Glass vs Polycarbonate: What is the Best for Your Greenhouse?


Finding the right type of greenhouse for your specific needs doesn’t have to be a long and difficult process. Greenhouses are great for growing organic vegetables, plants, and even flowers. The ultimate trick is to know what material to use for your greenhouse covering as it impacts the growth of the produce astronomically.

Although glass used to be more popular to build greenhouses with, polycarbonate is the better option today with evolving technologies. Polycarbonate is cheaper and thicker than glass, which means there is less direct sunlight penetrating into the greenhouse. Thicker polycarbonate also helps retain heat inside the greenhouse better.

The sunlight that enters the greenhouse causes the air inside to convert into heat energy. Preventing the heat from escaping the greenhouse is very effective and beneficial for growth.

Okay great, so you have decided to build your greenhouse with polycarbonate and that is that. But, before you go and spend your money, let us first take a look at some in-depth details of the pros and cons and some valuable tips about both greenhouse polycarbonate and glass.

The Pros and Cons of Using Polycarbonate for Greenhouses

Polycarbonate Pros:

Heat Retention

Heat Retention is in most cases one of the main reasons why people prefer to use polycarbonate. The popular choice is the twin-wall polycarbonate, which has a double-glazing effect. This means that the heat inside the greenhouse is retained and is prevented from escaping the greenhouse rapidly.

UV Protection

Polycarbonate offers great light diffusion and UV protection. This means that all the light that is coming into the greenhouse will be spread evenly throughout the entire greenhouse. This will allow you to leave all the plants in one spot without having to move them around to get sunlight, and you won’t need any artificial lighting.

Polycarbonate has a natural UV filter built inside the material itself. This is a great benefit to the plants because the harmful radiation from the sun will not get through the material, and cannot cause any damage and harm to the plants inside of the greenhouse.

Durable

It is a lot more durable and shatter-resistant than glass. It can withstand harsher temperatures and weather conditions than glass, which makes it so much more long-lasting. It can stand its ground from snow, rain, hail, and even a burning sun. It is said that polycarbonate is about 200 times stronger than glass, and therefore there is no need for extra precaution or any extra costs to make your greenhouse safer.

Cheaper

In the case of replacing or rebuilding your greenhouse, using polycarbonate will be much cheaper to use. Polycarbonate is a quite light material, and one can easily revamp or rebuild the greenhouse by oneself. The initial erection cost itself is also a lot cheaper than that of glass. Glass is more expensive and heavier to handle. It ultimately requires a lot more delicacy when handling and maneuvering it, as glass is more prone to breakages.

Longer Growing

A polycarbonate greenhouse allows for a longer growing season for fruits, plants, and vegetables. This is especially helpful when you are in the commercial plant business and want to become a commercial seller. It is extremely advantageous in regards to the return on investment if you are selling your produce. The longer the season, the longer the selling.

The design is flexible. Unlike glass that is a set shape, polycarbonate is a flexible material and cannot be easily broken. The shape and size of a polycarbonate greenhouse can be hand-picked and made to your specific measurements.

Here’s a video from someone whos had both polycarbonate and glass to give their thoughts:

Polycarbonate Cons:

The twin-wall polycarbonate panels are great, but they do have a disadvantage as well. Dust is prone to accumulate between the twin-wall panels, especially if you do not cover the ends with tape or end-covers.

Cleaning

Skipping on cleaning will make it more difficult to get rid of the dirt, and once the dirt builds up, it will have a drastically negative impact on the light transmission into the greenhouse. The dirt will block the sunlight from fully entering and that will disadvantage your overall produce’s growth.

Algae can develop very often if you skip cleaning the polycarbonate greenhouse. It can, unfortunately, stain the inside and outside and if not maintained it can be a permanent stain. The algae can also grow between the panels and will then be almost impossible to clean. Typically, this will also put a strain on the light transmission.

Moisture

Condensation is another big disadvantage when using polycarbonate to build a greenhouse. Moisture, resulting from the temperature difference, becomes trapped between the twin-wall panels and can lead to sunlight not getting through the plastic o benefit the produce’s growth, and this can also lead to algae growth. The condensation can also affect the interior temperature inside the greenhouse which will negatively impact produce growth.

Polycarbonate is a non-natural resource as it is chemically produced and not all that great for nature itself. It also is not as aesthetically pleasing as the glass greenhouses.

Polycarbonate glazing scratches very frequently, especially if one would clean it with a dry cloth. Once the glazing is scratched, there is no way to get rid of the scratches unless you replace the old polycarbonate sheets with new ones.

Here’s a video with some tips for anyone looking to get a polycarbonate greenhouse:

The Pros and Cons of Using Glass for Greenhouses

Glass Pros:

Light

Glass transmits almost 100% light into the greenhouse and will stay that way, if clean, for a lifetime. The light clarity is impeccable, as there is no barrier in the glass that dims the light to the inside of the greenhouse. Whereas polycarbonate greenhouses have a roundabout of 80% light transmission, and eventually fades over time as the material becomes opaque.

Looks Nice

Greenhouses that are made out of glass are aesthetically pleasing, and for many people, it is where the indoors and outdoors become one – with great visibility from the inside and outside.  The glass greenhouse started in the 1700s, and today it still gives that traditional greenhouse look that emphasizes its beauty and luxury. When it is cleaned regularly, it gives a look of cleanliness and sophistication.

It is generally stronger than the polycarbonate greenhouse as the glass weighs a lot heavier. Due to its strong nature, the structure will have quite a long longevity which makes for a great investment and will add to the value of the property.

Options

When choosing a glass greenhouse, you normally have various options as to what layer of glass one would prefer. The options normally are the single-layer, double- and triple-paned glass. They help to improve ventilation and insulation inside the greenhouse. In essence, this means that it uses less energy but is still able to provide better protection for your produce.

