How climate impacts your greenhouse’s costs and production

It’s a common misconception that greenhouses are “magic boxes” that produce a perfect internal environment no matter the external climate conditions. 

Theoretically, it’s possible to have a lush rainforest greenhouse in Antarctica, but practically you would need the GDP of a small country to build the greenhouse and keep it running at optimal temperatures despite the harsh exterior conditions. 

As much as we’d like to, we don’t live in a theoretical world where greenhouses are "magic boxes" that overcome any environmental challenges. Unless you have an unlimited budget, that is. Instead, they’re a tool to enhance a reasonable climate to achieve optimal results for your crops.

Now let’s dive into some important aspects of climate control, emphasising temperature and airflow for optimal growing conditions. Understanding and then manipulating the climate in your greenhouse is the road towards maximising yield, minimising overheads, and growing sustainability.

Deciding your greenhouse’s location

A greenhouse’s location is not just about the available space or convenience. It's a strategic decision that hinges on the local climate. 

Sunlight is crucial for plant growth, but the intensity and duration need to be just right to avoid the need for excessive shading or artificial lighting. Temperature extremes also play a significant role. In colder areas, heating costs can skyrocket, while cooling systems become essential in hotter regions. Reliable water access is also vital. And local humidity levels can impact plant health, too. High humidity fosters mould and disease, and low humidity requires more frequent watering or humidification. 

In countries like South Africa, where climates range from Mediterranean to subtropical and semi-desert, selecting a location requires a detailed understanding of microclimates. Such diversity means that greenhouses may need to adapt to fluctuating temperatures and varying humidity levels throughout the year, making the decision even more complex.

Hot or cold?

Temperature management in greenhouses varies significantly between hot and cold climates.

Colder climates

Heating a greenhouse is relatively straightforward. By raising the temperature, we can also control humidity levels, as introducing fresh air is less necessary. This control comes with a cost, but it's often justified in regions where transporting heavier crops is logistically challenging and expensive.

Warmer climates

The economics shift. Cooling and dehumidifying a greenhouse in a hot climate is a costly affair. That’s why it’s more economically viable to grow crops in warmer climates during winter months, rather than investing in high-tech, expensive cooling systems.

Understanding airflow dynamics

The movement of air is a fundamental aspect of any greenhouse. It's about striking the right balance – ensuring adequate airflow for plant transpiration without overdoing it. 

Think of it as the greenhouse equivalent of human sweating; too little and the plant overheats, too much and it dries out. There are two primary approaches to managing air flow in greenhouses:

Naturally ventilated systems

This setup utilises the principle of thermal buoyancy and wind to facilitate air movement, similar to a natural breeze. Greenhouses using this system often feature adjustable roof vents and side vents, allowing growers to adjust air exchange based on external weather conditions. The key advantage of natural ventilation is its energy efficiency, as it reduces the need for mechanical systems. However, the effectiveness of natural ventilation is highly dependent on external factors like wind speed and direction, temperature, and greenhouse orientation. This can lead to challenges in maintaining consistent environmental conditions in the greenhouse, like excessive CO2 levels, and especially in terms of humidity and temperature control.

Closed ventilation systems

Closed ventilation systems rely on mechanics to regulate the greenhouse environment. They typically include fans, air circulation systems, and sometimes air conditioning units to maintain optimal conditions for plant growth. These systems allow for precise control over temperature, humidity, and CO2 levels, independent of external weather conditions. This is particularly beneficial in hot climates, where excessive temperatures can be detrimental to plant health. As closed systems are more isolated from the outside, they also reduce the entry of pests and diseases. However, this method is more energy-intensive and comes with higher operational costs due to the need for continuous power supply and maintenance.

The Bottom Line: Climate is key

Climate is our biggest consideration when designing and building a greenhouse. Not only does it determine the initial greenhouse setup costs but also the ongoing operational expenses and ultimately, the profitability of your venture.

Remember, a greenhouse enhances your local climate; it doesn't replace it. Choose your location wisely, understand the climate you're working with, and let us help you turn a good climate into a perfect one for year-round, efficient, and profitable farming.

At Vegtech Netafim, we are committed to sustainable and innovative agricultural solutions. Through precision farming and a deep understanding of the intricacies of greenhouse climates, we strive to empower farmers across Africa and beyond. For assistance, give us a call at +27 21 987 6980 or drop an email to info@vegtech.co.za