A greenhouse project is a major one, and a few key considerations decisions need to be made right at the beginning of the process. A major part of how to build a greenhouse would be based on your needs and, of course, the budget. You will come across several cheap greenhouse kits in the market for greenhouse farming. However, before making any purchases and buying equipment, you need to be sure as to how you are going to use it so that the greenhouse functions the best for your needs. You may be looking for a permanent greenhouse or a portable structure. Keep in mind aspects like the right size, maintenance, and the right covering. Once you have gone through those aspects and are clear on your needs, you can proceed confidently.
How To Build A Greenhouse
Before you start looking for good quality and cheap greenhouse kits, you should know the basic and what goes behind the building of the greenhouse.
· Location of the greenhouse
To begin with, you need to be sure about where you want the greenhouse to be. Wherever you decide to build the greenhouse, make sure that it gets ample sunlight. As the food production in the plants begins early, the morning sunlight is most desirable for maximized growth. The greenhouse can get shaded from the intense afternoon summer sun under the deciduous trees. Avoid placing the greenhouse under Evergreen trees that have foliage all year round.
· Good drainage system
When considering how to build a greenhouse, it is essential to building the greenhouse above the surrounding ground so that any rainwater and irrigation water can drain away easily.
· Convenient workplace and utilities
Other site considerations to focus on are sources of heat, the requirements of the plants, shelter from winter wind and sources of water and electricity. There should be a convenient workplace for storage area as well as potting plants.
· Floors of the greenhouses
Permanent flooring is not recommended as it may stay wet and slippery. Poured concrete, brick, or block foundation is preferred. It is essential to get a stone or gravel walkway for easy access to the plants. It is best to spray water on the gravel to produce humidity in the greenhouse. In case, you plan to build a permanent floor, make sure it carries an anti-slip surface plus good drainage.
·Glazing for light transmission
Look for good quality cheap greenhouse kits that carry sheets for the glazing materials. Polycarbonate comes with a warranty against yellowing, hail damage and getting brittle. Polycarbonate is a multiwall material with good durability, and the only downside is the clarity of vision.
· The requirements of heating
When learning how to build a greenhouse, you need to focus on the heating needs. The heating necessities will be influenced by on the location of the greenhouse, the required temperature for plants grown, and the outside exposed area of the structure. About 25 percent of heat requirement get supplied by the sun. However, a lightly insulated greenhouse will need a heating system to maintain the desired temperatures. Solar-heater greenhouses can be a good option but are not economical to use. It is essential to keep the greenhouse air temperature comfortable for the plant growing temperatures.
How to calculate the heating system
When you look for information on how to build a greenhouse and are looking for cheap greenhouse kits, it is essential to get information on the calculating heating system. Heating systems are rated in Btu or British thermal units and is summarized as the following equation:
Q = A x U x (Ti – To)
Q is the Btu of a heating system.
A is the entire exposed area of a greenhouse sides, ends, the roof.
U is the heat loss that enumerates the rate of heat energy flow out of the greenhouse.
(Ti – To) is the maximum difference between the lowest temperature outside (To) and the temperature to be preserved in the greenhouse.
The above technical discussion must be considered when making a greenhouse and the effect of each value on the outcome. The heat loss for different materials used in the construction to the walls and roof must be calculated. Unvented heaters are not suggested and a fresh air inlet is essential when using wood, gas, or oil in the greenhouse.
Circulation of Air
It is a good investment to install circulating fans in the greenhouse. After all, you need to maintain air flow during the winter when the greenhouse is heated and ensure that the temperatures remain unvarying throughout the greenhouse. Without the air mixing fans, the warm air rises towards the top and the cool air descends on the floor. Those mixing fans keep the air circulated and at a uniform temperature. You can get small fans with a capacity of moving a cubic foot per minute of air. Place the fans in opposite corners diagonally for about 60 feet long greenhouses. The aim should be to develop a circular air movement. However, during the summer, turn the fans off during when the greenhouse needs proper ventilation.
Cooling and Ventilation
Cooling and ventilation are essential in a greenhouse even in cold weather. It can get too warm for the plants on a sunny day. Ventilation ensures proper exchange of air and a control over the temperature as well as replenish carbon dioxide and remove moisture. Several ventilation systems can be used. For example, the natural ventilation makes use of the roof vents on the ridgeline, carrying louvers or the side inlet vents. Warm air rises and escape through the top, thus drawing cool fresh air through the sides. In the case of Mechanical ventilation, the exhaust fans move air out from one end and allows the outside air to enter the other end with the help of motorized louvers. The exhaust fans should be of the right size to allow a complete exchange the total volume of air in the greenhouse every minute. These are essential aspects on how to build a greenhouse.
