How to choose a polycarbonate greenhouse
Growing vegetables and other crops in sheltered soil for personal needs and for sale promises significant benefits. The best technical and operational characteristics are demonstrated by greenhouses with a metal frame, covered with sheets of cellular polycarbonate. There are many original designs of various shapes and sizes of industrial and own production.If you need a quality greenhouse, but you don’t know how to choose a polycarbonate greenhouse, then our detailed material will help you to solve this difficult task.
Content:
The classical greenhouse is an agricultural construction designed to provide reliable protection of plants from adverse environmental factors. Its basis is a supporting spatial frame of a certain shape. In the construction of greenhouses are guided by the requirements of GOST R 54257-2010, SNiP 2.10.04-85 and SP 107.13330201. These regulations determine the technical conditions and requirements for the design of greenhouses.
For the manufacture of the supporting frame of this structure, a galvanized thin-walled profile or a steel pipe of rectangular or square section is used. Each of the above materials has its own advantages and features that must be considered when choosing it as the basis for the greenhouse.
Galvanized Bent Profile
Galvanized steel profile is light weight and reasonable price. Moreover, its mechanical strength is clearly insufficient, which is offset by the use of a larger number of elements. The connections between the individual parts of the frame need additional reinforcement. Often such a frame consists of many joints, and the metal thickness is only 0.5 - 0.8 mm, which is clearly not enough to withstand peak wind and snow loads.
Galvanized Bent Profile
Galvanized steel frame
Steel profile rectangular or square
The supporting frame, welded from a steel pipe of rectangular cross section, is characterized by durability, high resistance to constant and variable mechanical loads. Its main disadvantage is the tendency to corrosion and the need to protect parts from rust. The frame of the greenhouse is quite complicated to manufacture, which determines the high cost. The arcs of such greenhouses consist of only a few elements, and can even be whole.
Square steel profile
Steel profile greenhouse frame
The choice of material for the construction of the frame is based on the requirements and capabilities of the customer. If you are going to purchase a finished greenhouse, then most likely you will be offered a frame on a thin-walled profile, less often there may be a frame from a profile of rectangular or square section. The best option for strength is a frame made of rectangular or square profiles. The frame from a thin-walled profile will be less durable, but much cheaper and there is a greater chance of running into low-quality manufacturers, which, in order to save money, make the frame not rigid enough.
However, this does not mean that you should abandon such a frame. Just before purchasing such a greenhouse, you need to make sure that it is really durable, and the metal thickness is at least 1.2 mm. As a rule, each seller has samples of frames, you just need not to be lazy to come and carefully consider the options available.If the seller in every possible way hides and does not show samples of frames, there is a high probability that you will be sold a low-quality product.
When choosing a frame, also pay attention to the following points:
- How many elements are made up of arcs, ideally so that they are seamless.
- It is best if the frame profile has a rectangular section of 20 × 40 mm, this is especially true for the base of the greenhouse, because if it is made from a profile with a section of 20 × 20, this may not be enough.
- The thickness of the metal should be at least 1.2 mm., Otherwise there is a big risk that the greenhouse will not stand idle for a long time.
What polycarbonate should be used for a greenhouse
Of great importance for the performance of the greenhouse is the coating. When choosing polycarbonate for a greenhouse, the following parameters must be considered: type of polycarbonate; the presence of a light stabilizing layer; material thickness.
Polycarbonate Type
Today on the market there are two types of polycarbonate - cellular and monolithic. Among these materials, cellular polycarbonate has the best characteristics for use as a roofing material in a greenhouse.
Cellular polycarbonate is a sheet material from the group of thermoplastics, consisting of two or more layers with longitudinal internal jumpers. This plate structure provides excellent technical characteristics and operational properties of the material.
The most significant of them during the construction of the greenhouse are the following:
Low specific gravity
High thermal resistance
High light transmission
High flexibility
Resistance to climatic conditions
High mechanical strength
Technical characteristics that are significant for solving the question of choosing cellular polycarbonate for the construction of a greenhouse are presented in the table:
| Material thickness | 4,0 | 6,0 | 8,0 | 10,0 |
|---|---|---|---|---|
| The specific weight of the sheet, kg / m2 | 0,8 | 1,3 | 1,5 | 1,7 |
| Sheet dimensions, length × width, m | 6(12) ×2,10 | |||
| Thermal conductivity, W / m2 ° С | 3,9 | 3,7 | 3,4 | 3,2 |
| Light transmission coefficient,% | 83 | 82 | 82 | 80 |
| Maximum and minimum temperature, ° C | From - 110 ° С to + 145 ° С | |||
| Service life, years | 10 | 15 | 20 | |
| Minimum allowable bending radius, m | 0,7 | 1,05 | 1,5 | 1,75 |
The presence of a light stabilizing layer
High-quality cellular polycarbonate has excellent selective transmission properties. It almost completely absorbs ultraviolet radiation with a wavelength of 400 nm or less, the most dangerous for plants and transmits visible and infrared rays to the maximum. This helps to create a greenhouse effect.
To protect cellular polycarbonate from the destructive effect of ultraviolet radiation on its outer surface, a layer of light stabilizing substance is applied by coextrusion. You can find out about the presence of such a protective coating by the corresponding inscriptions on the protective film glued to the polycarbonate sheet. You need to be careful here. If there are no special marks on the protective film, this means that they are designed for indoor use.
