Comprehensive article on greenhouse construction - Different types of greenhouses - Greenhouse maintenance
The growth of greenhouses prompted us to publish a story about greenhouse structures and familiarity with the construction of greenhouse types and generally familiarity with greenhouse cultivation, I hope that in addition to being effective in formulating your justification plan, it will give you useful information about your loved ones and investors in the agricultural sector.
The greenhouse is a place to cultivate plants. Covered by transparent coatings. Yath greenhouse cover creates a greenhouse effect and locks solar energy into the greenhouse. Greenhouses that vary in size protect plants from excessive winter cold or excessive summer heat.
Each plant needs special conditions in terms of light intensity, daily temperature, night temperature, relative humidity of air and soil moisture in order to have optimal growth. For the production and commercial breeding of high-quality plants and all year round, optimal environmental conditions should be controlled by damage factors such as wind, devastating storms, cold and frost, etc. We are through a building called greenhouse which is considered as a controlled environment and due to the increasing market needs, both in terms of production of flowers and ornamental plants and in terms of vegetables and off-season, this method of production has become one of the most profitable agricultural sectors today, which of course demands a lot of initial investment. Due to the great investment in this field, lack of proper management in greenhouse construction, selection of location, type of greenhouse and its coverage will lead to lack of proper productivity of capital and facilities.
Definition of greenhouse
Greenhouse or Green house refers to a limited space that can control the suitable environmental conditions for plant growth from different regions during different seasons of one year. According to this definition, including greenhouse performance, providing the necessary environmental conditions is a specific product requirement. Greenhouses are divided into fixed and moving types depending on what type of building materials are used in them. Fixed greenhouses are greenhouses in which the building materials used are of stable and durable materials. So they should be used for many years.
Introducing the divisions of greenhouses
Greenhouses have different types in terms of type of lyde and type of structure type as follows:
Division by type of production
:: Vegetable and vegetable greenhouses include products such as mink, tomato, strawberry, pepper, eggplant, cantaloupe, vegetables (rayhan-cress, etc.).
:: Greenhouses produce flowers and ornamental plants to produce a variety of cut flowers (Rose- Gerbera - Glyol - Davoodi) and apartment flowers.
:: Greenhouse halls produce button mushrooms and shellfish mushrooms
Types of greenhouses in terms of land use
The greenhouse is divided into four categories based on the type of use and its use:
- Teaching Greenhouse (GREENHOUSE)
- Research Greenhouse (RESEARCH GREENHOUSE)
- Recreational and Entertainment Greenhouse (HOBBY GREEN HOUSE)
- Commercial GREEN HOUSE
1- Educational Greenhouse (TEACHING GREEN HOUSE)
The main purpose of the construction of these greenhouses is to train the planting, harvesting and management stages of the greenhouse to trainees and students, so the greenhouse should have soil and hydroponic cultivation facilities, this greenhouse should have all the standards of the commercial greenhouse and the trainee should be trained with real working conditions. The distance between the culture rows for trainees is more than other greenhouses. These greenhouses are equipped with all accessories, heating, cooling, irrigation and temperature control systems, humidity, CO², etc. is. The equipment has the lowest noise pollution and the greenhouse space is as beautiful and attractive as all educational places.
The educational greenhouse should be usable in all seasons of the year, the type of suitable coating for these greenhouses is from glass or polycarbonate sheets, in no way is polyethylene coatings (temporary coating) recommended. The cost and return of capital are also not desired.
2- Research Greenhouse (RESEARCH GREEN HOUSE)
The purpose of this type of greenhouses is to investigate and modify the genetic structure, tissue culture, effect of temperature, light, CO², moisture, growth conditioning, investigation of microbial, viral, fungal and pests and diseases in flowers and plants, so controlling environmental parameters is different from other greenhouses. The installation of the side window and ceiling should be such that there is no gap between the window and its installation location.
* Equipped with automation systems
* Windows are equipped with anti-insect nets.
