Greenhouse Installation and Efficiency
The structure of a greenhouse greatly affects harvest efficiency and energy efficiency. The construction of a greenhouse; It includes beams, end wall, side posts, sidewalls and purlins (horizontal beams to beams).
Related Article: What is a Greenhouse? What are the Greenhouse Types?
Covering materials of the greenhouse have a critical importance in terms of efficiency, just like its structure. Choosing the wrong greenhouse cover can cause great harm to the producers.
Before moving on to the covering materials of greenhouses, let's take a quick look at the building and flooring materials and examine the connections between them.
Construction materials
Construction of the greenhouse; can be made of aluminum, galvanized steel, wood or plastic. Each of these is more compatible with a different greenhouse cover material.
E.g; best for galvanized steel, polyethylene sheets or polyvinyl chloride (PVC) based fabrics. If you're on a budget, galvanized-based steel is a good option that doesn't rot from moisture like plastic wood.
Floor
Typical flooring materials for a greenhouse are concrete, porous concrete, gravel and rubble. The flooring material affects both the heat efficiency and light transmission of your greenhouse.
If you are going to use gravel or rubble as flooring, you should think twice because; These materials do not retain heat and do not protect your plants from harmful pests.
As an alternaive; The porous concrete allows water to drain, retains heat better and protects your plants from pests by forming an impenetrable barrier.
Greenhouse Covers (Greenhouse Nylon) and Features
To cover a greenhouse; you can use glass, fiberglass, double layer polyethylene, PVC and polycarbonate. The cover is the most important part of your greenhouse because it will affect how much light your plants get and how heat is insulated.
Each material allows a different amount of light to pass through and offers varying amounts of diffusion. You should be careful when deciding on the material for your greenhouse, because too much light can overheat the plants, while shading can cause the plants to die from lack of energy.
Let's take a look at the properties of each material and examine its pros and cons.
Glass Greenhouse Cover
When people think of greenhouses, a glass structure usually comes to mind. Glass greenhouses are probably the best looking option, however; they may fail in energy efficiency and be costly.
If you choose to use glass, remember that glass does not scatter light, so you will need to decide on a diffusion method for your plants.
There are two main types of glass greenhouses to choose from: single pane and double pane .
Single Compartment
These greenhouses are not suitable for northern regions where crops are grown in colder climates. Single pane glass greenhouses are fragile, break often and cannot withstand the weight of snow. A single compartment greenhouse is also the least energy efficient greenhouse because a single compartment allows heat to escape.
Single pane greenhouses are great for light transmission, but this can still be an issue in areas where too much sun will burn your plants. These disadvantages, combined with the cost of glass, mean that single pane glass greenhouses are better suited to form than function.
Also, heating costs can be double or even triple the amount of double glazing or PVC-based fabric greenhouse. A single pane glass greenhouse has a thermal insulation value, or R-value, of about 0.9, so you will need to find a way to heat your greenhouse during the colder months.
Double-glazed greenhouses are designed to be more energy efficient without sacrificing traditional style. If you still want a glass-style greenhouse, double glazing can cut your heating cost in half. These greenhouses have an R-value of 1.5 to 2.0, making them better for insulation than single glass.
Double-glazed greenhouses may have a coating applied inside to reflect heat and add more insulation to the greenhouse. Before buying a double-glazed greenhouse, you should also know that they are often the most expensive type of greenhouse.
Polycarbonate Greenhouse Cover
Polycarbonate greenhouses are made of thick plastic, making them cheaper and more versatile than most glass greenhouses. This material is superior to glass in some ways, but; However, it is not without its problematic aspects.
These greenhouses usually come with a single wall or double wall polycarbonate sheet.
Although single -walled polycarbonate is more durable than glass, it will cause you problems in terms of thermal insulation and light transmission.
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Single-walled polycarbonate sheets do not diffuse light or insulate heat well. While the R value of the single-walled polycarbonate material is 0.83, the R-value of the greenhouse glass is 0.93. The light transmittance of the single-walled polycarbonate is also lower than the glass. About 94-96 percent of the light passes through the single-walled polycarbonate; 97-98 percent of the greenhouse glass can pass through the greenhouse glass.
On the other hand; Single-walled polycarbonate is a highly flammable material and extreme care should be taken if it is to be used in hot climates with long periods of sunshine.
double wall
Double -walled polycarbonate is better than single-walled polycarbonate in almost many ways.
Double-layer polycarbonate has an R-value of 1.42, which makes it better than single-glazed or single-layer polycarbonate. Double-walled polycarbonate also diffuses light, but 80-84 percent of the light passes through the panels.
Also, polycarbonate panels are known to cloud over time. This turbidity is called the yellowing effect. If you buy polycarbonate panels, you need to watch for the yellowing effect as it will reduce the light passing through the panels.
Finally; Condensation is an additional issue for double-walled polycarbonate, which can cause plant diseases and poor light retention.
Polyethylene Greenhouse Cover
Polyethylene is inexpensive and lightweight, making it easy to handle. Thanks to its flexibility, it can be easily shaped during the installation of the cover.
Polyethylene film is usually made of one or two layers. Oxygen and carbon dioxide can pass through this material. Because; it is porous and allows plants to breathe even in a tightly closed greenhouse. Polyethylene greenhouse cover is perfect for growers because you can customize the material with different coverings. A UV stabilizer can be used on polyethylene film to reduce sun degradation and yellowing, while an anti-drip coating will prevent excessive condensation.
Another useful coating is polyethylene glass that diffuses light. The diffusion coating allows growers to maximize the sun's efficiency of the site by ensuring all plants receive sunlight. Compared to glass, the polyethylene film reduces heat loss by 30-40 percent. In addition, the R value of the single-layer polyethylene film is 0.87, while the double-layer films range from 1.5 to 1.7.
Finally; unfortunately, polyethylene films are still moderately flammable. More than glass materials in terms of flammability, but; We can say that it has less value than polycarbonate materials.
Fiberglass Greenhouse Cover
Fiberglass Reinforced Plastic (FRP) is another good option for your greenhouse. FRP scatters sunlight, provides good diffusion and light transmission throughout your greenhouse, and can last up to 10 years.
Fiberglass panels have an R-value of 0.89, which is slightly better than glass. However, UV rays can break down the fiberglass over time, making the cover brittle. To maintain the strength of your fiberglass panels, you will need to apply a new UV coating every few years.
PVC Greenhouse Cover
In terms of durability, Polyvinyl Chloride (PVC) fabric is the best choice. Some PVC fabrics can withstand heavy snow loads and offer higher insulation, making them good for growers in cold climates. Translucent PVC fabrics with UV treatments, including types designed with UV stabilizers, provide good light diffusion for your plants. UV treatment also prevents the yellowing effect on the fabric.
For safety purposes, PVC fabric can also be made flame retardant. Another advantage of PVC fabric is that it is easy to install and does not require special skills, so you can quickly set up your greenhouse.
Which Greenhouse Cover Should I Use?
As you read above; Each material has its own unique structure. The light transmittance and thermal insulation values of each are different from each other. On the other hand; cost and durability will also be different for each material.
As a result, the most accurate material; It depends on many different variables such as climatic conditions, investment power, products to be grown, construction of the greenhouse, systems to be used for air conditioning.