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Pultruded Windows:Characteristics, Types, Forms, and Properties

Pultruded windows are a type of window manufactured using the pultrusion process. This process involves mixing fiber materials (usually fiberglass) with resin and pulling them through a heated mold to form rigid linear profiles. These profiles are then cut to the desired lengths and assembled into window frames. Pultruded windows are widely favored for their high strength, durability, and excellent thermal performance. They are particularly suitable for residential, commercial, and harsh environmental applications. Compared to traditional window materials, pultruded windows offer significant advantages in energy efficiency, maintenance costs, and environmental friendliness.

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What are Pultruded Windows?

pultruded window

Pultruded windows are a type of window made using the pultrusion process. This manufacturing technique involves saturating fibers, typically fiberglass, in a resin mixture to create linear materials. The process involves pulling fiber-reinforced resin through a heated die, which solidifies into a hard linear profile. These profiles are then cut to length and assembled into window frames.

What Is the Other Term for Pultruded Windows?

Pultruded windows are also commonly known as fiberglass windows. This term is used because the pultrusion process primarily involves the use of fiberglass, which is a type of fiber-reinforced plastic (FRP) or glass-reinforced plastic (GRP).

How Are Pultruded Windows Made?

Pultruded windows are made through a continuous process called pultrusion. Here are the key steps involved in the manufacturing of pultruded fiberglass windows:

1. Fiber Reinforcement Preparation

Continuous rovings or mats of reinforcing fibers, usually fiberglass, are drawn from creels and guided into position. The fiber reinforcements are carefully arranged according to the structural requirements of the final window profile.

2. Resin Impregnation

The fiber reinforcements pass through a resin bath or impregnator, where they are saturated with a thermosetting resin, such as polyurethane, polyester, or vinyl ester resin. The resin fully wets and coats the fibers.

3. Preforming

After impregnation, the resin-saturated fibers enter a preforming system that organizes the material into the desired cross-sectional shape of the window profile. Excess resin is squeezed out, and additional components like surfacing veils or core materials may be added at this stage.

4. Heated Die

The preformed reinforced resin material is then pulled through a heated steel die, which finalizes the shape of the pultruded profile. The steel die is precisely machined to the dimensions required for the window frame components.

5. Curing

As the material passes through the heated die, the thermosetting resin undergoes a curing reaction, solidifying and hardening into a rigid, high-strength fiber-reinforced polymer (FRP) profile.

6. Pulling

A continuous pulling system, typically using reciprocating pullers or a caterpillar pull system, applies consistent pulling force to draw the material through the die.

7. Cutting

After emerging from the die, the pultruded profile is cut to the required lengths using saws or other cutting methods.

8. Post-Processing

The cut pultruded window profiles may undergo additional processing steps such as drilling, mitering, joining, coating, or surface finishing to create the final window frame components.

What Are Different Types of Pultruded Windows?

Pultruded windows come in various types, each designed to meet specific needs and preferences. Here are some different types of pultruded windows:

1. All-Fiberglass Windows

These windows are entirely made of pultruded fiberglass, known for their high strength, durability, and low maintenance. They offer excellent thermal performance and weather resistance, making them ideal for both residential and commercial applications.

2. Fiberglass-Clad Wood Windows

These windows feature a wood interior and a fiberglass exterior. The wood provides a warm, traditional appearance indoors, while the fiberglass exterior offers superior durability and weather resistance. This combination allows homeowners to enjoy the aesthetic benefits of wood without the high maintenance requirements.

3. Hybrid Windows

Hybrid windows combine different materials to leverage the strengths of each. For example, some windows feature fiberglass sashes with composite frames made of wood and vinyl. These windows balance durability, thermal performance, and cost.

4. Fiberglass Casement Windows

Casement windows are hinged on the side and open outward like a door. Pultruded fiberglass casement windows are known for their good ventilation, easy cleaning, and excellent air and water tightness. They are often used where maximum ventilation is desired.

