TIPS ON KEEPING YOUR PLANTS AND GREENHOUSE FIT FOR ALL SEASONS
Hobby greenhouses are used largely in winter months to keep plants warm and in the spring and fall months to grow seedlings for both flowering plants and vegetables. In some northern parts of the country, due to a very short growing season, the only way to have a vegetable garden is to grow one in a greenhouse. In winter, temperatures at night in the greenhouse cannot go any lower than 45 degrees or less depending on your plants. The trick is how to maintain the right temperature for your greenhouse in winter and summer.
In the summer months, the greenhouse must be kept cool-under 85 degrees, if you want your plants to survive. There are a number of ways to maintain the right temperature for your plants. Below are listed some tips and accessories that we strongly recommend to assure that your plants will be comfortable no matter how extreme temperatures are in winter and summer.
1) Greenhouse Shading
The shade cloth is probably the most important accessory you will need for your greenhouse, in particular, if you live in a very hot climate. The shading will shield it and your plants from excess sun between 9 a.m. and 5 p.m. or even until 7 p.m., if your greenhouse has extreme western exposure. The RION shade cloth is of the highest quality and is used for any number of different types of plants. The cloth prevents irradiation damage to your plants, reduces the heat in the greenhouse in summer and adds insulation during the cold weather. Whatever type of shade cloth you choose, make sure the cloth is big enough to allow your vents to open as proper ventilation is another import key to maintaining the correct temperature for your plants.
2) Greenhouse Ventilation
Please be sure and purchase extra window vents with your greenhouse. Cross ventilation will also prevent the greenhouse from overheating. Place the vents so that they will take advantage of prevailing winds. Most 8 x 12 greenhouses should have vents that equal in size to 15% of the floor plan. The roof vent should open 45 degrees above the top of the greenhouse. To make sure that your vents do not blow away attach a wire or heavy-duty string to both sides of each vent and the greenhouse frame. Allow enough play in the wire or string to allow the vent to open and close as needed. In strong winds, be sure to close your vents and latch them securely.
RION offers two types of vents, one that is manually operated and one that comes with an automatic opener. We recommend the automatic opener which can be attached to all vents. The opener will automatically open and close the vents based on the temperature inside the greenhouse.
An alternative to extra vents is having a thermostatically controlled exhaust fan system. Using very little electricity, the adjustable thermostat automatically provides ventilation for your greenhouse.
The proper size fan will change the air intake in about 1.5 to 2 minutes. To select the size for your greenhouse, determine the volume of the unit (Length x Width x Average Height) and multiply by 0.75 to obtain the ventilation rate in Cubic Feet per Minute (CFM). For the exhaust fan to operate effectively, fresh air intake shutters must be provided at the opposite end of the greenhouse. The shutters open with the flow of air drawn into the greenhouse by the fan or they can be opened and closed by a motor.
3) Greenhouse Misting
Although shading and ventilation will keep your greenhouse from seriously overheating, The actual cooling of a greenhouse comes from the evaporation or moisture inside the greenhouse. The evaporating water soaks up heat like a sponge, when heat is used to change water from a liquid to a gas. Good air circulation from fans increases evaporation.
A good misting system disperses water evenly around the greenhouse. The amount of moisture needed depends on the amount of ventilation, shading provided, your climate and the weather. One common system is to soak the floor with a sprinkler hose. The most accurate and most reliable is an automatic system of misting nozzles.
Only apply misting during the day to avoid excess humidity at night. Use a 24-hour timer to shut off the system 2 hours before the sun goes down. If you live in a dry climate, in addition to your misting system an evaporative cooler works well. Air is cooled 10 to 20 degrees by water evaporation as it is drawn through the cooler and into the greenhouse.
4) Heating
Greenhouses can be heated with propane or electric heaters with thermostatic controls. Your BTU heating requirements will depend on your plants, climate, location of your site, and the construction of your greenhouse. Your RION greenhouse with its UV coated Polycarbonate glazing is better than most greenhouses in providing sun protection, light diffusion, and heat insulation.
The most popular heating systems use either electricity or gas. A heating system must be able to maintain the desired temperature during the day and night. Your inside temperature should not go below 45 degrees at night. For some plants even 45 degrees is too low. For larger greenhouses, gas heaters are recommended because it is less expensive. However, if your area suffers power outages, a gas heater might be more reliable. Any type of heating system you use should be properly vented to the outside of the greenhouse to avoid build up of any harmful gases.
To calculate how many BTUs your heater will need to provide and maintain the correct temperature for your greenhouse you will need to know:
RION: GH44 - 295' GH46 - 384' GH48 - 483'
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Minimum outside temperature-the lowest temperature for your area.
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Maximum Inside Temperature-the highest temperature you would need inside the greenhouse.
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Heat loss value-for a RION greenhouse it is .70
Now the formula: take your Area and multiply it times the (Max temp. minus the Minimum temp)
Times heat loss equals the minimum amount of BTU output your heater you will need for your size greenhouse
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