All about fiberglass windows

We want to get many functions from our windows. People like them to let a lot of light into the room, and to keep the winter cold and the moisture and heat out of the house during the summer months. We also expect them to last decades.

Fiberglass is a product, which includes polyester resins that are activated by a catalyst and then pultruded, or pulled through a heated die. Threads of glass or glass mats are reinforced resins. Fiberglass has long been used to create reliable and ultralight materials that are also used in the production of skis, surfboards, and canoes.

Fiberglass windows (and composite windows with this material) became very popular at the beginning of a millennium. Initially, the developers tried to replace them with vinyl ones that, however, had their flaws.

The newest windows with fiberglass are completely improved by these fiberglass composites. The reason for this is that they are made of a mixture of glass fiber and polyester resins. The windows, which include fiberglass lining, are more durable and have fluctuating prices. They usually cost as much as vinyl and wood windows.

Such windows have a stronger and much more reliable structure than vinyl ones and they do not require frequent care of their owner and please the person with their beautiful appearance.

Wood is a material that does not lose its functionality for many decades, but if it is made with a poor final set, then this material can swell and contract due to temp variations, and as a result, the product’s longevity will be reduced.

Vinyl windows do not require regular maintenance, but the other components will show their properties particularly well if the manufacturer makes them into chunky profiling, which decreases the mass of glass, and it becomes less durable over the years, but that is not proof of long service life.

Fiberglass doesn’t have so many weaknesses as it is more durable and light than wooden windows, and it is also waterproof and not afraid of high or low temperatures. Even though the first varieties of this product were not so functional, modern manufacturers have improved them by adding new properties.

Back in the early part of the century, fiberglass windows were only sold in limited sizes, and also acquired a cloudy shade of sunshine and were sold only in white. In the modern world, the buyer can order individual window sizes, durable UV-blocking coatings, and choose its color and coloring, which is similar to the wood.

You can learn the features of making these windows and decide if they are suitable for your house.

What we like

  • Durable structure

  • Ability to choose a texture

  • Choice of colors

What we don't like

  • High cost

  • Manual assembly without professional assistance


What is their price? Typically, windows with fiberglass are sold at a price that exceeds the cost of vinyl or aluminum and wood by 25%.

Hand-built or professional help? The pros will help you put windows in a new house or replace the old ones. Most producers sell their products only through approved installers or dealers. But some of them sell directly to homeowners or through a network of specialized shops. To avoid leak proofing the window, we recommend that you ask for assistance in assembling a professional.

What is the period of guarantee for these products?  These windows will last you for at least a decade but they will continue to function even after that date, and when your house becomes old, these windows will still be in good condition. As for insulating glass, it has a warranty of two decades, which you will get if the seal breaks off.

How often do you have to take care of windows? Rarely, because it’s just cleaning the glass and replacing the weather-stripping every 10 years. 

wood windows

How they’re made

Fiberglass is a material in which many components are reinforced by a method such as pultrusion. This is a machine-assisted procedure that allows lengths of fiberglass roving and strand mat to be enhanced by dipping in a resin and using a heated die that strengthens the resin. (Note that a specific matrix belongs to a specific component of the product). Lineal is always smooth and rigid and it emerges from the die and is then typically cut to length. It has a special cover and implicit nylon-reinforced corner blocks. Lines and blocks can be specially deformed and then glued. This allows them to build a powerful and multi-component system.

How do you know if fiberglass windows are suitable for you?

It would fit your house in most cases because manufacturers create the most reliable and durable products at a reasonable price.


You can forget about the rain that enters your house through the unserviceable windows because these products do not allow even moisture and cold. This allows you not to worry about problems like rot, corrosion, mycosis, and swelling.

The temperature of your house will be the same. Fiberglass will be hard and strong even in the hottest and coldest months, and it will not shrink or expand. Because of this, no moisture permeates through the window.

The glass is wider and the frame is narrower. This product is very solid and thick, and it allows the manufacturer to present you with smaller windows, which will not occupy much space in the window opening, but at the same time will be inert to the wind.


Small assortment. Wood is stronger than fiberglass in that it is less convenient for custom configuration of shape and profiles, and it is represented in only one color.

It’s hard to find the manufacturers. The fact is, only some manufacturers create these windows.

UV rays can affect fiberglass resin and it becomes more chalky. You should select a window with a thick cover.

Fiberglass three ways

All Fiberglass

You have a choice of many options, each of which will fit your financial opportunities. You can choose any interior finish and even some that will remind you of the real wood due to its unique color pattern.

Wood Interior

The sills, sashes, and frames are made of fiberglass, but you will still get wooden structures in the interior of the window. This allows you to get benefits from both materials – very durable and weather-proof on the outside but still very cozy amd stylish wooden interior that you can’t get with any other material.


Windows will be able to save from 7 to 24 percent of all your energy expenses. The same is true for cooling if you live in a very hot climate. The windows will be able to save you money for air conditioning.