* Usually the area of this type of research greenhouse is 250 to 500 square meters.
* Coating of glass or polycarbonate sheets
* Usually the type of cultivation, hydroponic and on the platform is done.
* The cost of constructing this type of greenhouse is very high.
3- Hobby GREEN HOUSE
These greenhouses are mostly used to store household ornamental pots and shrubs. The beauty of the frames of these greenhouses is of particular importance because of their use in open spaces of houses or gardens, the area of these greenhouses is small except for those that use the space inside it for reception or rest.
The main skeleton of these greenhouses is mainly galvanized iron and its coating is also made of glass or polycarbonate sheets.
4- Commercial GREEN HOUSE
The objectives of building a commercial greenhouse:
Production of off-season outdoor production products
Maximum production per unit area
Reducing the cost of production per unit area compared to outdoor production
Optimal use of agricultural institutions (water, seeds, fertilizers, pesticides, etc.)
Hydroponic culture method (hydroponics)
Pest control, pollution, diseases
Using land that cannot be cultivated open.
Ability to compete with low risk in the market
According to the type of product to produce the greenhouse structure is determined.
The minimum area that has economical and cost-effective justification is 5000 square meters and for an area above 5000 square meters, we need to control more environmental parameters (light, temperature, CO², ventilation, humidity and aphthous and diseases).
Types of greenhouses based on appearance
1- Gable Roof (A Frame)
The presence of angles in the crown of this type of greenhouse, which resembles the word A, is the reason for the naming of this model. This steep slope leads snow and rain to the studs and also directs the transpiration inside the greenhouse to the sides and on the other hand, causes the failure of light rays into the greenhouse for the use of maximum light radiation. Due to the high weight of glass compared to other coatings and also the low dimensions of glass, the distance of columns and bows from each other is low, the weight of the structure per unit area is high, so the structure is heavy and expensive. Structures are usually constructed in windy areas and high annual snowfall. Glass heat transfer coefficient is high compared to other coatings, which is one of the disadvantages of this structure. To resolve this defect, double glazed coatings of polycarbonate sheets can be used, which requires more cost.
The coating of these greenhouses is due to the following reasons:
* High passing coefficient of light
* Operation in four seasons of the year
2- CURVED ROOF
Reasons for using arched ceilings
* The requirements for a good greenhouse are sufficient volume and space because the more volume and space of a greenhouse, the better the rotation of air in the greenhouse, and therefore co² is required to perform photosynthesis in sufficient amounts to be provided to the plant.
* Reduce the level of heat exchange
* Compatibility with different climates
* Reduce fuel consumption
* Possibility of construction in large area
* How to assemble bolts (portable)
In arched ceiling structures, polyethylene coatings (nylon) are installed in less time and easily screwed into structures by polylak, these roofs show the least resistance to wind because of their aerodynamic appearance. The low weight of polyethylene coatings (nylon) as well as the resistance of these structures against wind and snow makes the weight of the structure per unit area less, so the price of the arched roof structure is lower than the gable roof structure (A frame). Other advantages of low heat exchange polyethylene coatings as well as the special properties of Anti Fog and Red light, which will be explained in detail in the greenhouse coatings section.
The ability of other tunnel structures is to double the structure and inject compressed air into it, which reduces fossil energy consumption by 40% and significantly solves the perspiration problem.
In multi-span greenhouse structures for easier cultivation and traffic and optimal use of all surfaces, the arch is installed on vertical columns.
Two things can be mentioned as a specific flaw in these types of greenhouses:
1- The greenhouse cover level at the highest point is horizontal and this leads to the lack of proper guidance of snow and more importantly humidity and sweating at that point, this defect is elevated by using two structures or changing the arch ceiling to the dome, of course, methods such as controlling humidity with increasing temperature are also used to reduce moisture inside the greenhouse.
