During tomato production in modern glass greenhouses, high temperatures can be a serious problem during the summer months. If the temperature between the plants is higher than 32-35 ° C, then there can be problems with fruit formation and also with minerals absorption and pollination. For this reason certain activities and measures are taken in order to cool down and control the temperatures in the greenhouse, at least between the plants.

Here are some methods to cool down and control the temperature in the greenhouse:

Greenhouse structure height

The higher the greenhouse, the larger will be the volume of air above the plants. Also more Sun energy will be needed in order to increase the temperature of the air for one degree. So the higher the greenhouse, the cooler it will be inside. Five meter post height (16.4 feet) used to be the standard. Nowadays it’s a bare minimum. More and more growers are building a 6m (19.6 feet) post height, 7m (23 feet) post height or even 9m (29.5 feet) posthight greenhouses.

Air circulation

Plants are cooling themselves by the process of transpiration, water evaporation from the leaves. By using ventilators in the greenhouse, we are promoting air circulation and making plants cooler.

Activating horizontal shading screen

This can drop down a temperature a little. Some growers are activating their energy screens to up to 80 %, leaving a 20% gap for air circulation. High percentage shading screens of 60-70 % shade are not recommended because they block the light and drop down the tomato production, and can be used only in a short period of extreme heat.

Roof cooling

Roof cooling is another way to drop down a greenhouse air temperature for few degrees. It is done by positioning a water sprinklers on the top of the greenhouse, at the roof ridges, and spraying the water. Water is evaporating on the glass surface, cooling the glass, and colder glass is cooling the greenhouse air. The higher the greenhouse, the lower is the effect of this system.

Mist installation – high pressure system

This system is costly, requires special water and can drop down a temperature for several degrees. But the drawback is that it works only in very dry climates, and it is increasing humidity in the growing area which is something that we do not especially want, especially with tomato plants. So with tomato growers this system is not so popular.

Low pressure systems for growing tomatoes should be avoided because there is a chance of water droplets reaching the tomato plants which is not good for production and plant health in general.

Pad and Fan system.

This system is very popular and recommended in the desert and very warm areas. It requires low humidity air. And can be very effective. Greenhouses need to be designed in a special way for this system to function properly. Effective range is from 35 to 45 m (115 – 148 feet) and can drop down greenhouse temperature for 20 °C (36 °F) or more.

Active cooling systems.

These are classical air conditioning systems or in some cases heat pump systems. Anyhow, they are very expensive and they use a lot of electricity. Equipment suppliers have a saying it takes more energy to cool down air than to heat it up. So this system should be avoided by all means. And it can be used only in special cases, in small greenhouses or where there is a very expensive product or service done.

There are few more specialized cooling systems patented by the owner companies. But these are rare cases, not seen so often within the general greenhouse owners.

Look for the upcoming post where this special system will be covered.