April 26, 2018
Selecting the appropriate material for greenhouse covering requires careful consideration of the insulation, light transmission, cost-efficiency and durability a grower desires. Greenhouse cladding comes in a variety of materials, including glass, acrylic, poly film, polycarbonate and more. When a grower searches for their ideal cladding material, they should bear in mind the types of crops they will grow, the climate they live in and the placement of their greenhouse.
Poly film, double poly film and twin wall polycarbonate are great options that will suit most growers. Let’s take a closer look at the light transmission, R value (heat insulating factor) and the price point of these cladding options.
Greenhouse poly film, a flexible material that comes in a range of thicknesses, is popular with many growers because of its low cost, tensile strength and durability. Many of Growers Supply’s poly film options are UV-protected, ensuring they will endure years of sun exposure without yellowing or weakening. The film’s high translucency ensures good light diffusion and reduces shadows. It’s also easy to install poly film, even for those with only modest building skills.
When compared to glass, poly film is better at absorbing heat and it can even save growers up to 40% on heating costs. Structures cladded with poly film can be used throughout the growing season, making it a versatile choice for growers.
Poly film is translucent and can offer light transmission around 90 percent, the highest value of the three materials on this list. What it gains in light transmission however, it sacrifices a little in insulation. Its R value of .83 means that it may not be warm enough for year-round usage, depending on the region. Poly film is a good choice for cold frames, high tunnels and hoop houses, and appeals to many growers because it is easy on the pocket as well.
GrowSpan provides poly film in a range of mils (a mil is 1 thousandth of an inch.)
- 6 Mil 4 year film: The most popular greenhouse cladding offered by Growers Supply. When fastened securely, this film can actually last up to 8 years.
- 6 Mil 4 year Infrared/Anti-Condensate film: This film provides infrared additives to help retain heat and block some types of UV light from entering the greenhouse. This can be helpful to plants sensitive to high levels of radiation. The anti-condensate properties encourage water to sheet down the side of the film, minimizing condensation and dripping. It also functions perfectly as an inside layer of double-layer greenhouse film.
- 3 Mil 1 year film: This is a good solution for temporary projects.
- 3 Mil 1 year white film: This type of film is mainly used for overwintering or protecting plants from the cold. It’s a great short term solution for growers who need one season of winter coverage, as opposed to year-long growing.
- 6 Mil Sun Master clear greenhouse film: This poly film offers over 90% light transmittance and is considered the standard in greenhouse cladding.
Double Poly Film
The light transmission of double poly film is close to 90 percent, providing ample but slightly softened sunlight. This soft, natural light is not just soft on the eyes, it also helps prevent the burning of plants.
With double poly film, growers are able to inflate the space between the two layers with just a small fan. This creates a beneficial air pocket that improves the R value. Because of this, growers can expect an R value of about 1.5. Since double layer poly cladding is two layers, it is slightly more expensive. However, it is still an economical option, especially when growers factor in the improved insulation properties.
8 mm Twin Wall Polycarbonate
Polycarbonate is another popular choice for a greenhouse covering across a wide variety of climates. In particular, 8 mm twin wall polycarbonate provides practically shatter-proof protection from impact and weighs 1/12 as much as glass. Due to its strength and lightness in weight, it is widely used in construction, rain shields and soundproofing applications. It’s become a very common substitute for glass, and for most growers it’s a better option.
GrowSpan uses 8 mm twin wall polycarbonate panels on its own Series 2000 Commercial Greenhouse, which has earned the nickname “bomb proof.” The air pockets between polycarbonate sheets stand up well to extreme weather conditions, since they retain heat in cold temperatures and stay cool during warm months. The hollow, double-layer construction of 8mm twin wall polycarbonate provides the highest insulation factor with a 1.72 R value.
The more layers a cladding sheet has, the less light is transmitted. Thusly, growers must determine which is more important for their greenhouse –light transmission or insulation. 8 mm twin wall polycarbonate blocks virtually all UV penetration and has a light transmission of about 80%. It is the priciest of the three cladding options, although still the best choice for commercial or professional growers.
8 mm twin wall polycarbonate is designed to survive for many years of use without showing signs of yellowing, fading or discoloration. Its thermal efficiency is what makes it possible to establish a year-round growing environment. This stabilizes indoor temperatures, cuts down on utility costs and reduces an operation’s carbon footprint.
GrowSpan and Growers Supply have greenhouse cladding options for every grower, from the backyard hobbyist to huge commercial operations. Whether a grower is replacing an existing greenhouse covering or building a new greenhouse from scratch, considering these cladding factors can make the difference between struggle and success.
For more information on how to choose the right greenhouse covering, Request a Quote or contact a Greenhouse Specialist today.