2- The second problem of these greenhouses is in ventilation. It is more difficult to construct a window system for these types of greenhouses than A Frame greenhouses. Considering that natural air conditioning is one of the most important items of commercial greenhouses to reduce the cost of temperature and humidity control, therefore, proper implementation and efficiency of this system is very important.
Methods such as the use of skylights in different models in these types of greenhouses are implemented.Ventilation with side windows (ROLL UP) is also used for more efficiency in commercial greenhouses.
The construction of a window with high ventilation level and its use at the highest point of the structure is one of the advantages and parameters that the manufacturers emphasize on.
3- Domed Ceiling Greenhouse (GOLHIC ARCH)
The basis of the greenhouse with a domed roof for the use of tunnel greenhouses is with the aim of resolving the two defects of the arched roof greenhouses. In this plan, the greenhouse crown will be from arch to gable greenhouse, so in this plan we will have all the benefits of tunnel greenhouse along with solving the problems of the arched roof, this high-rise design is used in tunnel greenhouses with high widths.
Types of greenhouses in terms of structure
In terms of the type of structure, greenhouses are divided into two categories: wood, traditional, modern or metal.
The main skeleton of these greenhouses is from plastic-coated wood. The height in these structures is 2 to 3 meters and the heating and ventilation system is not suitable and due to low height, it is not suitable for the production of products such as minced and tomato. The advantage of these greenhouses is the cheap price of constructing each unit, but due to inappropriate internal environment for plant growth, usually the amount of production per unit area is much lower than modern greenhouses. For the mentioned reasons, these greenhouses have not been developed and the previously constructed wood greenhouses are gradually converted into modern greenhouses.
Metal or modern greenhouses
The skeleton of these greenhouses is made of metal, which is usually coated with uv-proof plastics and has a suitable heating and ventilation system. The height of these greenhouses is more than 4.5 meters and due to suitable plant growth conditions in this structure, yield per unit area is higher than wood greenhouses.
The connection of parts in metal greenhouses is by screwing (portable) or using welding. The cost of portable greenhouse unit is 15-20% higher than boiling system, but it is easier to install and changes in the structure are easier. Different parts of existing structures, advantages and disadvantages are shown in the table below.
Low production - Many pests and diseases and life
Increase fuel consumption
Low pollution and long life.
Tunnel: Single Unit
Good ventilation, automatic.
Very expensive, high fuel cost.
High sturdy, long life, good ventilation – ibility
Side - Ceiling
Greenhouse halls produce edible mushrooms
Edible mushroom production workshops with blocks, bricks, cements are constructed as a normal building in which heating, cooling and dehumidifier facilities are embedded.
Some workshops for fungal production are constructed as greenhouses, but considering that the growth of the fungus requires a small light. Greenhouse coatings are selected from the type of colored plastics that a small light should pass through.
Edible fungi that are grown in Iran include button mushrooms and shellfish fungi, the production of button mushrooms in addition to breeding halls requires compost production workshop which produces compost contamination of the environment. Therefore, these workshops should be constructed outside of residential areas with the permission of the EPA.
The shellfish fungus breeding bed is a reduction in grains and because it does not require compost, it does not cause environmental pollution and can be grown in residential areas and does not require EPA permission.
Types of greenhouses in terms of coverage
Plastic coatings can be made of polyester, polyvinyl chloride (P.V.C) polyvinyl fluoride (P.V.F). One of the advantages of these coatings is the lack of need for heavy skeletons and a drop in the cost of heating up to about 40% compared to one-layer glass greenhouses.
Most plastic coatings are polyethylene, usually mixed into UV resistant materials (UV rays), in which case their lifespan can be extended to about 3 years. Today, in advanced countries, polyethylene and other coatings mix plastics into infrared light preservatives (IR) that reduce greenhouse temperature losses by 15 to 25 percent at night.
PVF is also a new plastic coating that lasts up to ten years and its reaction to light and its price is almost equivalent to glass.Plastic double coatings also reduce the cost of fuel.
