Greenhouse glazing, that’s the clear stuff that covers your greenhouse, comes in many different materials these days. When you are choosing your greenhouse kit or planning your greenhouse construction, you need to decide which glazing material will suit your needs.
The four most common glazing materials are:
- Glass
- Rigid Plastic
- Polyethylene Film
- Fiber Reinforced Panels (FRP)
Glass of course, is the traditional glazing material for greenhouses. It is not used as much any more. Mostly people designing and building their own greenhouse use glass, because they can find old windows for cheap or free. The advantages of glass are that it lets a lot of light through and it lasts a very long time, if it is not broken. Glass is also more environmentally friendly than plastic. The disadvantages are weight, fragility, and cost, unless you are a scrounger and don’t mind the look of a greenhouse made of old windows.
Rigid plastic is used almost exclusively in modern greenhouse kits. Plastic is light weight and relatively inexpensive. Acrylic does not degrade with UV light, but is does scratch easily and it expands and contracts, making installation more difficult. Polycarbonate is UV resistant but does lose effective transparency after ten to fifteen years. Double or triple walled polycarbonate retains heat very well and is very easy to install. It is the most common greenhouse glazing these days.
Polyethylene film is the cheapest and shortest lived glazing material. It typically lasts one or two years. In the long run it is not so cheap, especially if you buy greenhouse grade. Greenhouse grade works much better, but does not last much longer. Even the best film, in the best circumstances, only lasts three or four years.
FRP is another inexpensive glazing option. However the more expensive ones with UV resistance can last up to twenty years. One big advantage is that it diffuses light, so that it spreads evenly. Even though it diffuses light, it still lets a high percentage of the light through. Many people do not like the look of FRP, and it does not come in any greenhouse kit that I am aware of. However, if you are building your own, FRP is definitely worth considering.
My personal first choice for greenhouse glazing is glass, or a combination of glass walls and FRP roof. If I were buying a greenhouse kit I would get polycarbonate. If I lived in a cold climate, I would get triple walled polycarbonate, whether I was building my own greenhouse from plans or buying a greenhouse kit.
