Temperature Control Techniques

Greenhouses offer invaluable support by extending the growing season and providing a controlled environment for cultivating a variety of crops, from specialty plants to everyday vegetables. Even in regions with short growing periods and limited sunlight, like colder climates, a greenhouse can be the key to maintaining a thriving garden year-round.

Imagine having the ability to start your plants early, shielded from the whims of unpredictable weather. With the insulation provided by materials like polycarbonate, your greenhouse can maintain a cozy atmosphere, even when temperatures drop outside. This means you can nurture your plants and keep them safe from frost during colder months, giving them a head start on growth.

But temperature control isn't just a concern in winter. As summer approaches, the challenge shifts to preventing overheating, especially in warmer climates. In places like South Africa, where the sun can beat down relentlessly, greenhouses can quickly turn into ovens if not properly managed.

So, whether you're tending to delicate seedlings or hearty vegetables, ensuring the right temperature inside your greenhouse is crucial year-round. By adjusting ventilation, providing shading, or employing other cooling methods, you can create a comfortable environment for your plants to thrive, no matter the weather outside.

Choosing the right site and position for your greenhouse is crucial for maximizing its efficiency and ensuring optimal growing conditions for your plants. Firstly, consider the orientation of the greenhouse in relation to the sun. Ideally, place the greenhouse in a location where it will receive ample sunlight throughout the day, especially during the winter months when sunlight is scarce but also an area that recieves some shade as too much sun can increase the temperatures inside the greenhouse. South-facing positions are often ideal for maximizing sun exposure. Depending what you are planning to grow you may need more shade or more light.

Moreover, consider the topography of the site. Choose a location that is level and well-drained to prevent waterlogging and ensure proper drainage. Avoid low-lying areas prone to flooding, as excess moisture can damage your plants.

By carefully selecting the site and position for your greenhouse, you can create an optimal environment for plant growth and maximize the productivity of your garden year-round.

It's crucial to manage heat buildup in your greenhouse, as excessive sunlight can lead to high temperatures that may harm your plants. The more sunlight your greenhouse receives, the more heat it will produce, necessitating adequate ventilation to maintain a comfortable climate for your plants. To monitor temperature levels, place a thermometer near the middle of your greenhouse and regularly check readings at different times of the day.

In hot climates, a simple strategy is to promote airflow by opening the greenhouse doors in the morning and keeping them open until late afternoon. This allows hot air to escape and helps prevent overheating. Other ways to reduce heat would be to install ventilation accessories/irrigation systems. 

If you reside in a particularly hot climate or have a greenhouse location that receives full sun exposure throughout the day, shadecloth can be a valuable asset. It helps mitigate the intensity of sunlight, preventing excessive heat buildup inside the greenhouse. Moreover, shading can be customized to suit different seasons and times of the year, ensuring optimal conditions for your plants.

When selecting shadecloth, ensure that it allows for proper ventilation. It's crucial that the cloth is loose over the vents to facilitate their opening and closing functions. Adequate ventilation is essential for regulating temperature and maintaining a healthy environment for your plants.

Some clients have found success by securing shade netting over the top of the greenhouse. Alternatively, you can affix it on the inside by attaching it to the greenhouse walls or roofing. This flexible approach ensures consistent shading while still allowing for ample ventilation, striking the perfect balance between temperature regulation and sunlight exposure for your plants.

Ensuring proper ventilation in your greenhouse is essential for maintaining optimal growing conditions for your plants. Installing your window vents strategically can help facilitate cross ventilation, preventing your greenhouse from overheating. Consider placing these vents to take advantage of prevailing winds, allowing for natural airflow throughout the space. 

To safeguard your vents from damage if you experience very strong winds, secure them with wire or gut attached to both sides of each vent and the greenhouse frame. Leave enough slack in the wire to allow the vent to open and close as needed. Remember to close and latch your vents securely during periods of strong winds to prevent damage.

Automatic openers on the vents can further aid in temperature control and ventilation, ensuring that your greenhouse maintains an optimal climate for your plants. To learn more about our automatic vent openers and how they work please view the product page.

Consider incorporating louver vents into your greenhouse design to enhance cross ventilation, help lower temperatures and increase airflow within your greenhouse.

Alternatively, you can opt for an extractor fan system, which offers efficient ventilation with minimal electricity consumption. To determine the appropriate fan size for your greenhouse, calculate the volume of the space (Length x Width x Average Height) and multiply by 0.75 to obtain the required ventilation rate in Cubic Meter per Minute (CFM). 

While shading and ventilation are effective strategies for preventing greenhouse overheating, the actual cooling process relies on evaporation of moisture within the greenhouse. When water evaporates, it absorbs heat from the surrounding air, acting like a sponge to cool the environment. This heat exchange occurs as energy is used to transform liquid water into a gaseous state. Efficient air circulation, facilitated by fans, enhances the evaporation process.

A well-designed misting system evenly distributes water throughout the greenhouse, promoting evaporation. The amount of moisture required depends on factors such as the level of ventilation, extent of shading, local climate, and prevailing weather conditions. For precision and reliability, consider installing an automatic misting system equipped with misting nozzles.