Up to one-third have an effective role. Today, practically all modern greenhouses with plastic coatings use a compressed air system between the two layers. 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 0.102mm thick because U.V. light is less in place.
Glass greenhouses are one of the most costly types of industrial greenhouses. The need for a solid skeleton as well as the use of glass coatings as well as high fuel consumption in these greenhouses have increased the price of these greenhouses compared to plastic and polycarbonate. The advantages of these greenhouses are the high ability to pass light and sun heat, which are highly efficient in cold and low light areas. Glass greenhouses also have the highest lifespan compared to other types of greenhouses, which is also higher than other types of greenhouses.
One of the advantages of polycarbonate coating instead of glass is the lower cost and lighter weight. Also, its high resistance to plastics has led to its increasing demand as a coating in greenhouse industry. Polycarbonate coating is often intended to cover the front, rear and semicircle parts of the corresponding or the sides and roof of the greenhouse if the customer demands. Polycarbonate sheets are a good alternative to glass and save energy. So that in summer they prevent heat from entering and in winter they prevent the exit and wasting of heat inside.
FAO Greenhouse Plan
In the project that the organization has introduced for greenhouse structures, all the greenhouse skeletons are prefabricated and without the use of any welding and all galvanized iron metal and are assembled by bolts and clamps.
The height and width of the crater vary according to the type of planting and this structure engineeringly must necessarily be resistant to wind at 120 km/h and snow weight up to 80 cm height (if the heating system is on). In this structure for proper ventilation, side windows with a height of 1.5 meters on the sides and pad and fan system at the beginning and end of the greenhouse and a nationwide skylight are placed exactly at the head of the bow. To cover this structure, anti-UV plastic (at least 3% effective material) and antiperspirant and in cold and dim places, double glazed polycarbonate coating (minimum double glazed distance of 8 mm) is recommended. In order to maintain temperature and energy, this structure is interconnected and even as much as possible is a fabric with a close length and width (approximately square shape).
In the article of the plan to justify the production and cultivation of roses in hydroponic greenhouses, you will find appropriate information about these greenhouses.
Description with the conditions of greenhouse construction
Greenhouse Construction Site
One of the first decisions to be made is for the greenhouse to be built as a separate unit, in contact with existing buildings or as part of new buildings. Interconnected greenhouses typically have lower construction and heating costs and easier access, but plants get less light. Interconnected greenhouses must be built facing the south. An independent greenhouse can be built in a place farther away from existing buildings. Plants in such a greenhouse receive sunlight from all directions. These greenhouses are very expensive in terms of construction and thermal system and require tremendous costs for water and electricity lines. A greenhouse can be built in any size but the smallest greenhouse that can be considered is about 200 square feet (18.4 square meters). Smaller greenhouses are very expensive in terms of construction and performance. The issues that should be considered for greenhouse construction are:
Access to transportation routes that are minimized by constructing as much as possible closer to the main roads of this problem. The type of fuel consumed in the greenhouse, in areas where natural gas is available, can be used to reduce the costs to a large amount in the production of cold season.
Access to water resources with good quality and quantity.
Environmental impacts, where it constantly has inclement weather, heavy rains, shade caused by being located on the northern slopes of high mountains or skyrocketing trees, is not suitable for greenhouse construction. Light intensity is one of the determinants.
The type of product that is placed in the production schedule. Considering that the trends are towards the specific production of products and the production agenda is determined after the initial study of the domestic and foreign market, before construction, they must first determine what product is produced and then decide to construct a greenhouse in the region and the appropriate climate of the product. *Considering the laws regarding the land of urban areas and the construction and operation of greenhouses and....
The construction site should be as flat as possible because in case of roughness and steepness, creating a large greenhouse will be accompanied by many problems and costs for leveling.
