Greenhouse Glazing Options & How To Choose

greenhouse glazing close-up

The glass in your greenhouse plays a big role in determining its safety. Glass is the main component of a greenhouse, and this means you need to think carefully about the glazing option that you choose when you’re buying a greenhouse.

Not all glass is the same. Some types of glass will give you more safety and efficiency than others. Let’s take a look at some of today’s most popular types of glazing for greenhouses right now.

Horticultural glass


  • Cheaper price


  • Glass shatters into dangerous pieces
  • Overlapping pieces
  • Hard to clean

3mm horticultural glass is the option most commonly offered by greenhouse retailers.

This is commonly used due to its low cost but it is weaker than several of the other options available to you. This kind of glass can shatter easily, which is why so many people are now seeking out tougher options.

No matter what make or model you’re opting for, horticultural glass is generally the same. Each individual pane will measure 2ft by 2ft and will overlap midway on each part of the greenhouse. The panes are held together with S or W clips. Multiple clips are normally used to secure each of the panes into place. The more clips you have, the more protection against wind damage you will have.

A big drawback of 3mm horticultural glass is that it forms large, sharp shards when it breaks. This means it could be a very dangerous option if you have kids or pets around.

It can also be hard to clean greenhouses that have 3mm horticultural glass. This is because algae and dirt tend to gather in the joins where the panes meet so you can’t normally clean them as thoroughly as you might want to. It is somewhat common for bar capping to be used with these systems. This is due to the way that it gives you more protection from wind damage. It can also make your greenhouse look tidier thanks to the way it disguises the metal clips.

Polycarbonate glazing


  • Safest option
  • Lightweight


  • Weaker, not designed for windy areas
  • Reduced light
  • Attracts mildew and bugs

Twin-wall polycarbonate glazing might be the option for you if you need an alternative to horticultural glass. It will give you extra protection, especially during the winter months. However, it does come with a few drawbacks. As polycarbonate is very lightweight, it can make your whole greenhouse vulnerable to wind damage. It’s not uncommon for panels to pop out of the framework when the elements attack it. This can be not only irritating but dangerous.

Another drawback of polycarbonate is that it may reduce the amount of light in your greenhouse. This is because it has a corrugated texture. As the plastic gets older and loses colour, you can expect light levels to fall further over time. Polycarbonate can also be hard to clean. The panels can pop out when you apply pressure to them. The twin-layer plastic can also attract mildew and bugs. When these appear between the panes, they can be virtually impossible to remove. You can expect your growing environment to be negatively impacted by this, whilst light levels drop further.

Browse Polycarbonate Greenhouses

We also have an article on the best polycarbonate greenhouses.

Toughened safety glass


  • Shatters into small pieces when broken (safer)
  • Visually appealing
  • Strong
  • No overlaps (less dirt/easier to clean)


  • Most expensive option

Toughened safety glass might be an option for you if you need greenhouse glazing that’s both safe and sturdy. It can also offer a great deal of longevity. If you’re based in an exposed location like a coastal region or an island, this might be your best option. This toughened glazing is designed with safety in mind. If a panel does break, it will break into thousands of tiny pieces so there are no large sharp edges to worry about. The glass has rounded edges so you don’t have to worry about cutting yourself when you install your greenhouse.

The glass panes protect the integrity of your greenhouse and work even better when you combine them with a tough frame. As the large panes don’t have overlaps, it’s easy to clean your greenhouse. What’s more is that you’ll encounter fewer drafts in comparison to horticultural glass panes that do have overlaps and are well-known for attracting dirt and algae.

Shop Toughened Glass Greenhouses

Cleaning and Maintaining Your Glazing

It’s very important to keep your greenhouse as clean as you can. If your greenhouse becomes dirty, the environment won’t receive as much light as it needs. This means your plants will suffer. The dirtier your greenhouse is, the easier it will be for pests and diseases to find their way inside.

Make sure you’re cleaning your greenhouse thoroughly at least annually. It’s easier to clean and maintain a greenhouse during the winter when your greenhouse is emptier. Try to do it before the start of the growing season as this will allow you to take full advantage of the sunnier months.

Which Type is Easiest to Clean?

Toughened glass is normally the easiest type of greenhouse to clean. It is safer and more practical to clean this kind of glass. You don’t have to worry about challenging grooves that dirt can easily become trapped in, and the glass is tough enough to withstand a thorough scrub.

Polycarbonate greenhouses can be tough to clean. This is largely because they have corrugated plastic and twin layers which have various nooks and crannies which grime can easily get into. The panels often shift and flex, which means it can be hard to apply sufficient pressure into the grooves when you want to scrub your greenhouse.

Although horticultural glass is fairly easy to clean, you’ll need to be very careful when you’re leaning on the glass. These panes are smaller than toughened glass, and the panes are often overlapped. This can lead to problems with grime that’s hard to clean.

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What If My Greenhouse Glazing Breaks?

It’s likely that some of your greenhouse panes will break at some point. Breakages may be particularly frequent if you have horticultural 3mm glass. A local glass specialist may be able to replace some panes, but you might have trouble arranging a replacement if you have polycarbonate panels. You may need to get in touch with the specific manufacturer of the glass if you can’t find it anywhere else.


We hope you enjoyed our article on greenhouse glazing.

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matt garner Author: Matt Garner
I'm an amateur gardener based in Birmingham in England, utilising my 30 years experience to help others learn all about gardening for South West Greenhouses. My specialist expertise are with assembling and dismantling greenhouses of all shapes and sizes. I've spent countless years growing fruit and vegetables at Walsall Road Allotments, and I was also a proud member of the Balsall & District Horticultural Society for many years. Linkedin | Twitter