Glass greenhouses are durable during fires, rain, and snow; and it is also UV resistant and air pollution degradation. Using glass for your greenhouse covering can function for at least 50 years if it is looked after.

Glass Cons:

Fragile

Although the glass greenhouse can withstand most weather conditions, it still cannot withstand severe weather conditions such as hail, etc. Even if a sharp or hard object hits the glass it can shatter. It is not as durable as the polycarbonate material and the glass is much more fragile and prone to damages.

Heavy

Greenhouse glass is heavy and makes it difficult to have a DIY approach, which in turn will cost you quite some money to get it installed by a contractor. It makes it very time-consuming to prep the set-out space for erection and the ground must be level and not too hard, otherwise, the glass will crack. Erecting a glass greenhouse takes a lot of planning and detail to go through.

Expensive

Glass greenhouses are much more expensive to maintain and to build than it would typically cost for a polycarbonate greenhouse. Especially the double and triple-paned glass, which is a much better quality glass for your greenhouse, but unfortunately you will have to spend some dollars on it.

Due to the level of clarity the glass provides, the plants may be subject to burn as a result. There is not much light diffusion that glass greenhouses offer, so the heat sometimes will not be spread evenly around the greenhouse.

This can lead to some areas being colder and having less light than other areas and this can provoke an overall disadvantage to the growth of the produce.

Here’s another video summing up the differences between polycarbonate and glass greenhouses:

Things to Consider When Buying a Polycarbonate Greenhouse:

Polycarbonate Greenhouse Lifespan:

Polycarbonate greenhouse’s lifespan is about 10 to 15 years before it is time to replace your panels. But, with that said, if your greenhouse was looked after. If it is not cleaned and maintained regularly, its lifespan will lessen.

The best option for the best, long-lasting panels, is to seek out virgin materials that are not recycled. Before buying the polycarbonate panels you should also make sure that the sheets are UV treated on both sides of the panels equally. If it is not UV treated the lifespan will also shorten.

How to Clean Your Polycarbonate Greenhouse?

  • Use a bucket full of warm water – rather too much water so you can completely rinse your cloth out frequently.
  • Use little detergent (only a few drops of washing-up liquid will do the trick).
  • For the prevention of scratches, use microfiber cloths. The dirt will be trapped in the microfiber cloth’s fibers and thus prevent the dirt from scratching the polycarbonate panels.
  • Be sure to wash your polycarbonate greenhouse regularly. However, it also all depends on where your greenhouse is situated and the temperatures in the area on how regular you should clean it. It is better to rather clean your polycarbonate panels sooner than later to prevent algae and permanent damage.
  • Do not wash your polycarbonate greenhouse with a high-pressure washer as the pressure may damage the surface.

How Thick Should the Polycarbonate Be?

Generally, the 8mm panels are used, and the 4mm panels are used as a season extender, but it all depends on where your greenhouse is situated and what weather conditions you are facing.

A good measuring platform is to take the R-value and U-value into consideration. The R-value is the insulation efficiency of the panels and the U-value will indicate the amount of heat loss: the lower the value of the U-value, the lesser the heat loss.

Things to Consider When Buying a Glass Greenhouse:

Glass Greenhouse Lifespan:

The lifespan of a glass greenhouse is especially long due to its heavy weight. It is generally a strong material for greenhouses unless it breaks due to severe weather. Normally the average lifespan of glass greenhouses is between 40 to 50 years. Not too much maintenance is needed.

How to Clean Your Glass Greenhouse?

  • Evacuate the entire greenhouse so that it is empty. Only restock the greenhouse once all the cleaning is done, and the house is dry again.
  • Use glass cleaner as a detergent and pour the solution into a bucket full of lukewarm water.  There should be plenty of water in the bucket so that rinsing can be done effectively.
  • Use a sponge to wash the glass panels – the inside and outside will both need cleaning.
  • Wipe down all the other dirty surfaces, and remove all dirt and or leaves in the gutters and on the ground.

What is the Best Glass to Use?

Tempered safety glass is the way to go in this case. Safety glass is one of the strongest glasses there is to prevent damage. It is 4 to 6 times more robust than annealed glass – it is the typical bulletproof glass. When the glass shatters due to damages, it breaks into small pieces, which makes injury or damages very low.

Double-pane tempered glass is the best and safest option, although it is quite pricey. The 4mm glass is much stronger than the 3mm glass and would be the perfect option.

Laminated glass is a bit safer than tempered glass because when damaged it forms a “spider web” and the glass does not shatter – causing no injury whatsoever. But there are many complaints about leaks, making it less popular to use as greenhouse glazing.

Conclusion

The essence of a greenhouse is to favor growth on the inside in the best way possible. When looking at this, having a polycarbonate greenhouse is the way to go, because it is a thicker material that does not let in so much direct sunlight. When this happens, the light is spread more evenly throughout the greenhouse, and much more beneficial for the growth of all your produce.

Polycarbonate greenhouses are also cheaper to start with, and it does not take that much of your time to ‘garden’ your greenhouse. Because the light is spread out evenly and enabling the heat to be spread out evenly as well, making it much more convenient not having to move your produce around to find the most favorable spot in the greenhouse.

Starting your own greenhouse is a great hobby and you can even make some money out of it if you go commercial. It all just comes down to what preferences you prefer and what your style is. The main thing is to have fun with it, and ‘greenhouse’ within your means!

Robert Sampson

I'm Robert Sampson and I live in Colorado where I spend a lot of time in the backyard with my family either grilling, playing games and sports, or working on a project to make our backyard a better place to be.

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