The height of the greenhouse skeleton and its related division for more strength as well as controlling the environmental conditions of the greenhouse are very important factors for measures after recognizing the construction site of the greenhouse that should be considered.

Technical issues during the construction of the greenhouse

- It is necessary to observe the technical principles of greenhouse construction by greenhouse companies with related rank and competence from the Organization of Agricultural Engineering and Natural Resources of the province and also to prepare analytical (static) analysis of the proposed greenhouse structure by these companies.
In order to observe the following:
- Suitable foundation according to the climatic conditions of the region (absolute maximum wind speed, wind direction, absolute maximum rainfall and soil texture)
- Greenhouse frame material should be strong and stainless (aluminum, steel and galvanized)
- The use of bolt and nut connections in the construction of the greenhouse is mandatory.
- Development and construction of non-technical greenhouses with wooden frame, single tunnel greenhouses and metal greenhouses with welded joints is not approved.
- The structure must be resistant to wind (at least 120 km per hour), snow load (at least 50 kg per square meter) and load of crop grown inside and cover load (dead and live loads must be observed).
- The height of the greenhouse to the bottom of the gutter should be more than 3.5 meters and to the crown of the greenhouse should be at least 5.5 meters.
- At least 25% of the lateral surface of the greenhouse, including fans and pads, roof and side vents.
- The use of UV plastic coatings in the greenhouse is mandatory.
- Installation of climate control system in order to control at least three factors of carbon dioxide, temperature and light is required.
Note: The technical principles and rules are communicated to the applicant or the contractor by the consultant and the project supervisor, and the applicant is obliged to observe and apply the recommendations of the consultant and the supervisor.

Greenhouse skeleton height and related division

One of the most important factors in the construction of a greenhouse is its height (H). In principle, the height of the greenhouse determines the volume and amount of ventilation (temperature, gas and humidity exchanges) in it. Increasing the volume inside the greenhouse due to its high height causes changes in indoor conditions to occur more gradually than changes in outdoor conditions. And therefore the range of temperature, gas and humidity fluctuations occur less in it. At present, there is a tendency to increase the height in the construction of greenhouses in tropical regions, for better ventilation. Due to the importance of height, this factor, according to the table below, is one of the most important measures and analysis in the division of greenhouses in terms of the use of modern technologies in the world as follows:

A. Low-tech greenhouses - The structure of these greenhouses is traditional (plain metal or wood) and mostly single-span and are covered with a single layer of plastic. The height of the floor to the bottom of the stud (h) is sometimes more than 2 meters and also the height of the floor to the ceiling (H) is sometimes more than 3 meters. Their construction cost is low (minimum necessary cost) and they do not have environmental control devices (heating, cooling, etc.). The level of automation and mechanization used in these greenhouses is very low and pests and diseases in them are mostly controlled by chemical methods. Cultivation in these greenhouses is soil and in most cases, vegetables and ornamental plants are grown in them.

B- Greenhouse with middle technology - The frame of these greenhouses is metal, their cover is plastic (polyethylene) one or two layers, polycarbonate or glass and they are mostly made in several openings. The height of the floor to the bottom of the gutters in this type of greenhouses is 4 meters or less and their height to the ceiling is 6 meters or less. Their construction cost is more than (several times) low-tech greenhouses and they have the means to control the environmental conditions (heating, cooling, ventilation, etc.). The level of use of automation and mechanization is different and acceptable. In this type of greenhouses, pest and disease control by non-chemical method is also possible. Cultivation in this type of greenhouse is open soil (non-rotating) and most vegetables, ornamental plants and fruits are grown in them.

C. Greenhouse with advanced technology - The multi-opening structure of these greenhouses is of advanced metal type and is mostly in the form of Dutch design (Venlo) with glass cover. The curved frame of this type of greenhouse also has a two-layer plastic cover or polycarbonate. In this type of greenhouse, the height from the floor to under the gutters is at least 5 meters and the height from the ceiling may reach 9 meters.

Air exchange and ventilation in these greenhouses are done properly and adequately. The level of use of automation and mechanization to control environmental factors (heating, cooling, ventilation, shading, supplementary lighting, etc.) of this type of greenhouse is advanced and therefore conditions are provided for integrated management of pest and disease control. Cultivation in these greenhouses is non-soil closed (rotating) and all kinds of vegetables, ornamental plants, fruits, etc. are grown in them.

Control of environmental conditions in the greenhouse

Greenhouse The chemical activities carried out in the process of photosynthesis of plants are directly affected by environmental conditions. Photosynthesis depends on factors such as temperature, light intensity, the presence of water and food. Plant respiration varies with ambient temperature. The recommended temperature range for most greenhouse plants, which results in the highest photosynthetic yields, is between 02 and 10 degrees Fahrenheit. Therefore, no matter what the greenhouse is used for, its environment must be controlled; This is essential for the health of greenhouse plants

Strength of greenhouse structures

The structure of the greenhouse must be designed and constructed in such a way that it can withstand all external and internal loads and pressures, including the weight of the frame and the greenhouse cover (dead load), the weight of the product and the equipment hanging on it, the weight of snow and hail and wind force. Is to bear.

Examples of white construction projects in the country