An attempt to use such materials for the manufacture of a greenhouse will lead to premature failure of the coating. One of the most important properties of polycarbonate is the ability to maintain its technical characteristics throughout the life of the panels. Some manufacturers claim that UV protection is in the bulk of the material. In fact, it is not enough and it is intended only to prevent the destruction of the material during storage.
Cellular Polycarbonate Thickness
When choosing cellular polycarbonate for the construction of greenhouses, the thickness of the sheet is crucial. The specified parameter directly determines such properties of the panels as the light transmittance, the level of thermal conductivity and the ability to withstand mechanical loads. For the construction of greenhouses, sheets are usually used with a thickness of 4 to 10 mm, most suitable for the main parameters.
The thickness of the sheet is determined based on the structural design of the frame, an increase in this parameter increases the resistance to wind and snow loads. In some cases, different panels can be used on the same structure. For flat and arched roofs, sheets of greater thickness are used, and vertical walls are made of thinner panels. The most optimal is the use of cellular polycarbonate with a thickness of 4 - 6 mm. It is necessary to make sure that the panel thickness declared by the manufacturer is actual. To do this, the panel can be measured with a caliper. If the declared and actual thickness of the polycarbonate sheet does not match, the use of such material should be discarded.
In no case do not agree to buy polycarbonate with a thickness of 3.5 - 3.7 mm. At the same time, sellers may say that this material has a higher density, so it can be used instead of sheets with a thickness of 4 mm. But most likely it is low quality polycarbonate, which has an extremely low service life.
If polycarbonate easily bends from the effects of fingers and does not have a designation on which side the light-stabilizing layer is located, then this is a cheap material that has a service life of no more than 2 years.
In the process of choosing cellular polycarbonate for the construction of a greenhouse, special attention should be paid to the following points:
- Correspondence of the panel thickness declared by the manufacturer and indicated in the documentation and on the package.
- The presence of a protective film on both sides of the sheet, which protects them from premature wear.
- Availability of accompanying documentation for the entire batch: certificates of conformity for products and passports.
Determine the shape of the greenhouse
There are several varieties of agricultural structures of this kind.
Their main types can be classified as follows:
Arched greenhouse
Arched greenhouse is a structure with a semicircular overlap. The spatial frame consists of arcs located at a certain distance from each other with transverse connecting elements. This type of greenhouse is most prevalent among the population. The structure can be quite easily increased or decreased in length. This is done by adding or removing individual sections.
Arched type greenhouse with lifting sides (butterfly greenhouse)
Such a structure has a rather modest size and is more likely a greenhouse, its main convenience is the possibility of easy access to the garden and the organization of ventilation of the internal space if necessary.
Greenhouse with a drip arch shape
Consists of two curved surfaces connecting line, which forms an acute-angled ridge. Such a device prevents the formation of snow on slopes. An additional stiffener ultimately helps to increase the strength of the structure.
Photo: jrmk.net
Shed or wall greenhouses
The simplest structure, which uses the building envelope of residential or office buildings in personal plots as a supporting structure. During construction, a sufficiently large slope angle to the vertical is specified, which prevents the formation of a stable snow cover on the surface. The facility is located on the sunny side of the building to maximize the use of natural light.
Gable Greenhouse
The gable classic greenhouse before the appearance of plastic polycarbonate was the only possible form. In appearance, it resembles an ordinary house with vertical walls and a flat roof. The simplicity of the design makes it possible to manufacture it without the use of equipment for arching arches for the arch frame. This design can be built from any materials, including wood.
Photo: www.as-superstore.at
When choosing the form of a greenhouse, the owner is guided by several factors, primarily its purpose and its own financial capabilities.For growing seedlings, a small wall structure or a greenhouse with lifting walls will be enough. Vegetable production will require solid arched or gable greenhouses with corresponding costs.
Dimensions of the greenhouse and individual elements
When determining the size of a greenhouse, its purpose and planned production volumes are primarily taken. Design work, even in the most simplified version, allows with sufficient accuracy to calculate the required amount of materials.
General rules for the implementation of such events are as follows:
- It is necessary to establish the length, width and height of this structure. This takes into account the area and configuration of the site and the convenience of work in the greenhouse.
- The angle of the roof slope is determined, which ensures spontaneous sliding of snow.
- When determining the size of the doors, it should be borne in mind that a person will carry tools and agricultural implements during the execution of work. In addition to the entrance to the wall, a folding transom is provided for ventilation of the structure.
- The frame device should be such that the joints between the individual sheets of polycarbonate should fall on its elements. This approach allows you to significantly strengthen the design.
Fixing the structure to the foundation
The vast majority of greenhouses have a relatively light construction and significant windage, and can be turned over by the wind. Polycarbonate greenhouses must be carefully fixed to the base, which can take the form of a strip foundation with a brick or stone base. The device of such a supporting structure requires significant investment and is used only for large enough stationary greenhouses.
The mounting of the supporting frame to the foundation is carried out through the use of embedded elements. Steel pipe structures are usually welded to special metal parts embedded in the base. Galvanized steel frames are fastened to masonry using dowel nails or anchor bolts. The latter installation method is more reliable.
The question of choosing a polycarbonate greenhouse comes down mainly to determining its size and shape based on its purpose and the capabilities of the owner. High-quality construction must be correctly installed on the site, which will ensure its long-term operation.
