carry more insulation. These can be filled with argon or krypton gas, further insulating the window.

You can also use different coatings on the glass. Low-E coating is most common in northern states because it blocks UV rays without blocking heat. You can also choose a spectrally selective glass in hot climates to block UV rays and heat from entering.

Finally, you can also have laminated glass to prevent the glass from shattering. Impact-resistant glass is heat-treated, laminated for strength, and recommended in areas with hurricanes and high winds.

Most manufacturers have prefab windows with different glass types available. Because custom windows are made to order, you need to contact the manufacturer to get accurate pricing on the glass types with the window you want. Below are the average costs for a prefab double hung fiberglass window with the various glass types.

Cost of a prefab fiberglass window by type of pane: single-pane, double-pane, low-e, spectrally selective coating… (mobile)

TypeAverage Prefab Cost (Materials Only)
Single-Pane$200 - $500
Double-Pane$250 - $800
Low-E$350 - $1,250
Spectrally Selective Coating$375 - $1,850
Argon-Filled$400 - $1,900
Triple-Pane$450 - $1,950
Krypton-Filled$650 - $2,500

Fiberglass Window Prices by Brand

Many reputable companies make fiberglass windows. Some companies specialize in specific things like energy efficiency, while others focus more on value. Pella and Andersen are two of the most well-known brands for windows, and both make a selection of fiberglass window options. These include windows designed for strength, durability, and energy efficiency. Both companies have affordable and high-end lines of fiberglass windows.

Milgard Windows and Doors is most known for vinyl windows, but they carry a single line of fiberglass windows. Their focus is on low-maintenance window materials, and their line of fiberglass windows is available in many styles.

Inline and Marvin offer many options for fiberglass windows. Inline windows are generally considered high-end and have several designer choices and styles. Marvin’s windows are also considered a high-end option to enhance the home’s appearance and efficiency.

Below are the average costs for a double hung fiberglass prefab window from each company. Not all companies offer custom pricing, and costs for custom windows can fluctuate. Contact the manufacturer directly if you are interested in custom windows.

Cost of a Pella, Milgard, Inline, Andersen, and Marvin fiberglass window (mobile)

BrandAverage Costs (Materials Only)
Pella$400 - $2,000
Milgard$500 - $1,750
Inline$600 - $2,000
Andersen$600 - $2,300
Marvin$800 - $1,600

Fiberglass Replacement Windows Cost

Fiberglass windows are popular for replacement windows. They are incredibly strong, durable, and low maintenance. They work well in all climates and insulate better than some other window frame materials. This makes them common in replacement situations.

It is common to replace windows in homes when they get old, sticky, are difficult to open, or when they are poorly insulating and you want to lower your energy bills. The average labor cost to install a fiberglass replacement window in your home ranges from $100 to $300. This typically includes removing the old windows and installing the new ones. Generally, costs for replacement are lower than costs for installing a new window because the frame and window opening are already there.

Replacing multiple windows at once can help lower the labor cost per window. The more windows installed at once, the lower the labor cost per window because travel and setup costs can be lowered. Below is the average labor cost to replace windows of varying quantities.

Labor cost per window to replace 1-4, 5-9, 10-19, and 20+ fiberglass windows (mobile)

QuantityAverage Labor Costs
1 - 4 Windows$100 - $300
5 - 9 Windows$90 - $280
10 - 19 Windows$85 - $265
20 + Windows$80 - $240

Replace All Fiberglass Windows in a Home

Most homes have 22 windows of varying types. Smaller homes may have as few as 15 windows, while larger homes may have as many as 30. For this reason, you can likely get the best costs by replacing all of them rather than piecemeal if you consider replacing your windows. Your labor costs per window are likely lower, and some retailers also give you a better cost on the windows if you purchase multiple. Below are the average costs to replace all the windows in an average home, with fiberglass windows assuming a mixture of the most common types.

Cost to replace 15, 20, 25, and 30 fiberglass windows in a home (mobile)

Number of WindowsAverage Cost (Installed)
15 Windows$10,125 - $12,750
20 Windows$13,000 - $17,000
25 Windows$16,250 - $21,250
30 Windows$19,500 - $25,500

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Cost to Install a Fiberglass Window in an Existing Wall

If you have an existing wall in your home without a window, you can add one. This is a bigger project than replacing a current window and has higher costs. The siding must be removed, and a hole cut into the wall before the window can be framed. The window is installed, and then new trim needs to be added, and the window finished. This is a bigger project with higher material costs because replacement windows use the existing frame and casing. The labor fees cost $500 to $1,500 for a total range of $1,100 to $3,200 to add a new fiberglass window to an existing wall.

Cost to Add a Fiberglass Window to New Construction

Costs in new construction are also higher than for replacement windows but lower than adding a window to an existing wall. In new construction, the window is framed with the wall. Once the window has been installed, the interior and exterior can be finished with the walls, so there are no additional costs like in a new window addition. Adding a window in new construction costs $125 to $1,400 per window in labor plus the cost of the window for a total range of $550 to $2,500 for a new fiberglass window.

Fiberglass Window Insulation Cost

Properly insulating a fiberglass window prevents debris, such as dirt and water, from entering. It also keeps air from coming into the house through cracks during the winter. Fiberglass windows have great insulation properties. They are manufactured using fibers and resin, two materials that do not expand or contract with temperature changes. This makes them a good insulation window for all seasons. Around the window, a contractor uses an insulation film to ensure there are no cracks between the window and the house. Window insulation film costs $30 to $60 per window, including materials used. You can also hire a professional to install a special insulation foam in and around the frame, with costs ranging from $50 to $300, not including materials.