5. Fiberglass Awning Windows

Awning windows are hinged at the top and open outward. They are typically used in combination with other window types or placed higher on walls to provide ventilation while maintaining privacy. Pultruded fiberglass awning windows offer the same durability and thermal efficiency as other fiberglass windows.

6. Fiberglass Double-Hung Windows

Double-hung windows have two sashes that slide vertically. Pultruded fiberglass double-hung windows are popular for their classic appearance and ease of cleaning, as both sashes can tilt inward.

7. Fiberglass Picture Windows

Picture windows are large fixed windows that do not open. They are designed to provide an unobstructed view and allow maximum natural light to enter. Pultruded fiberglass picture windows are strong enough to support large glass panes without warping or bending.

8. Fiberglass Sliding Windows

Sliding windows have one or more sashes that slide horizontally. Pultruded fiberglass sliding windows are easy to operate and offer a sleek, modern look. They are often used in spaces where casement windows are impractical.

9. Fiberglass Bay and Bow Windows

Bay and bow windows extend outward from the building, creating additional interior space and panoramic views. Pultruded fiberglass bay and bow windows are robust enough to support the extended structure while offering excellent thermal performance.

10. Custom and Specialty Fiberglass Windows

Manufacturers can create custom shapes and sizes using the pultrusion process, including arched, circular, and other specialty windows. This flexibility allows for unique architectural designs and applications.

What Are the Components of Pultruded Windows?

Pultruded windows consist of several key components, each contributing to their overall performance, durability, and efficiency. Here are the main components involved in the manufacturing of pultruded windows:

1. Fiber Reinforcement

The primary structural component of pultruded windows is the fiber reinforcement, usually made of fiberglass. These fibers provide the tensile strength and stiffness required for the window frame. The fibers come in various forms, such as continuous rovings, mats, or fabrics.

2. Resin Matrix

The fibers are impregnated with a resin matrix that binds them together and provides additional strength and durability. Common resins used in pultruded windows include polyester and polyurethane.

3. Additives and Fillers

Various additives and fillers are incorporated into the resin matrix to enhance specific properties of the pultruded profiles. These include:

  • Pigments: Provide color and UV resistance.
  • Fillers: Improve mechanical properties and reduce cost.
  • Catalysts: Promote the curing process of the resin.

4. Surface Veils

Polyester-based surface veils are often used to improve the surface finish and protect the fibers from environmental exposure. They also provide a smooth, uniform surface, enhancing the aesthetic appeal of the window frames.

5. Insulating Materials

Pultruded window frames typically have hollow sections that can be filled with insulating materials to enhance thermal performance. This helps reduce heat transfer and improves the energy efficiency of the windows.

6. Coatings and Finishes

The exterior surfaces of pultruded windows are usually coated with durable finishes to protect against weathering, UV radiation, and other environmental factors. These coatings can include:

  • Powder Coatings
  • Paints
  • UV-resistant coatings

7. Seals and Gaskets

To ensure airtightness and water resistance, pultruded windows are equipped with seals and gaskets. These components help prevent air and water infiltration, enhancing the overall energy efficiency and durability of the windows.

8. Glazing Units

The glazing used in pultruded windows can vary based on specific application and performance requirements. Common types include:

  • Single glazing
  • Double glazing
  • Triple glazing
  • Low-emissivity (Low-E) glass
  • Argon or krypton-filled glass units

9. Hardware

Hardware components such as locks, handles, and hinges are crucial for the functionality and security of the windows. These parts are typically made of materials that complement the durability and strength of the pultruded window frames.

What Are the Advantages of Pultruded Windows?

Pultruded windows offer numerous advantages over traditional window materials like wood, aluminum, and PVC. These benefits arise from the unique properties of pultruded fiberglass materials and the pultrusion manufacturing process. Here are the key advantages:

1. High Strength and Durability

Pultruded fiberglass windows are known for their exceptional strength and durability. The combination of fiberglass and resin matrix results in a material that is strong, lightweight, and impact-resistant. This makes pultruded fiberglass windows highly durable and capable of withstanding harsh environmental conditions without warping, cracking, or corroding.

