What Is A Polycarbonate Window? | Pros & Cons


While glass has traditionally been the obvious choice for windows, it’s not necessarily the best choice, especially when you want to meet specific needs, including strength, weight support, design flexibility, and ease of installation. Glass is often even impractical for constructing and manufacturing items like skylights, clear barriers, greenhouses, and aquariums. 

Polycarbonate windows are made of polycarbonate plastic and look like regular glass. Polycarbonate’s structure makes them hard to chip, break, or crack. This increases the protection of building occupants against burglars, gunshots, and severe outdoor environment events. They are also versatile enough to meet a wide range of design challenges while also good insulators, and easy to install, making them a lot more cost-effective than glass windows. 

That said, polycarbonate windows are not indestructible or perfect, and they have flaws that become apparent once they are installed. Luckily, as we shall see, most of these flaws can be fixed with protective coatings or using thicker materials. 

This guide will compare polycarbonate windows with glass windows, outlining the advantages and disadvantages of polycarbonate and showing when using polycarbonate windows may be the best solution for you. 

Is polycarbonate as good as glass?

Polycarbonate roof

Polycarbonate is an excellent alternative to glass. In some cases, it is even a better option than glass. It has superior impact resistance, flame retardance, insulation, flexibility, and durability to glass. Its great transparency and low moisture absorption make it an excellent choice for windows, enclosures, safety guards, signs, and more. 

The main difference between polycarbonate and glass is the hardness of the material. Polycarbonate is a lot softer than glass, which means it tends to scratch easily if left untreated. The scratches and scuffs will quickly cover the surface of the window, reducing visibility. 

Usually, this issue can be mitigated by using a protective coating on the polycarbonate surface. However, the protective layer will need to be replaced when it develops scratches. 

When a polycarbonate window is installed correctly using the proper protective coating, it reduces the maintenance costs compared to glass windows. However, using the wrong coating can weaken the window’s strength and decrease visibility. Because of this, it is important to always match the coating to the type of polycarbonate used to improve the life of the polycarbonate window. 

Additionally, when adding the coating to the polycarbonate, the adhesive used on the backside of the coating will also determine how compatible the two materials are. Petroleum-based adhesives will usually react with the polymers in the plastic, causing them to melt and become hazy. 

You can re-increase the visibility of a polycarbonate window after it has faded using special tools, heating, and polishing the damaged plastic layer. The plastic can also be polished by sanding using tools that create minimal heat to avoid distorting the view. If deeper scratches on the window, it may require more work. For this reason, consider limiting the removal of deep scratches to thick polycarbonate windows. 

With polycarbonate, you can get thicker windows for cheap. The thicker the window, the stronger and more durable it will be. Thicker windows also provide the best shatter protection and can be repaired more easily when they get scratched. 

Thinner polycarbonate sheets can be installed over the glass to offer shatter protection and prevent it from breaking due to flying debris. 

What are the disadvantages of polycarbonate?

Working with polycarbonate

1. Polycarbonate is not resistant to scratches.

This is the main disadvantage of polycarbonate windows. For example, if a branch falls on a polycarbonate window, it can easily get scratched. This problem can be solved by properly treating the polycarbonate window or by polishing the polycarbonate after it has been scratched. 

2. Polycarbonate sheets easily expand.

Polycarbonate expands by 0.065mm per meter per degree celsius. It is essential to keep this in mind during processing and installation to avoid sizing and fitting issues. During installation, you also have to ensure that all mounting holes are wide enough to prevent the screw or bolt from sticking as the panel expands. And if you use any glue or sealant on the polycarbonate window, you also have to ensure that it is flexible glue. 

3. Polycarbonate is more expensive than other plastics.

It is often only recommended when you need the extreme toughness and heat resistance that other materials cannot offer. 

4. Polycarbonate has poor chemical resistance.

Many organic solvents can attack it, and it is also highly sensitive to abrasive cleaners, alkaline cleaning products, and solvents. When cleaning your polycarbonate windows, avoid using any cleaners with acetone, benzene, and similar organic solvents. 

5. Clear polycarbonate is often susceptible to yellowing and cracking over time.

It is recommended that you always use polycarbonates that come with UV protection, among other protective coating features, with your polycarbonate windows. 

What are the advantages of polycarbonate?

Polycarbonate green house

1. Polycarbonate is stronger and lighter than glass.

It is over 200 times stronger than glass while also being about 50% lighter at the same time. This means you get the best of both worlds without compromising on clarity and natural daylight transmission. 

