Location of where the greenhouse is to be built should be the first consideration. The best choice is the south or southeast side or a building to get the greatest possible degree of sunlight. All day sun is best. An east side location is most effective if the greenhouse is going to be used from November to February. A north structure is only good for plants that require little light.
Good drainage is essential so rainwater and irrigation water will drain away. Consideration of light needed for the plant, locations of heat, water and electricity is also necessary. There should be good shelter from winter winds. The greenhouse should be convenient for both people and utilities.
When deciding on the structure plan for bench space, storage and room for expansion. Large greenhouses are easier to manage because they hold their temperature better than a smaller construction. The minimum size of the greenhouse should be six feet wide by twelve feet long for a freestanding greenhouse.
The frame should be built of wood, galvanized steel or aluminum. Plastic pipe is a poor choice as it does not meet snow and wind load requirements. Covering of the frame may be glass, fiberglass, a rigid plastic or plastic film. Each material has both advances and disadvantages so they should be considered carefully.
A frame can be built in several different styles. Some of the common ones are the quonset, gothic. rigid-frame, post and rafter and A-frame.
Traditionally glass is used as covering. It looks good, is inexpensive and has the property of being able to exist for an indefinite duration. It is available in many forms making it suitable for almost any style of greenhouse. The disadvantages are that it is easily broken and expensive to build. Good foundation is required and the frame must be strong and fit well together. A good grade of fiberglass that is clear or translucent can last up to 20 year but the coating will eventually wear off making it necessary to recoat it with resin.
The floor of the greenhouse should be covered with several inches of gravel to aid in the drainage of excess water. A walkway made of concrete or gravel will make for easy access to the plants. Gravel aid to produce humidity when sprayed with water.
The sun provides solar energy and some heat, but a system to regulate the environment in the greenhouse must be provided by using heaters, thermostats and other equipment. As much as twenty five percent of the daily heat will come from the sun but the greenhouse may need a greater source of heat especially during the winter months. A 220-volt circuit electric heater is clean, effective, and work well. A less expensive option would be to use a wood stove that is properly vented to the outside. Refrain from using a kerosene heater as the gases have a negative effect on some plants.
Shades that roll up can be made from wood, aluminum, netting or paint. It is essential to shade plants when the light saturation may be high as in the hottest months of summer.
An automated system with a thermostat is best as it controls the environment within the greenhouse.
Watering is best if done by an automated watering system. Hand watering is not always possible for different reasons and an automatic watering system will help to assure the plants get the right amount of water each day. Time clocks can be used to control the water
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