2. Low Thermal Conductivity

One of the most significant advantages of pultruded fiberglass windows is their low thermal conductivity. Pultruded fiberglass offers better insulation compared to traditional materials like aluminum, reducing heat transfer and enhancing energy efficiency. This results in lower heating and cooling costs for buildings.

3. Dimensional Stability

Pultruded fiberglass has a very low coefficient of thermal expansion, meaning it expands and contracts very little with temperature changes. This stability ensures that windows remain tightly sealed, preventing gaps and leaks over time, thus improving thermal performance and longevity.

4. Corrosion and Weather Resistance

Pultruded windows are highly resistant to corrosion, moisture, and UV radiation. Unlike wood, they do not rot, and unlike metal, they do not corrode. This makes pultruded windows ideal for use in high-humidity areas, coastal regions,

and extreme weather conditions.

5. Low Maintenance

Pultruded fiberglass windows require minimal maintenance compared to wood or metal windows. They do not need regular painting, staining, or sealing and are easy to clean. This low maintenance characteristic makes pultruded fiberglass windows a cost-effective choice in the long run.

6. Design Flexibility

The pultrusion process allows for the production of complex shapes and profiles, enabling a wide range of window sizes, colors, and styles. This flexibility allows architects and designers to meet specific aesthetic and functional requirements, including curved and custom-shaped windows.

7. Environmental Benefits

Pultruded fiberglass is an environmentally friendly material. It is primarily made from sustainable resources like silica sand and consumes less energy during the manufacturing process compared to materials like aluminum and PVC. Additionally, pultruded fiberglass windows can be recycled at the end of their life cycle.

8. Energy Efficiency

Due to their excellent insulating properties and tight sealing, pultruded windows significantly improve the energy efficiency of buildings. They help reduce heating and cooling energy consumption, resulting in lower utility bills and a reduced carbon footprint.

9. High Performance in Extreme Conditions

Pultruded fiberglass windows can withstand extreme temperatures and environmental conditions without losing their structural integrity or performance. They are suitable for both hot and cold climates, maintaining indoor comfort and energy efficiency.

10. Cost-Effectiveness

While the initial cost of pultruded windows may be higher than some traditional materials, their long-term benefits, including durability, low maintenance, and energy savings, make them a cost-effective choice over the window’s lifespan.

What Are the Disadvantages of Pultruded Windows?

Despite their many advantages, pultruded fiberglass windows also have some disadvantages. Here are the main drawbacks:

1. Higher Initial Cost

One of the primary disadvantages of pultruded fiberglass windows is their higher initial cost compared to other window materials like vinyl or wood. The advanced production process and high-quality materials involved in making pultruded fiberglass windows contribute to their higher price, which may not fit everyone’s budget.

2. Limited Color and Finish Options

While pultruded fiberglass windows come in a variety of finishes and colors, the selection is typically more limited compared to vinyl or wood windows. This might make it challenging for homeowners to match the windows to their specific aesthetic preferences.

3. Difficult Repairs

If pultruded fiberglass windows are damaged, they can be more challenging and costly to repair compared to other materials. Fiberglass materials are difficult to patch, and repairs often require specialized expertise. Additionally, some manufacturers may not offer repair services for fiberglass windows, complicating the repair process.

4. Potential for Warping and Bending

Although rare, pultruded fiberglass windows can warp or bend if not installed correctly. This issue arises if the window frame is not securely attached to the wall, causing the frame to move and bend over time. Proper installation by experienced professionals and regular maintenance can help prevent this problem.

5. Fading and Discoloration

Like other window materials, pultruded fiberglass windows can fade and discolor over time when exposed to sunlight. Choosing high-quality fiberglass materials with strong resistance to fading and discoloration can minimize this issue. Homeowners can also use curtains or install window films to block UV rays and protect the windows from sun exposure.

6. Availability and Distribution

Pultruded fiberglass windows are not as widely available as other window materials. Only a limited number of companies produce these windows, and not all companies distribute them nationwide. This limited availability can make it more challenging for homeowners to find and purchase pultruded fiberglass windows.

