Does Greenhouse Plastic Block UV Rays?


There are many various types of plastic used for both constructing and covering modern greenhouses. One of the biggest factors considered when choosing a plastic for greenhouse plastic is UV resistance. This leads to the question, does greenhouse plastic block UV rays?

Most greenhouse plastics are designed to block UV rays to some degree to protect the plastic and the plants within the greenhouse. Some modern plastics are designed to let UV rays in to better mimic natural growing conditions. Acrylic, polycarbonate, and polyethylene are all used for greenhouses and block different amounts of UV rays.

Not all greenhouse plastics block UV rays, as blocking out UV rays is not always the best way to cultivate successful crops. That being said, most greenhouse plastics are UV resistant. Let us take a deeper look at whether or not greenhouse plastics block UV rays, which plastics block the most UV, and how this affects plants in a greenhouse.

Does Greenhouse Plastic Block UV Rays?

Modern greenhouses are usually built from, or covered with, some form of plastic. There are many various forms of plastic used for greenhouses, and they each have their own benefits.

These plastics were developed to replace glass that was traditionally used for greenhouse paneling. Glass is somewhat effective for blocking out UV rays, especially harmful UV rays, while being entirely resistant to the harmful rays themselves.

This means that glass is not damaged by UV rays, and it is relatively effective at blocking out UV rays while still allowing sunlight into the greenhouse.

Do modern plastics share these same characteristics that made glass so effective for greenhouses of the past? Do greenhouse plastics block UV rays?

  • The plastics that are used for constructing and covering modern greenhouses are usually UV resistant.
  • These plastics are usually designed this way so that the UV rays cause minimal damage to the plastic itself.
  • UV rays degrade plastic very quickly, and so they must be designed to block as much of this harmful radiation as possible.
  • The plastics used for greenhouses usually have a coating on them that protects them from UV rays.

This UV-resistant coating on the plastic used for greenhouses, whether plastic panels or plastic sheeting, means that greenhouse plastic does block UV rays – to some extent.

Transparent plastics allow more sunlight and more UV rays to enter the greenhouse than opaque plastics do, and the modern polyethylene bubble-wrap sheeting is more effective for blocking out UV rays than standard polycarbonate coverings.

Here’s an in depth video about the different types of greenhouse materials, with more info below on specifically blocking UV rays:

Do All Greenhouse Plastics Block UV Rays?

Almost all modern greenhouses are made from plastic or covered with plastic. This is because plastic is a more cost-effective, sturdy, weather-proof, reliable, and workable material than the greenhouse glass that came before it.

While most greenhouses make heavy use of plastic in some way, not all greenhouses use the same type of plastic. There are multiple types of plastic that are used for the construction and covering of greenhouses, and each of them have their own characteristics.

The fact that such a wide variety of plastics are used for greenhouses means that not all greenhouse plastics block out UV rays. 

  • The greenhouse plastics that do block out UV rays generally last longer in the sun and are far more resilient than other plastics.
  • These plastics tend to last well in all types of weather and can be left outdoors for many years.

Not all plastics have this feature, however, which makes them far more susceptible to weather and sun damage. Greenhouse plastics that are not UV resistant do not last as long as the plastics that are, but they do have other advantages.

Greenhouse plastics that allow UV light to enter the greenhouse provide a more natural growing environment for plants, as UV rays are present when growing outdoors.

These plastics do degrade far more quickly, but many growers intentionally use them for the natural growing environment that they provide within the greenhouse while still being strong and sturdy enough to maintain growing conditions and protect the greenhouse plants.

Which Greenhouse Plastics Block The Most UV Rays

If you are looking for greenhouse plastic that is well suited for blocking, filtering, or absorbing UV rays, there are various types of plastic on the market that can be used.

Using a UV-resistant plastic has many benefits, but there are some disadvantages to using this type of plastic for greenhouses.

Nevertheless, the greenhouse plastics that block the most UV rays are acrylic, polycarbonate, and polyethylene.

These three plastics are used in various forms, and they each have their own properties that make them good for use in greenhouses.

Acrylic is the first UV resistant plastic on the list for a good reason. Acrylic is used as paneling for greenhouses and is strong enough to construct the entire greenhouse from.

  • This type of plastic can be made to be clear or opaque, but even the transparent form of acrylic is covered in a UV resistant film that blocks out the majority of UV rays.
  • Acrylic is tough and provides very good UV protection for greenhouses while being a good thermoregulator to keep warmth in the greenhouse and still allowing sunlight into the greenhouse.

Polycarbonate is a very versatile greenhouse plastic and is either used as thick greenhouse panels or as a greenhouse film.

  • This plastic is either combined with a UV resistant chemical when it’s made, or a UV resistant coating can be applied to it to better block UV rays.
  • Polycarbonate is effective for blocking UV rays but is far less tough than acrylic, especially when used as a plastic sheet.

Polyethelene is a relatively new plastic for greenhouses, as it is used to make specialized bubble-wrap coverings for large greenhouses.

  • This material, used in this way, is very effective at blocking out UV rays while still being light and flexible.
  • This plastic is thin, but it is stronger than standard polycarbonate plastic sheets for greenhouses and blocks out as much, if not more, UV light.

How Does Blocking Out UV Rays Affect Greenhouse Plants?

There is some conflict regarding blocking UV rays in greenhouses. Low UV levels in a greenhouses do help to keep parasites and insects at bay, and UV radiation that is harmful to the plant itself in the long term.

However, plants naturally grow outdoors and are fully exposed to UV rays, and there are studies that show that almost all plants grow to be more healthy and fruitful when grown in UV light.

For this reason, there are many growers who do not use UV resistant plastic for their greenhouses.

Blocking out UV light can hinder the fruitfulness of greenhouse plants, but it does help the plants to last longer overall. UV light is damaging to all plants over time, so blocking it out can be of benefit for greenhouse plants.

Conclusion

Greenhouse plastic comes in many forms, including thick plastic panels and thin plastic sheeting.

The way most modern greenhouse plastic is made makes it resistant to UV light for the protection of the plants in the greenhouse and to help the plastic itself last longer while being exposed to sunlight.

Most greenhouse plastics do block out UV rays.

However, not every type of greenhouse plastic blocks out UV rays, as some growers prefer to let UV light into their greenhouse to promote certain aspects of plant growth that occur naturally outdoors.

Whatever plastic you use for your greenhouse will probably be UV resistant on some level. Whether you use hard acrylic panels or polyethylene bubble wrap for your greenhouse, there are plenty of various plastics to protect your plants from UV rays!

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.

Recent Posts