An affordable cooling solution involves soaking the greenhouse floor with a sprinkler hose while simultaneously opening roof vents and doors. This rapid evaporation of water helps quickly lower the temperature inside the greenhouse. Repeat this process several times during the hottest parts of the day for optimal cooling.

To prevent excessive humidity buildup, limit misting to daytime hours and use a 24-hour timer to deactivate the system two hours before sunset. In arid climates, complementing a misting system with an evaporative cooler can be highly effective. These coolers utilize water evaporation to reduce air temperature by 3 to 5°C as air is drawn through the unit and into the greenhouse, providing additional relief from the heat.

Several irrigation systems can be used in greenhouses, each offering specific advantages based on the type of crops, size of the greenhouse, and water efficiency goals. Here are some commonly used irrigation systems for greenhouses:

Drip Irrigation:

Drip irrigation delivers water directly to the base of each plant through a network of tubes and emitters. It provides precise control over water distribution, minimizing water wastage in the greenhouse.

Micro-Sprinkler Irrigation:

Micro-sprinklers are small sprinklers that spray water over a localized area. They can be mounted overhead or installed at ground level.

Fogging/Misting Systems:

Fogging or misting systems release fine water droplets into the air, creating a humid environment. This method is often used in combination with cooling systems.

Capillary Mat Systems:

Capillary mats are placed beneath plant containers, and water is drawn up to the roots through capillary action. This system is suitable for smaller potted plants.

Soaker Hoses:

Soaker hoses are porous hoses placed at the base of plants. Water seeps out slowly along the length of the hose

Overhead Sprinkler Systems:

Traditional sprinkler systems can be installed overhead to water plants. They are commonly used in larger greenhouses.

Rainwater Harvesting:

Rainwater collected from the greenhouse roof is stored and used for manual irrigation.

When selecting an irrigation system for a greenhouse, it's essential to consider factors such as the type of crops, greenhouse size, water efficiency goals, and budget constraints. Additionally, some greenhouses may use a combination of these systems to address different needs within the same facility.

Greenhouses can be heated with gas, paraffin or electricity, your heating requirements will depend on your plants, climate, location of your site, and the construction of your greenhouse.  Our greenhouses, with UV coated Polycarbonate glazing is better than most greenhouses in providing sun protection, light diffusion, and heat insulation.

Effective heating systems must maintain desired temperatures consistently, especially during both day and night. Night temperatures should ideally remain above 7°C, although certain plants may require even higher minimum temperatures. For larger greenhouses, gas heaters are often recommended due to cost efficiency, but in areas prone to power outages, electric heaters may offer more reliability. Whichever heating system you choose, ensure proper ventilation to expel any potentially harmful gases outside the greenhouse.

To determine the heating requirements for your greenhouse, calculate the required BTUs (British Thermal Units) based on several factors:

1. The total surface area of your greenhouse (excluding the floor space).
2. The minimum outside temperature for your area.
3. The maximum inside temperature needed in the greenhouse.
4. The heat loss value, typically 0.7 for twin-walled 4mm and 6mm thick polycarbonate.

Use the following formula to calculate the required BTU output for your heater:

Area x (Max temp - Min temp) x Heat loss = Minimum BTU output required for your greenhouse size.

A heating system must be able to maintain the desired temperature during the day and night.  Your inside temperature should not go below 7°C at night.  For some plants even 7°C 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:

• The area of your structure – the total square meters of the surface area (do not include the floor space).
• Minimum outside temperature-the lowest temperature for your area.
• Maximum Inside Temperature-the highest temperature you would need inside the greenhouse.
• Heat loss value:  0.7 for twin walled 4mm and 6mm thick polycarbonate.

Now the formula:

Take your Area and multiply it times the (Max temp. minus the Minimum temp).  Multiply  heat loss equals the minimum amount of BTU output your heater you will need for your size greenhouse.

Polycarbonates represent a unique category of thermoplastics renowned for their exceptional impact resistance. This characteristic has made them ubiquitous in modern manufacturing, finding applications ranging from bullet-proof glass to roofing materials for commercial structures like shopping centers. Polycarbonate's ability to withstand high temperatures also makes it a preferred material for microwave cookware, showcasing its versatility and durability. In fact, it's reported to be 50 times stronger than acrylic.

In the context of greenhouses, the walls are typically constructed using twin-walled polycarbonate panels, which are available in thicknesses of either 4mm or 6mm. This design provides added strength and insulation, creating a stable environment for plant growth while offering protection against impacts and harsh weather conditions.

Maintaining your greenhouse is essential for ensuring healthy plant growth. Regularly inspect for pests, such as bugs and fungus, and promptly address any issues to prevent infestations. Utilize natural solutions like herbs, known for their insect-repelling properties, as well as organic pesticides to combat pests effectively while minimizing environmental impact.

Keeping the greenhouse clean is crucial to prevent the buildup of debris and pathogens. Regularly hose down both the inside and outside of the greenhouse using a jet nozzle to remove dust, dirt, and potential pests. If there is buildup on the panels we recommend cleaning with a bit of sunlight liquid and a soft cloth/sponge as to not damage the UV protection on the outside of the panels. This helps maintain a hygienic environment conducive to plant growth.

By staying vigilant and implementing proper maintenance practices, you can create a thriving greenhouse ecosystem that supports the health and productivity of your plants.