Kitchen sink next to new sash windows

Fiberglass Windows Pros and Cons

Fiberglass windows have become one of the most popular materials for windows and doors. It is very strong and durable, holding up much longer than other window frames. A fiberglass window can last 50 years or more, even in climates with high winds and storms.

Fiberglass is also a good insulator. Combined with a double-pane or other energy-efficient glass, a fiberglass window can help prevent thermal transfer, making your home more comfortable and lowering energy bills.

Fiberglass can also mimic wood with a natural wood grain. It does not need to be painted, but you can paint it to change its color.

The biggest drawbacks are availability and cost. Some companies make only limited lines in fiberglass and produce more windows in vinyl or wood. This may change as fiberglass becomes more common, but it may limit your options now, depending on the company. It can also be more expensive than aluminum and vinyl and rivals wood in some high-end windows. This makes it expensive if you plan to replace multiple windows.

Vinyl vs Fiberglass Windows Cost

Vinyl and fiberglass make good replacement windows. Both are low-maintenance options that can help insulate the window frame. Fiberglass is the more durable option because vinyl can be impacted by extreme heat and cold - warping in the former and becoming brittle and cracking in the latter.

Vinyl windows have a smooth surface frame and a softer finish. Fiberglass windows look closer to wood and may have a simulated wood grain for some windows. Both are most common in white but can be found in other finishes.

Fiberglass windows last longer than vinyl - 50 years for fiberglass, while vinyl lasts about 30 years. They are also slightly more expensive than vinyl, but both materials are less expensive than wood. Below are the average costs for installing 10 replacement double hung windows using both materials.

Comparison of the cost to install vinyl and fiberglass windows (mobile)

Window MaterialAverage Costs (Installed)
Vinyl$6,500 - $9,500
Fiberglass$6,750 - $11,000

Fiberglass vs Wood Windows Cost

One of the benefits of fiberglass windows is they can resemble wood. Natural wood windows are popular in older and historic homes and those who want a good insulator for their window frame. Fiberglass is also a good insulator and can resemble wood but is much lower maintenance than wood while also stronger. Wood frames are impacted by humidity. They swell and shrink with the moisture in the air. This can make them stick or be difficult to open. It can also cause paint or stain to crack, so they need frequent painting to look their best. Fiberglass windows are not impacted by moisture, do not swell or shrink, and are virtually maintenance-free.

Wood windows also cost considerably more than fiberglass windows, making fiberglass an increasingly popular choice. Below are the average costs to install 10 replacement windows of both types.

Comparison of the cost to install fiberglass and wood windows (mobile)

Window MaterialAverage Costs (Installed)
Fiberglass$6,750 - $11,000
Wood$7,500 - $14,000

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Enhancement and Improvement Costs

Outdoor Frame Painting

Unless you opt for a dual-color window frame, the frame’s color on the exterior is usually the same as the interior - white, in most cases. You can paint it to match the trim on your home if you want. The cost to paint trim is $1,000 to $3,000, and it is best to paint the trim and frames together for the best results.

Window Screens

Window screens let you open your windows and enjoy fresh air without worrying about bugs. Costs for window screens average $70 to $200, depending on the type and style.

Additional Considerations and Costs

  • Colors. Fiberglass windows can be powder coated in a range of colors. These colors and costs vary depending on the company. Some do not charge extra for a single color. Some also offer dual-color windows, which have a different color on the exterior. Dual-color windows may increase the project’s cost.
  • Lifespan. Due to the properties of a fiberglass window, expect them to last for up to 50 years.
  • Energy efficiency. Fiberglass windows are a great option for energy efficiency. The glass fibers do not expand, contract, or conduct heat or cold. The frames are also energy-efficient compared to aluminum and vinyl.
  • Flame retardance. In a fire, fiberglass windows have self-extinguishing properties that prevent them from emitting toxic fumes.
  • Eco-friendly. Fiberglass windows are an eco-friendly choice due to their insulating properties. They help prevent heat loss, so you may not need as much gas or electricity for heating.
  • Quotes. Get several quotes when looking for fiberglass windows to ensure you are getting the best value because material prices vary. Labor costs also vary depending on who you contact.
  • Timing. Get pricing to install fiberglass windows during a contractor’s down season. This is usually during the late fall and early winter. You may receive considerable discounts during this time.
  • Maintenance. Fiberglass windows are virtually maintenance-free. They do not peel or fade and only need to be cleaned with a damp cloth.
  • Location. The location of the window in your home can influence costs. Different spaces have varying window needs, impacting your window size and type and project cost.


  • What are the disadvantages of fiberglass windows?

There are very few disadvantages to a fiberglass window. Some companies may not offer as many options for fiberglass, which can be a potential drawback. They can also be more costly than vinyl and aluminum windows.

  • Are fiberglass windows more expensive than vinyl?

Yes, fiberglass windows are more expensive than vinyl. While vinyl has starting costs of around $650 per window installed, fiberglass costs $675 per window installed.

  • What is a fiberglass window?

Fiberglass windows are windows composed of fibers and resin, materials that do not expand or contract with temperature fluctuations. Fiberglass windows are popular due to their many benefits. They increase thermal performance by lowering your energy bills and provide strength, durability, and a beautiful appearance.

  • Are fiberglass windows better than wood?

This depends on your needs and preferences because wooden and fiberglass windows have advantages. Many people find wooden windows more attractive, but fiberglass windows last longer and require less maintenance.

  • Do fiberglass windows fade?

No, fiberglass does not fade. The color is bonded with the material, giving it a long lifespan.

  • Are fiberglass windows energy-efficient?

Yes, fiberglass windows are rated as some of the most energy-efficient windows. They have strong insulating properties and can help keep heat inside the home.