7. Environmental Sensitivity

Fiberglass resins can turn white when exposed to UV light. Therefore, a durable factory-applied coating must be used on the exterior to protect the windows from UV damage. The thicker the coating, the better it prevents degradation caused by UV light.

What Is the Importance of Pultruded Windows in Cold Regions?

Pultruded fiberglass windows offer several important benefits in cold climates, making them an excellent choice for regions with harsh winters. Here are the key reasons why pultruded windows are well-suited for cold regions:

1. Superior Insulation Performance

Pultruded fiberglass has a very low thermal conductivity, about 800 times lower than aluminum. This means that pultruded window frames provide excellent insulation, minimizing heat transfer and preventing heat loss from the building. This insulation capability helps maintain comfortable indoor temperatures, reduces energy consumption, and lowers heating costs in cold winters.

2. Minimal Thermal Expansion and Contraction

Pultruded fiberglass has a very low coefficient of thermal expansion, almost identical to glass. This means that pultruded window frames expand and contract at nearly the same rate as the glass panes during temperature changes. This dimensional stability prevents seal failures, air leaks, and condensation issues, which are more common with other window materials like vinyl.

3. Resistance to Extreme Low Temperatures

Pultruded fiberglass windows can withstand extremely low temperatures without becoming brittle or losing structural integrity. This durability ensures that the windows maintain their performance and energy efficiency even in the harshest winter conditions, unlike some other materials that may degrade or crack in extreme cold.

4. Condensation Resistance

The low thermal conductivity of pultruded fiberglass helps maintain higher interior surface temperatures on the window frames, reducing the risk of condensation formation. This condensation resistance prevents moisture buildup, which can lead to mold growth, water damage, and other issues affecting indoor air quality and structural integrity.

5. Low Maintenance Requirements

Pultruded fiberglass windows are highly resistant to weathering, corrosion, and moisture. Unlike wood windows, they do not require regular painting, staining, or sealing. This low maintenance characteristic is especially beneficial in cold climates, where harsh winter conditions can accelerate the aging of other window materials.

6. Energy Efficiency

Pultruded fiberglass windows’ excellent insulation properties and tight sealing significantly improve the overall energy efficiency of buildings, reducing heating costs in cold climates. The long-term savings on energy bills can offset the higher initial investment in pultruded windows, making them a cost-effective choice over their lifespan.

What Is the Color of Pultruded Windows?

Pultruded windows come in a variety of colors, including standard, custom, and split finishes. These finishes are designed to be durable, UV-resistant, and low maintenance, offering both aesthetic flexibility and long-term performance.

What Are the Applications of Pultruded Windows?

Pultruded windows, made from fiberglass-reinforced polymer (FRP) through the pultrusion process, are known for their high strength, durability, thermal efficiency, and low maintenance. These unique properties make them suitable for a wide range of applications:

1. Residential Buildings

Pultruded windows are widely used in new construction and renovation of residential buildings. They are favored for their energy efficiency, durability, and low maintenance requirements, helping to reduce heating and cooling costs and making homes more energy-efficient and comfortable.

2. Commercial Buildings

In commercial buildings, pultruded windows are increasingly used for their superior thermal performance and structural integrity. They are suitable for high-rise buildings, office buildings, and other commercial structures where energy efficiency and durability are paramount.

3. Coastal and Harsh Environments

Pultruded windows are ideal for coastal regions and other harsh environments where traditional materials like wood and metal may deteriorate quickly. Their corrosion resistance, moisture resistance, and UV resistance make them suitable for buildings exposed to salt air, extreme temperatures, and high humidity.

4. Historic Renovations

Pultruded windows can be used in the restoration and renovation of historic buildings. They offer the aesthetic appeal of traditional windows while providing modern performance benefits, such as improved insulation and reduced maintenance.

5. Industrial Applications

In industrial environments, pultruded windows are suitable for facilities that require high durability, chemical resistance, and tolerance to extreme temperatures. They are used in factories, warehouses, and other industrial buildings where robust, low-maintenance windows are essential.