Improving the view

Modern fiberglass windows are no longer quite like old plain vinyl products. Factory-applied finishing covers are made from a more reliable and hard material that does not suffer from the harmful influence of UV rays. The manufacturer may even use acrylic staining in the process of the pultrusion or the assembly of the final product.

Colors. Before fiberglass products were sold only in white but today, there are different shades for both the outside and the inside of the house. You can also order color patterns  from the manufacturer that looks like wood.

Curves. The pultrusion procedure includes just straight pieces. However, some manufacturers create windows with arch-tops and curves.

Components confluence. You do not have to combine parts of the product to get a beautiful section because it is implemented as ready-to-install kits.

Energy performance. Fiberglass is the kind of material that protects your home from temperature swings. Foam and double and triple-pane glazing enrich the frame and this allows the manufacturer to make this product more efficient.

Pick your style


Wide Open

Fiberglass products will delight you with their beauty and versatility.

It has wood-lined casements and transoms that confirm what narrows all fiberglass windows’ frames. They also have such a strong side as sashes that never warp.

Seeing Green windows

Seeing Green

Such windows may be of different colors, such as grey, black, or green.  Powder covering comes with personal casements and makes double-hung windows invulnerable to UV rays.

Wall of Glass windows

Wall of Glass

These windows are quite large and they are very strong, which allows them to resist winds and precipitation. They have very solid flanking casements that can handle even the most severe storms, but the transoms product will do even better.

Beauty of bathroom Windows

Beauty of bathroom

Windows with fiberglass are very rigid in a structure that has a transom and therefore they do not allow moisture inside the design. That’s why people often choose these windows to install in the bathroom. 

Throw a Curve windows

Throw a Curve

Bow windows will make your house more spacious thanks to the sunlight. These five fiberglass casements are structured with a single faceted curve and as a result, they create a classic bow unit.

Historical Look

Three double-hung will be an excellent component for the unique gable openings of this 19th century Queen Anne. The middle arch-top will be made for the client individually and using molding.

Cost of different types of windows

Framing components are not the only thing that contributes to the process of a window renovation. Here we will describe the best varieties of windows and their common costs.

wood windows



Sliding windows look like single- or double-hung ones, but they use a horizontal rather than vertical mechanism. The most expensive type of windows amongst most common types.

Bay and Bow


A bay window includes three big panes of glass in an angled frame that extends out from the side of the house. The size of the glass allows these products to increase their price. Bow windows, by the same schema, include big panes of curved glass and cost even more.



Casement windows have hand cranks for use and rotate from left to right. The price will depend on the size of your window, a casement window with hinges will cost you a little cheaper.

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    Picture windows are what people also call fixed windows, they include a simple sheet of glass in a frame that lacks mobility. Nevertheless, picture windows are always produced in different sizes.



    A double-hung window is similar to the previous version, but it has top sashes that slide down or swing open sometimes. These windows are more premium.



    A single-hung window includes an upper pane of glass that complements the lower pane but does not have the problem of loosening. This is a cheap version of the windows and they are popular a popular option.


    Marvin Windows and Doors

     Signature Modern High-Density Fiberglass Materials

    Fiberglass windows contain strong resin, and all of this makes the windows beautiful and efficient at the same time, for example, they do not allow heat and cold. Marvin Modern product line offers you High-Density Fiberglass that will look beautiful both from the outside of the house and from the inside, as these windows are durable and have a strong aluminum layer.

    Signature Modern Awning Window Exterior View

    • High-Density Fiberglass is similar to the pultruded one in that it expands and contracts with the same intensity as glass. This allows windows to have a long lifespan.
    • These windows are durable and cannot be damaged even by the harshest weather conditions.
    • The production cycle includes proprietary frame design and makes these large sized windows strong too.

    Milgard Windows & Doors

    1. Milgard fiberglass windows will go with any interior. We also customize our production processes regularly. In this way, make windows that are best suited to each customer.
    2. We can assure buyers that Milgard windows will ensure the safety of your home and protect it from temperature changes by fiberglass, and will not be influenced by natural conditions such as storms and precipitation.
    3. Each customer will be able to rely on a particular product based on his or her financial capacity. You will be able to choose a window whose strengths will suit your purse as much as possible.
    Andersen certified contractor

    Andersen Windows & Doors

    1. Andersen fiberglass windows are very popular due to their high level of sustainability. They contain two-thirds of the content. This makes them the best choice for the modern home of any person. A-Series line of windows will satisfy any client.
    2. Also, fiberglass windows will keep your house warm and never let cold into the room. In addition, they won’t give in to bad weather conditions, so they’ll last you years and decades.
    3. Because these windows are less difficult to produce, Andersen company can offer you reasonable prices for its products.

    Simonton Windows & Doors​

    1. Simonton offers you a wide variety of products that include models like Picture Windows, Sliding Windows, and Double-Hung that will suit even the most meticulous customers. Fiberglass Ultra-Line includes suitable products.
    2. In the production of this product, we use fire-fighting components that allow windows not to be affected by hot and cold temperatures. This makes the windows more efficient and extends their service life so you don’t have to repair the window as often as regular windows.
    3. Simonton Windows has a unique price for each fiberglass model window.

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