Calculate the total volume of air in a greenhouse by multiplying the floor area times 8. The exhaust fan capacity is estimated by multiplying the floor area by 12. The rating of the static pressure accounts for air resistance through the fans and louvers. The exhaust fan capacity should be chosen at one-eighth of an inch static water pressure.
The ventilation requirements will vary with the different season and it is essential to know how much of the greenhouse will be used before making arrangement for the ventilation and cooling. During the winter, just 20-30 percent of air volume exchange per minute is adequate without chilling the plants. Two-speed fans are better as one single speed fan will not be able to meet this criterion. You can use a combination of a single speed fan, plus two-speed fan that create three ventilation rates to meet year-round needs with the help of stage and two-stage thermostat.
You need to keep an eye on the capacity of the fans and how a two-speed motor on low speed delivers at its full capacity. The ventilation capacity will be different for winters and different in summer. Do not take any shortcuts when developing an automatic control system for ventilation in greenhouses.
How to keep the greenhouse cool in the summer?
An essential aspect regarding how to build a greenhouse is to how to keep it cool during the hot summer season. When looking for cheap greenhouse kits, ask about the shade cloth, which is one of the most significant elements to keep a greenhouse cool in the summer. The shade cloth can be fastened on grommets on the outside with rope or installed inside with the help of wires. You can use a roll up and down system for the shade cloth that allows 30- 90 percent light transmission. An efficient heat reduction can be ensured with the outdoor installation. However, it interferes with the vents. Blinds can be used in place of the shade cloth, but they interfere with the vents on the outside. The blinds can be adjustable on the inside. A properly planned ventilation system should ensure 3 to 4 degrees of the outside temperature inside the greenhouse.
There are Misting systems available for cooling or raising the relative humidity (RH) in the greenhouse. RH is the measure of water dissolved in the air at a particular temperature and is shown as a percentage. Most plants remain relatively unaffected with a range of RH between 45 percent and 85 percent. However, if RH dips below 45 percent, the growth rate slows down, and the plant develops smaller leaves or burned leaf margins. If RH levels rise above 85 percent, the plant becomes susceptible to fungal pathogens. Thus, one should be aware of those issues caused by several conditions and by high or low RH, when they learn how to build a greenhouse. Those RH levels can get reduced to unacceptable levels during the summer, high temperature, high light and rapid air movement due to fans. You should keep the greenhouse full of plants as they generate a lot of RH. Go for Shading to lower light and temperature and use misters or evaporative cooling as the best solutions.
What is Evaporative cooling system?
When looking for cheap greenhouse kits, you will come across Evaporative cooling systems available in two configurations, one with fan and pad and other as a small package evaporative coolers. The evaporative cooler works at an optimum level when the outside humidity in the air is low.
The small package evaporative coolers carry a fan and pad to evaporate water. The system cools the air and increases humidity. The heat removed from the changes the water from liquid to a vapor. The cooler moist air enters the greenhouse and increases the humidity as the heated air moves out through roof vents or louvers. The alternative package system is used in commercial greenhouses. The pads are placed on the air inlets at one end of the greenhouse. The exhaust fans are used at the other end of the greenhouse to pull air.
It is seen that the moisture content of the atmosphere remains constant on a hot sunny day. It means that during the afternoon when the temperature is at its highest, the RH is lowest. The lower the humidity, the better will be the evaporative cooling effect. Thus, the cooling effect is best when you need it the most. You should keep the evaporative cooler capacity at 1.0 to 1.5 times the volume of the greenhouse. With a properly designed system, you can lower the temperature inside the house by as much as 10 to 15 degrees than outdoors temperature.
Automatic control in a greenhouse
It is essential to get information on controllers and automation when learning how to build a greenhouse. The automated control is necessary to preserve a sensible environment in the greenhouse. The temperature can fluctuate significantly on a winter day what with the varying amounts of clouds and sunlight. When using a manual ventilation system, close supervision would be required. Unless and until, you are not able to monitor the greenhouse manually and carefully, both hobbyists and commercial owners should have automated systems with thermostats. It is important to install an
alarm system if a system should fail. You can use a central controller with one temperature sensor or make use of thermostats to control individual units. Keep the sensor or sensors shaded from the sun and placed them about a plant height away from the sidewalls. There should be constant airflow over them. It is recommended to have an aspirated box that has a small fan and houses each sensor. The fan moves greenhouse air through the box as well as over the sensor. The box can be painted to reflect solar heat and allow to take accurate readings of the air temperature. Keep those aspects in mind when looking for cheap greenhouse kits.