Types of Glass Used In Greenhouses

Traditionally, glass has been the only type of greenhouse glazing that was available. However, with the emergence of plastic variations, glass glazing is no longer the sole option. In this post, I will talk about the various types of glass glazing that are available.

So, what is the best glass glazing for a greenhouse?

Double-pane tempered glass is the best choice for a greenhouse as it is robust and can withstand the elements. It also breaks down into small pieces in case of damage.

  • Horticultural glass
  • Heat-strengthened glass
  • Laminated glass
  • Toughened glass
  • Tempered glass
  • Insulated glass

Horticultural Glass Greenhouse

When it comes to choosing the glass for your greenhouse, there are two main options: toughened safety glass and horticultural glass. The former is the most durable and is usually used for outdoor use.

Toughened safety glass is more durable and is more resistant to breaking. However, it’s still a safer alternative to using polycarbonate.

This type of glass is commonly used for greenhouse applications. It has a 3mm thickness and is known as annealed glass.

An annealed glass is generally considered the most economical type of glass. However, it is also very fragile and can get broken by kids.

Due to the nature of the glass, it can break into long sharp shards that can injure people. In terms of safety, I would consider using toughened glass.

Toughened Glass Greenhouse

Aside from its appearance, a greenhouse should also be considered for its durability and safety. There are two processes that can be used to strengthen and temper its glass.

Although the two techniques are based on the same heat-treating process, they differ in how they affect the strength of the glass.

Heat-strengthened Glass Greenhouse

The process of making heat-strengthened glass involves slowing down the cooling process. This lowers the compression strength of the glass.

When broken, the glass has a pattern similar to annealed glass, which stays in the frame for longer. This prevents it from falling and injuring people.

Tempered Glass Greenhouse

The cooling stage of glass is faster when compared to the untreated one. In addition, the toughened glass is up to 5 times more robust.

When a glass container is broken, it can crack into small pieces and fall from the frame, which is not ideal for a greenhouse.

According to the building codes, tempered glass is a type of safety glass that’s designed to meet the requirements of the building. However, in terms of durability, I would prefer to use laminated or insulated glass.

Laminated Glass Greenhouse

A laminated glass is a type of safety glass that consists of two pieces of glass. It doesn’t break into long pieces when broken.

The broken glass is attached to an interlayer made of a type of plastic that has a spider web cracking pattern. This prevents it from causing damage to the plants.

Since I’ve never tried a laminated glass, I’m not gonna try it out. But, in the comments section, let me know what you think about the product.

Insulated Glass Greenhouse

Insulating glass is made up of several sheets of glass that are held together using a combination of air and dry air space.

Typically, insulated glass is double glazed, consisting of two panes of glass; however, due to rising energy prices, the triple pane is becoming increasingly popular.

So, whether you want to make your own insulated glass or buy one, keep the following considerations in mind:

  • Simply take two clean sheets of glass of the same size and sandwich them together with a spacer.
  • A spacer is typically a metal or polymer strip with a drying agent, such as desiccant, that absorbs moisture that forms between the glass sheets.
  • The appropriate gap between the glass sheets is between 10 and 20 mm; the smaller the gap, the better the thermal performance.
  • Because the glass sheets are completely sealed, the empty space between them acts as an insulator, preventing cold air from entering the greenhouse.
  • A low conductivity inert gas such as argon can be used to fill this gap for greater insulation (higher R-value).

Because of the safety considerations, tempered glass is a smart choice for a greenhouse. If you decide to buy one or build one yourself, I would recommend going with tempered glass.

How Thick Should Greenhouse Glass Be?

A 4mm thick greenhouse glass is enough for most applications, but triple panes are expensive and unnecessary. After checking the glass’s seals, double glazing can last up to 10 years.

This product is not suitable for use inside a greenhouse. Also, it is not very durable and can cause the seal to break quickly.

Using Low-E Glass in a Greenhouse

The use of low-E glass in growing greenhouses helps protect tender plants from UV light and promote healthy plant growth. Unfortunately, some manufacturers try to downplay the importance of this technology.

The use of low-e coating on greenhouse panes can reduce the amount of heat loss compared to standard glass. However, it still retains the same visible light transmission.

To combat rising energy expenditures, glazing technology has advanced tremendously. To improve energy efficiency, a special coating for glass is used.

A low-emission (low-e) coating is one of them, and it has become popular among gardeners.

What is a low-e glass, exactly?

It’s a single pane of clear glass that’s been coated with a tiny coating of metal oxide that’s been deposited microscopically.

The low-e coating eliminates the harmful effects of ultraviolet light and infrared light on plants. It allows them to absorb and use photosynthetically active radiation.

The low-emission coating on a building contributes to the heat’s return by reflecting it back to its source. In winter, this effect occurs when the greenhouse’s heat tries to enter the building.

Best Glass Glazing for a Greenhouse Roof

Insulated glass with laminated glass panes on the outside and tempered glass on the inside would be the best glass glazing for the roof. The laminated glass will withstand the weight of the snow and will not shatter into tiny pieces.

Double pane tempered glass is the ideal glass glazing for a greenhouse. It is durable, and if it is damaged, it splits into little square pieces, reducing the risk of injury and ensuring that small fragments do not harm your plants. In greenhouses, what kind of glass is used? Horticultural is a 3mm thick standard glass. Annealed glass is another name for it.

Glass vs Polycarbonate Glazing

Clear glass has traditionally been used to construct greenhouses. A clearer view of the inside of a greenhouse improves its visual appeal and gives it the classic aspect that it is known for. Polycarbonate panels, on the other hand, are slightly opaque, so you won’t get the conventional greenhouse look.

Because glass is clearer than polycarbonate, it transmits more light, allowing your plants to get more natural light.

Which One Is Stronger?

Although polycarbonate panels are very strong, standard greenhouse glass is prone to breaking. Fortunately, there are various types of toughened and laminated greenhouse glass that are incredibly resilient.

Polycarbonate and glass panels are both designed to endure the elements and have a long lifespan. They can also be flame-resistant, making them ideal for outdoor entertaining.

Polycarbonate greenhouse glazing is a better choice than glass for cold climates due to its light-diffusing properties and heat-retaining capabilities.

Difference Between Greenhouse and Glasshouse

A greenhouse is a building with a glass or plastic roof and, in most cases, glass or plastic walls. Its roof and sides must be able to let light in. A greenhouse that is made of glass is referred to as a glasshouse. Because glass was previously the sole material suited for this purpose, the terms “glasshouse” and “greenhouse” were almost interchangeable.

Does Greenhouse Glass Become Brittle?

Keep in mind that as glass ages, it becomes fragile and more prone to breaking. When working with glass, always wear protective gloves because it’s all too simple to sever your fingers. The glazing clips that keep the glass in place are prone to disappearing. It’s a good idea to keep several extras on hand and replace them as needed.


If you have a greenhouse and need replacement glass, or are considering building one, you may be wondering whether glass or polycarbonate glazing is the best option. As a result, we’ve decided to compare the two in order to assist you in making your decision.

Wrap the interior of a glass greenhouse in plastic or bubble wrap during the colder months… This adds the extra layer of heat efficiency you’ll need to save money on your heating bills.

The best material for glazing is glass, as it lets in as much light as possible and, unlike plastic, does not shrink or degrade in sunlight.

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