Types of greenhouses in terms of structure

According to the type of structure, greenhouses are divided into two categories: wooden or traditional and modern or metal. Wooden greenhouses The main skeleton of these greenhouses is made of wood with plastic covering. The height of these structures is 2 to 3 meters and it does not have a proper heating and ventilation system, and because of the low height, it is not suitable for growing crops such as cucumbers and tomatoes. The advantage of these greenhouses is the low cost of building each unit, but due to the unsuitable indoor environment for plant growth, the amount of production per unit area is usually much less compared to modern greenhouses. Due to the mentioned reasons, this type of greenhouses has not been developed and the wooden greenhouses that were built before are gradually turning into modern greenhouses.

Metal or modern greenhouses The skeleton of these greenhouses is made of metal, which is usually covered with anti-ultraviolet (UV) plastics and has a suitable heating and ventilation system. The height of this type of greenhouses is more than 4.5 meters and due to the suitable conditions for plant growth in this type of structure, the performance per unit area is increased compared to wooden greenhouses.

Connection of parts in metal greenhouses is by screw and nut (portable) or using welding. The unit cost of portable greenhouses is 15-20% more than the welding system, but its installation is easier and changes in the structure are easier.

Plastic Plastic covers can be made of polyester, polyvinyl chloride (P.V.C), polyvinyl fluoride (P.V.F). One of the advantages of these covers is that there is no need for heavy skeletons and the reduction of heating costs by about 40% compared to single-layer glass greenhouses. Most of the plastic covers are of polyethylene type, which are usually mixed with UV resistant material, in which case their lifespan can be increased up to 3 years. Today, in advanced countries, polyethylene and other plastic coatings are mixed with infrared light (IR) preservatives, which reduce greenhouse temperature losses by 15 to 25 percent at night. PVF is also a new type of plastic coating that lasts up to ten years and its reaction to light and its price is almost equivalent to glass. Double plastic coatings also reduce fuel costs. Up to one third have an effective role. Today, practically all modern greenhouses with plastic covers use an interlayer compressed air system. Two layers of plastic, one of which is placed directly on the outer surface of the other sheet, are separated from each other by a cushion of compressed air. The outer layer of plastic must be 0.152mm thick to reduce ultraviolet (U.V) light, while the inner layer only needs to be 0.102mm thick because the U.V light is less in this place. Glass Glass greenhouses are the most expensive type of industrial greenhouses. The need for a strong frame and the use of glass cover as well as high fuel consumption in these greenhouses have increased the price of these types of greenhouses compared to plastic and polycarbonate. Among the advantages of this type of greenhouses, we can mention the high ability to pass light and heat from the sun, which are highly efficient in cold and low-light areas. Also, glass greenhouses have the longest lifespan compared to other types of greenhouses, which, of course, have higher maintenance costs than other types of greenhouses. Polycarbonate Among the advantages of polycarbonate coating instead of glass is its lower cost and lighter weight. Also, its high resistance compared to plastic has caused its increasing demand as a coating in the greenhouse industry. Polycarbonate coating is often considered to cover the front, back, and semi-circles, or the sides and roof of the greenhouse if requested by the customer. Polycarbonate sheets are a good alternative to glass and save energy. So that they prevent the heat from entering in the summer and prevent the heat from leaving and wasting in the winter.