6. Energy-Efficient Buildings

Pultruded windows are a key component in energy-efficient and sustainable building designs. Their excellent insulation properties and low energy consumption make them suitable for buildings aiming to achieve certifications such as LEED (Leadership in Energy and Environmental Design) and Passive House standards.

7. Custom and Specialty Applications

The flexibility of the pultrusion process allows for custom and specialty window designs. Pultruded windows can be manufactured in various shapes, sizes, and colors, making them suitable for unique architectural projects and custom home designs.

8. High-Performance Buildings

Pultruded windows are used in high-performance buildings that require superior thermal and structural performance. This includes buildings in extreme climates, both hot and cold, where maintaining indoor comfort and energy efficiency is a challenge.

9. Sound Insulation

Pultruded windows, known for their excellent sealing and sound insulation properties, are used in buildings requiring high noise reduction, such as urban areas or near airports and highways. They help reduce noise pollution and enhance indoor acoustic comfort.

10. Green and Sustainable Buildings

With a long lifespan, low maintenance, and the use of sustainable materials, pultruded windows are an eco-friendly choice. They are increasingly used in green building projects that prioritize sustainability and environmental impact.

How Do Pultruded Windows Compare to Traditional Windows in Terms of Cost?

Pultruded windows, typically made from fiberglass, generally have a higher initial cost compared to traditional window materials like vinyl, aluminum, and wood. Here is a detailed cost comparison between pultruded windows and traditional windows:

Cost Comparison

Fiberglass (Pultruded) Windows

  • Average Cost: The price of fiberglass windows typically ranges from $700 to $1,400 per window. The higher price isdue to the material costs and advanced manufacturing processes involved in pultruded fiberglass.
  • Installation Cost: The installation cost for fiberglass windows is also higher, averaging around $300 per window.
  • Long-Term Value: Despite the higher initial cost, fiberglass windows are considered a better long-term investment due to their durability, low maintenance, and energy efficiency.

Vinyl Windows

  • Average Cost: Vinyl windows are the most affordable option, with prices ranging from $150 to $600 per window. They are inexpensive to produce and install.
  • Installation Cost: The installation cost for vinyl windows is about $250 per window.
  • Durability and Maintenance: While vinyl windows are low-maintenance and cost-effective, they have a shorter lifespan and may warp or discolor over time.

Aluminum Windows

  • Average Cost: Aluminum windows cost between $80 and $500 per window, making them another affordable option.
  • Installation Cost: The installation cost is relatively low, but aluminum windows have lower energy efficiency and are prone to condensation.
  • Durability: Aluminum is strong and durable but has poor insulation properties, leading to higher energy costs over time.

Wood Windows

  • Average Cost: Wood windows are among the most expensive, with prices ranging from $250 to $800 per window.
  • Installation Cost: The installation cost is high due to the need for skilled labor and potential customization.
  • Maintenance: Wood windows require regular maintenance to prevent rot and warping, adding to long-term costs.

Composite Windows

  • Average Cost: Composite windows, which can include a mix of wood, vinyl, or fiberglass, range from $400 to $1,300 per window.
  • Durability and Maintenance: Composite windows offer good durability and energy efficiency but vary significantly depending on the materials used.


  • Initial Cost: Pultruded fiberglass windows have a higher initial cost compared to vinyl and aluminum windows but are comparable or slightly higher than high-end wood and composite windows.
  • Long-Term Value: The higher initial investment in pultruded fiberglass windows is often justified by their long-term benefits, including superior durability, low maintenance, and excellent energy efficiency, leading to cost savings over their lifespan.

While the upfront cost of pultruded windows is higher, their long-term advantages make them a cost-effective choice for homeowners seeking durable, energy-efficient, and low-maintenance windows.


Pultruded windows, with their exceptional strength, durability, thermal performance, and low maintenance requirements, offer a compelling alternative to traditional window materials. Their wide range of applications, from residential to commercial and industrial buildings, along with their environmental benefits, make them a valuable investment for both new construction and renovation projects. Despite the higher initial cost, the long-term savings and performance advantages of pultruded windows make them a cost-effective choice for those looking to enhance their building’s energy efficiency and overall comfort.
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