Environmental Controls

Methods of controlling your greenhouse environment

A fully functioning greenhouse often has many accessories that can include watering, lighting, heating, ventilation, and various other options. The interior of the greenhouse becomes an ideal plant environment when all of the accessories work together. Proper care will cause your plants to flourish if humidity, temperature, and air circulation are controlled. Environmental Controls

Special Features of a Control System

Multiples of the same type of accessory can be grouped together or operated independently. For example, a greenhouse with two ridge vents can be programmed to open simultaneously or independently. A staged opening allows ventilation units to open at varying degrees between the fully open and fully closed positions.

The environmental controller works similarly to a residential smart house; this system automatically controls the accessories without additional effort on the owner’s part and everything operates from predetermined settings. The ridge vents and windows will automatically open when the greenhouse becomes too hot and the evaporative cooler will start to operate if a desirable temperature is not reached. The same is true for humidity and heating. Watering systems can also be automated.

A software program can be installed on your computer to control the greenhouse’s settings and daily records can be created and saved for future reference. The software can set off alarms if the temperature drops too low in winter, and can send an alert to your phone for quicker notification.

An environmental controller can provide the user with peace of mind. There should never be a concern that the greenhouse will overheat, be too dry, or vary beyond the desired temperature range. Gardeners can go to work or on vacation and come home to plants in the same condition. On the commercial side, research details can be recorded and controlled. The environmental controller will make gardening easier and more enjoyable, allowing the gardener to focus on the plants and not the mechanics.

Items an Environmental Controller Will Operate:

Environmental Controls

  • Ridge vents
  • Eave vents
  • Motorized windows
  • Heating
  • Cooling
  • Circulation fans
  • Grow lights
  • Misting systems
  • Watering systems
  • Shading systems

Ventilation

Ventilation

Operable vents, windows, and doors can promote convective air ventilation in your greenhouse. You should consider the ventilation design after the configuration is selected since proper planning can provide fresh air and cooling to the living space.

The use of ridge vents, which are placed at the roof’s highest point, reduces the chance of the greenhouse overheating.

When hot air rises and becomes trapped in the peak of the roof, the ridge vents open via a motor or a pole operator and allow the hot air to escape convectively.

Multiple bays can be joined together, and the entire roof line can open. Windows and eave vents add natural air circulation and can draw cool, fresh air into the greenhouse while forcing hot air out through ridge vents. These components assist in circulation and temperature balancing within the greenhouse.

Thermostatically Controlled

Environmental Controls

Ridge vents and windows can be mechanically controlled by a linear actuator motor. This motor is specifically designed for high humidity areas such as a greenhouse.

All controls are contained in weatherproof housing. Each vent operates based on temperature, which is read on a thermostat mounted in the greenhouse.

A signal is sent to the motor, which opens the vents when the thermostat reaches a designated degree. Correct thermostat placement is necessary to prevent false readings from direct sunlight or heaters.

Thermostats are set to operate based on a temperature range of approximately 5 to 10 degrees. For example, vents can be set to open when the greenhouse reaches 70 degrees and close when the temperature drops to 60 degrees; the vents will remain open and allow air to circulate while the temperature is within this range. The vents can also be forced to open manually if needed, but are intended to provide effortless natural ventilation to the plants and people inhabiting your space. Ventilation

Heating and Cooling

Fan

Fan Options

Plant health is vital to a greenhouse’s success. Air circulation plays a major role since air movement reduces plant disease and can stimulate fertilization.

  • Circulation fans constantly move air within a greenhouse and are essential to the plant’s health. The fans also eliminate hot and cold pockets while keeping temperature and humidity uniform. Placing fans in opposite corners of the greenhouse helps keep a consistent rhythm of air movement and also reduce condensation.

  • Intake louvers and exhaust fans are typically used with non-insulated greenhouses. The exhaust fan expels excess heat from the greenhouse, while the intake louver brings in fresh air—together they regulate temperature and promote healthy plant growth.

Heating and Cooling

Heating and Cooling

The interior temperature of your greenhouse is critical to how well your plants will grow. Most greenhouses will need to be heated and cooled to provide the proper indoor environment for plants.

Solar Heat Gain

All glass structures are prone to solar heat gain and the greenhouse effect.

Heating

Heating

Any heat source will keep a greenhouse warm, including electric, propane, natural gas, oil, radiant, wood, or solar thermal. However, some tropical plants require the greenhouse be kept at a constantly warm temperature, while hardy cold crops—like lettuce and kale—will thrive at lower temperatures. Different heating systems have different advantages and greenhouse sizes and shapes will determine if one heater or multiple heaters will be required.