2. Polycarbonate also allows you to save on energy costs.

When a building is well-insulated, it becomes more comfortable for its occupants and leads to substantial cost savings. Polycarbonate has much lower U-values than glass, which means it can offer greater insulation, reducing heat loss. This leads to a significant decrease in energy costs for air-conditioning in hot weather and heating in cold weather. 

3. Polycarbonate is fire-resistant.

It has a fire rating of B1, which means, unlike acrylic materials, it will not burn in an open flame. Furthermore, it is a self-extinguishing material, which means any fire on it will go out within a short time. 

4. Polycarbonate offers better thermal insulation than glass.

You get better insulation against the heat and cold by more than 20% over glass materials. 

5. Polycarbonate is easy to install.

It is easy to implement curved designs with polycarbonate, which can be pretty expensive to achieve with glass. You can also use single-length polycarbonate sheets that can be cold-bended on-site to suit any design. Polycarbonate can also be cut or drilled and treated to provide protection against leakages. All this makes it a very easy material to work with. 

6. Polycarbonate is vandal-proof.

Because of its high strength, polycarbonate is the ideal material for safety glazing. It is commonly used in public bicycle sheds, technical products and machines, shelters, illuminated signs, and marine glazing.

7. Polycarbonate offers superior protection from UV radiation.

When used as a transparent roofing option, for example, in a pergola or pool cover, polycarbonate blocks 99% of ultraviolet solar radiation. Compared to the 50% block rate that glass covers offer, it is clear that polycarbonate is the most effective barrier. 

8. Polycarbonate offers better control over light transmission and diffusion.

Because the amount of light coming into a building affects the health and wellbeing of the building’s users, it is nice to know that polycarbonate can be adjusted to transmit specific amounts of light while still providing UV protection and solar heat control. 

9. Polycarbonate is a sustainable material.

It has a very long service lifespan, and any panels you use are also fully recyclable. It is also UV resistant, which means it can be used outside, making it the perfect choice for greenhouses, terrace canopies, boat windows, and basketball backboards. 

Does polycarbonate fade in the sun?

Polycarbonate roof

Polycarbonate is designed to resist heat, cold, sunlight, rain, and snow, and this property allows it to last for many years without fading. 

However, when you use colored polycarbonate, its color clarity will deteriorate over time, making the polycarbonate turn yellow with prolonged exposure to ultraviolet rays. You can prevent this by using polycarbonates that come with UV protection. 

Wondering how long it takes for polycarbonate to turn yellow? Well, if it is treated, it can last over 10 years without fading or turning yellow. However, if left untreated, it may start to turn yellow sooner than that. Luckily, the yellow is only on the surface, and polishing it should remove it and return the polycarbonate to its original state. 

How expensive is a polycarbonate window?

Polycarbonate green house

The cost of polycarbonate windows will vary depending on the manufacturer you use, the size and thickness, and the kind of protective treatment used. Generally speaking, though, it is about 25% more expensive than regular acrylic, depending on the grade. 

If you look at the bigger picture, though, thermoplastics are less expensive than glass. The material is cost-effective, the installation costs are low, and the operational costs are even lower once in use. This is why in the end, you end up saving money by using a polycarbonate window. 

Polycarbonate vs. Windows

Polycarbonate window

  • Polycarbonate is 200 times stronger than glass and 50% lighter
  • Polycarbonate offers better thermal insulation than glass, at 2.7 w/m2.°K for glass and 1.75 w/m2.°K for polycarbonate.
  • When used for windows, polycarbonate has been shown to save energy costs.
  • Polycarbonate offers the best protection from UV radiation, at 99% compared to 50% for glass.
  • Polycarbonate offers effective control over light transmission and diffusion.
  • It is easier to install polycarbonate windows than glass windows
  • Polycarbonate is highly flexible, allowing it to be used in curved designs with ease and eliminating the need for butt joints and specialized skills and tools, which results in even more savings. 

Final Thoughts

As you can see, polycarbonate windows can be a great alternative to glass. Depending on your situation, they may even be the better choice of the two, providing durability, ease of installation, and much-needed peace of mind when you are looking for additional protection from flying debris.

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Zoltan Szatmari

Zoltan is a test and industrial engineer from Europe who loves learning anything new and working on small projects. When he is not working, he is usually hiking or going to the cinema.

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