Direction of greenhouses
The greenhouse skeleton creates shadows and varies according to the angle of radiation of these shadows, it is important to pay attention to this, especially in winter production, because few changes in the percentage of light reached to plants can play an important role in the quantity and quality of production. The position of the greenhouse should be such that it receives the highest amount of light. The first choice for the position of the greenhouse is in the form of a south or southeast view. All-day light provides the best conditions for the plant.Of course, the light shining from the east, in the morning, is sufficient for plants. Morning light is the most desirable, as plants are allowed to start the process of food production earlier. And this leads to maximum growth. Naturally, the next choices are the southwest view and the western view, because the light is received later. The northern façade is the least desirable and is only suitable for plants that require little light.
Deciduous trees such as maple and oak can effectively reduce intense summer light by creating shade. Of course, it should be noted that trees do not shade the greenhouse in the morning. These trees allow enough light to reach the greenhouse in winter, as they lose their leaves in autumn.
Airflow in the greenhouse
Air circulation in the greenhouse is essential. When a plant is exposed to fresh air flowing outside the greenhouse, fresh air is provided near the leaves and the plant can back oxygen and use fresh carbon dioxide. Airflow also helps to keep relative humidity low and temperature control in the greenhouse. Commercial greenhouses depend on all the requirements mentioned above and even more. In a commercial greenhouse, the main goal is profitability, in order to achieve this goal, the greenhouse must be efficient in terms of providing favorable environmental conditions. The light and temperature of the greenhouse must be strictly controlled. Computers have been widely used for such controls recently. Also, the presence of toxic gases and dust in the greenhouse may be a serious problem. These gases include carbon monoxide, nitrous oxide and nitrogen dioxide, which may be emitted by thermal devices.
Control of greenhouse environmental conditions
Chemical activities performed in photosynthesis process of plants are directly affected by environmental conditions. Photosynthesis depends on factors such as temperature, light intensity and the presence of water and food. Plant respiration is different from environmental temperature. The recommended temperature range for most greenhouse plants leading to the highest photosynthetic efficiency is between 50 and 85 degrees Fahrenheit. Therefore, no matter what the greenhouse is used for, its environment should be controlled, which is essential for the health of greenhouse plants.
Temperatures in greenhouses
Setting temperatures in greenhouses is the primary condition for the growth and development of many plants. Plants need different temperatures. Some plants require higher temperatures, such as tropical plants. Others grow well at temperatures below 20 degrees Celsius, such as plants that are isolated from cold regions such as primrose, which can be seen in the forests of the north. But how temperatures are regulated in greenhouses depends on the heat system. Types of heaters or gas systems and ... can be used. Thermal systems must be able to distribute temperature uniformly and have no environmental impact. Recommended daily and night temperatures for several common greenhouse products, overnight temperature product (F) daily temperature (F) tomato 66-60 80-70 lettuce 55 78-70 cucumber 65 80 peppers 62 80-70 chrysanthemum 63-62 80-75 geranium flower 60-55 75-700
Optical requirement of plants
Not all plants need light at the same size.
Plants are divided into three groups in terms of optical requirement.
:: Long day plants LDP: Long Day Plants need light for between 10 and 14 hours to flower, such as seasonal summer plants such as ahar, atlases, cute and monkey.
:: SDP Short Day Plants: Short Day Plants need less than 12 hours to flower. They are placed in the opposite side of the plants of the long day, like chrysanthemums.
:: Plants indifferent to day length NDP: Neutral Day Plants are very suitable for home maintenance. Like henna flowers or begonias that are not allergic to day length and have flowers all year round.
Water Yari Greenhouses
Moisture supply is one of the most important parameters for plant growth and development. After recognizing the moisture requirements of plants, we replace them in our own greenhouses, i.e. not all plants are kept in the one type of greenhouse. At large and specialized levels, each greenhouse is considered for a product or a number of similar products with the same requirements.
A variety of irrigation methods are briefly as follows.