Cooling

Cooling

Cooling a greenhouse is more involved and specific than heating. Most forms of heating will provide the same result, but the wrong type of cooling can prove detrimental to plants. An evaporative cooler is needed when this venting is not sufficient. This system blows outside air over a wet pad that takes the heat out of the air and cools it. This cooler air is then introduced into the greenhouse. This method is reliable, efficient, and can be automatically controlled.

Lighting and Shading

The number of hours a plant grows can be extended with supplemental lighting known as grow lights. Most year-round greenhouses require extra lighting during the winter months to ensure plants receive the necessary photoperiod for normal development. Grow lights can be used to produce artificial sunlight on shady days when plants do not receive sufficient sunlight. Plants can produce more flowers and fruit in a shorter amount of time with this additional light.

Plant Lighting

High Pressure Sodium Lights

High Pressure Sodium Lights

A high-pressure sodium lamp emits more light in the red/orange wavelengths to promote more flowers and fruit and is recommended for production of vegetables and cut flowers. Using this light constantly, even during daylight, can provide increased production.

Metal Halide

Metal Halida

A Metal Halide grow light produces more light in the blue wavelength spectrum to promote more of the vegetative growth.

Plants grown under this type of light are typically taller and bushier.

Functional Work Space Lighting

Functional Work Space Lighting

There is less time for gardeners to work with their plants during daylight hours in the winter. Unfortunately, most lights are not designed to withstand the amount of water and humidity found in greenhouses. Lights will eventually rust, break, or stop functioning. A water-resistant, greenhouse lighting system with fluorescent lights that can be mounted at the ridge of your structure for task lighting.

Shading

Summer sun may be too intense for plants to grow. One way to avoid plants from burning or dying is to install a shading system. Operable, fixed, interior, and exterior shading systems are available.

Interior Fixed

Interior Fixed

An interior fixed shade system permanently attaches to the frame and is appropriate for greenhouses with plants such as delicate orchids or tropical flowers.

Exterior Fixed

Exterior Fixed

These fixed shades systems will prevent heat and light from entering the greenhouse, stay in place, and do not move. These shades are recommended for locations with intense sunlight year-round.

Interior Operable

Interior Operable

An interior operable shade system provides control over the amount of light entering the greenhouse. Shades are available in manual or motorized options and can be drawn on bright days or retracted on overcast days.

Exterior Operable

Exterior Operable

An exterior operable system consists of shades mounted on the outside of a greenhouse. The shades reduce light and heat buildup in the greenhouse, which helps promote healthy plants. Manual and motorized options are available, along with various shade fabric colors.

Exterior Mounted

Exterior Mounted

The shades on this system are raised 5 to 7 inches above the ridge and allow for air circulation, which reduces the temperature of the glass.

Irrigation

Water is an essential element for plants in a greenhouse and needs to be carefully controlled. An automatic watering system can regulate the flow of water and nutrients to your plants without you being onsite. There are various system choices available for your selection.

Misting Systems Drip Systems

Misting Systems Drip Systems

  • Suspended: System is suspended from the rafters and does not require bench space.
  • Polyrail: A rail is attached to the bench which disperses water through a nozzle.
  • Risers: Individual risers are attached to the bench top. Each riser can be moved to accommodate plant rotation.

Drip Systems

Drip Systems

A drip system acts somewhat like a soaker hose. A black hose with attached individual drip tubes spans the length of the bench.

Each drip tube is placed into a flower pot. The tubes then supply continuous drops of water into the containers.

Each plant receives the same amount of water. Different pressure rates, or drip rates, are available, and zinc tips keep the tubes secured in the pots.

Fogging

Fogging

Tropical plants often need 60 to 80 percent humidity, which is difficult to achieve without a fogging system.

A fogger produces humidity required to successfully grow your plants without disrupting visibility.

The fan blows water into the greenhouse, produces humidity, and creates a slight fog.

Hose Reel

Hose Reel

Hoses normally take up valuable floor space in a greenhouse and are difficult to manage. A reel can be mounted to a wall and pivots left and right. Simply tug the hose, and it automatically retracts into the holder, clearing floor space. The unit can be mounted on the exterior or interior of the greenhouses.

Greenhouse Water Features

Water and plants go hand-in-hand. Incorporating a water feature into a greenhouse can not only provide character, but will also have both a practical and decorative use. Water fountains and bird baths are often used with outdoor landscaping, but they can also be incorporated into a greenhouse. Through the addition of a water feature, you can bring the relaxing sound of water into your greenhouse.

Ponds are another water feature commonly found in greenhouses. The pond can be an additional medium for growing aquatic plants, such as water lilies, water hyacinths, cannas, and elephant ears. Waterfalls can be designed in conjunction with the pond where you can also raise fish, which will help to fertilize the plants growing in the water. The water environment will allow you to grow year-round and enjoy an outdoor environment

Resources

Greenhouse Location Recommendations
Greenhouse Planning Worksheet
Greenhouse Accessories

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