Greenhouse Glazing

Greenhouse glazing is a term used to describe the material covering the outside of your greenhouse. For anyone in the process of designing his or her dream greenhouse, beyond style and location, the type greenhouse glazing you choose is one of the most important choices you will make when either ordering your greenhouse kit or building one from scratch.

As with everything we’ve outlined here at the DIY greenhouse; there are many things to consider when choosing the correct type of greenhouse glazing to suit your needs. The top three considerations for anyone reviewing possible selection for glazing materials should be:

  • The perfect covering should allow the maximum amount of sunlight to enter your greenhouse while stopping as much heat as possible from exiting the structure.
  • It should be durable enough to endure your local climate while at the same time not requiring a significant amount of time for maintenance and upkeep on your part.
  • As with everything you have to consider your overall budget when selecting your glazing material. Some materials are far cheaper than others, though this does come at the price of efficiency and durability. Only you will be able to determine what the proper balance between cost and function is for you.

There can be a variance of approximately 80 – 90% for visible light transmission from one material to the next. A general rule of thumb we once read in a book was that for every 1% reduction in the light that a plant is able to take in (thus transferred by your glazing material) you could expect a 1% loss in that plant’s growth. If you’re using your greenhouse to help feed your family, this could really be a large concern for you. Choose your material with care!

Greenhouse glazing comes in many different types materials, we’ll go over in greater detail each of these materials in later postings, but a general summary is below.

Greenhouse Glazing Materials

Glass – Glass is the most traditional material used for covering a greenhouse. It’s use stretches back over the centuries as the “go to” material for building greenhouses. Glass offers excellent visible light transmission to aid in the growth of your plants, and many would argue offers the best looking type of greenhouse. Glass is, well glass – it can break easy, is expensive and weighs more than other types of glazing material. This means your greenhouse will need to be sturdier and on a solid foundation in order to support the extra weight – thus adding even more cost.

Polycarbonate – Polycarbonate is a wonderful synthetic replacement for glass. It is lighter, cheaper and more flexible. It will also offer more resistance to impacts from hail or a child’s errant ball toss. Polycarbonate can also be rather expensive, especially if it is multi-layered for heat retention purposes. It is also not as efficient at light transmission as glass.

Acrylic – Acrylic panels used to cover a greenhouse have similar clarity and light transmission characteristics to glass, at a much lower cost. It is also more impact resistant and lightweight than glass. Acrylic materials do have downsides however; they can turn yellow over time when exposed to the sun and are flammable. Because of the non flame retardant characteristics of this glazing material it is not commonly used in industrial greenhouses. You will need to check with your local permitting office to see if acrylic glazing is allowed for residential greenhouses in your area.

Fiberglass – Fiberglass was first introduced to greenhouse builders and dreamers as a replacement for glass itself. It is lightweight, cheaper, offers better light diffusion characteristics and is also well suited for greenhouse heat retention.  Despite all of these great attributes, fiberglass is not commonly used today and has been replaced mainly by polycarbonate. This is because cheaper fiberglass panels (like those found in some kits) can break down rather quickly and require a lot of attention to insure continued efficiency.

Plastic Film – Plastic film greenhouse glazing is very commonly used these days. It is cheap, simple to install and will easily lend itself to many different types of greenhouse framing; from wood to PVC. Plastic can have durability issues if not properly installed and maintained, and some many argue that plastic film greenhouses look “cheap”.

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As you can see there are many different things to consider when selecting the right greenhouse glazing material for your needs. Be sure to give this all-important choice the careful consideration it deserves.

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