Surface irrigation (gravity): Surface irrigation systems have low efficiency and water loss is high. At the same time, it washes salts, increases weed growth and causes a variety of fungal, parasitic and decay diseases. These systems are implemented in the form of curtie and tape irrigation.
1- Sprinkler irrigation: The purpose of sprinkler irrigation is to distribute water uniformly to all plants and reduce ambient temperature and increase moisture. Water use efficiency is 75 percent. The initial cost is a lot of disadvantages of this system. 2- Drip irrigation: In this method, water, chemical fertilizers and other materials required by the plant are provided solublely by emitters installed on the side pipes. The water use efficiency is 90% and since emitters are located next to the plant plant or stem, the possibility of weed growth and development disappears.
Carbon emissions in greenhouses
The application of Co2 is almost equivalent to the use of food. In Iran, where plants are in good light condition, the efficiency of the crop can be increased by increasing co2 consumption. Co2 is essential for photosynthesis. This chemical reaction leads to the production of a green product. Co2 is a very important factor in this reaction. For many years, sources of carbon dioxide enrichment in greenhouses have been discovered to increase plant growth and production. Carbon dioxide is one of the most essential components of photosynthesis. Photosynthesis is a chemical process that uses sunlight energy to convert carbon dioxide and water into sugary substances in green plants, then these sugars are used during plant respiration to grow it. The difference between photosynthesis and respiration rates is the basis for dry matter accumulation in plants. In greenhouse production, the goal of all breeders is to increase dry matter and economically optimize crops. Carbon dioxide increases crop fertility due to improved plant growth. Some of the cases where crop fertility is enhanced by carbon dioxide enrichment include: preterm flowering, higher fruiting efficiency, reduction of incomplete buds in flowers, improvement of plant stem strength and flower size. Therefore, plant breeders should consider carbon dioxide as a nutrient.
One of the important issues in the construction of a greenhouse is paying attention to greenhouse drainage. In areas with hard textured lands with impenetrable surface layers, by placing vented clay pipes of substructurds or in other innovative ways, they are considering necessary measures to improve drainage.
In windy areas, a row of trees or a natural barrier such as a hill is used to reduce wind damage. The minimum distance of trees from greenhouses in the east and west should be about 2.5 times the height of trees. This distance in the southern part is more than one height of trees.
Platforms and substrates
The platform is part of the greenhouse space, a place for pots or plant cultivation in substrates above the ground, as the name suggests, platforms are always placed at a level above the greenhouse floor. This action, while preventing the spread of plant-borne and pathogenic agents, helps to better ventilate and warm the bed earlier. The choice of the shape of the platforms and their ingredients depends on the type of plant, greenhouse and the taste of the manufacturer. In general, the features of a good platform are:
A- Have good drainage.
b-The width is such that the workers have easy access to the platform center.
C- Installed to absorb maximum light. Working with rigs to put pots allows workers to do their job without bending, while the rigs are better used to cultivate plants 30-15 cm deep and have good drainage. The height of the platforms from the ground level should be such that the measures should be possible with the worker's dominance of the product, which depends on the type of product. Platforms can be made of aluminum, Iranian, wooden timber or concrete materials. Aluminum has a long life, but it is expensive and wood is inexpensive, but it has a short life and the probability of decay is high and pathogens also penetrate it. How the platforms are located should be installed so that the maximum greenhouse space should be used for plant breeding. The number and width of the corridors depends on how they are used and the type of product. The height of the cultivation platforms is 80-90 cm. The width of the platforms adjacent to the walls is about 90 cm and the width of the middle platforms accessible on both sides should be at most 180 cm. The cultivation platforms of pot plants should not be walled and the floors of the platforms should be as vented as possible. Perforated wooden boards with tight thoracics are suitable for building the floors of platforms. In the new method, moving platforms are used to effectively use the maximum greenhouse space. This system increases production space up to more than 90% of greenhouse area. The corridors are occupied by moving platforms, which open the corridor from one side and close on the other.