But one rule to know and remember when it comes to glazing: It must always protect your greenhouse from all seasonal antagonists. This includes bitterly cold and oppressively hot temperatures, heavy snow loads, and golf-ball sized hail. As a rule, your climate should determine your glazing.
For those unfamiliar with the term, the glazing is the material that will cover your greenhouse. That means it is also the material that will protect your greenhouse from season to season as temperatures fluctuate, precipitation changes, and light levels shift. For example, growers in California often require different glazing than one near our headquarters here in New England.
Choosing Your Glazing
The glazing material that you choose will certainly depend on your location, but also your crops and what you are willing to invest in your operation. There are distinct differences between the several options available. It is important to keep in mind these variables will vary from operation to operation dependent on the aforementioned variables.
Let’s take a closer look at some of those variables.
Light – Plants grow optimally at 70 – 75% of available light. Heat stress occurs for plants just as it does for our bodies from over-exposure to the sun. To avoid this problem, glazing diffuses direct light. The amount of diffusion will vary from one material to the next. As light passes through the glazing and into the greenhouse it will fan out and bend around corners. This leaves fewer shadows. This is a good thing. Shadows do growers no good in the greenhouse. Plants in these conditions have been shown to 30% faster when all leaves are exposed to light, as opposed to just the upper canopy of the plant.
Longevity – The longevity of the various options is purposefully varied. If you’re growing in a temperate region with little seasonal variations you may be able to pull off a few seasons with just one installation of poly-film – double layered is probably a better option if you’re going for longevity. If you’re in an area with frequent storms, strong winds, and heavy snow loads then you will require a durable material built to withstand these extremes. Warranties are vital to repairing broken glazing so keep that in mind when choosing a material for your operation.
Insulation – Thermal efficiency is the key to saving on energy costs. All of the materials have various sub-options to consider that will maximize energy efficiency. The goal is to retain heat in the cooler months and to help regulate over-heating during the warmer periods of the season. This breakdown from Greenhouse Gab is a useful starting place.
The three main glazing materials are glass, polycarbonate, and poly-film. While historically glass was the only option, technological advances have provided a variety of alternative, more durable options for greenhouse owners. For instance, glass doesn’t take well to large hail or windblown objects and single-layered poly doesn’t like strong winds or heavy snow loads. Getting the glazing right the first time will save you on retrofitting your greenhouse down the road.
Glass: This option is the oldest of the greenhouse glazing options. For its translucence, glass has been the go-to option in the past – as it has for aesthetics. It is hard to deny that glass is the most attractive of the glazing options.
Yet, glass does not diffuse light as well as alternative materials, and this does not generate optimal light levels or growing conditions for plants. Glass also gives little leeway in terms of installation. Installers must be precise with everything they do and be cautious not to bend the brittle material. Maintenance costs pile up quick with broken panes and hourly workers.
Advantages: Longevity, aesthetics, light clarity
Disadvantages: Brittle, costly to replace, poor thermal efficiency, plants can still burn
Polycarbonate: This option is more than 100 times more durable than glass alternatives. You can purchase polycarbonate in both double, and even triple, layer options. Polycarbonate is what bulletproof glass is made of so you can rest assured your space is safe no matter the conditions.
Plus, the space between the layers can actually increase insulation and help convection, reducing energy costs for your operation. Again, a warranty can save your costly maintenance in the future and here at Rimol we offer a 10-year warranty to put your mind at ease.
The material is easy to cut and will not break as glass will if bent during installation. It will also diffuse light evenly for your crops and prevent burn from over-exposure.
Advantages: Excellent thermal efficiency, durable, longevity, diffuses light for optimal light levels
Disadvantages: Prone to scratching, may become ‘yellow” or discolored if not UV-treated polycarbonate
Poly Film: This is a preferred option for growers in warmer climates. If insects are destroying your crops then a single layer of poly with ample ventilation can thwart those costly infestations. The same goes for diffusing direct light if your plants are stressing out. It is possible to insulate poly-film by adding to layers with an air-filled space between. It won’t do much in the face of plummeting winter temperatures but will protect from a nip of frost on those first cool autumn nights.
Advantages: Low cost, diffuses light and aids photosynthesis
Disadvantages: Short lifespan, easily torn or damaged, poor thermal efficiency (unless double layered)
Each glazing option has its benefits and downfalls. If you would like help identifying the best material for your greenhouse, the Rimol team is always just an email away. Get in touch, anytime.