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Depending on the season, temperatures can get quite high and in turn, increase moisture in greenhouses. Water will evaporate from leaves and the soil doubling the humidity levels in the greenhouse. Every plant requires certain levels of moisture for growth healthily. This causes the need to maintain humidity in greenhouse a priority.

Before you think of increasing or reducing the moisture content in your greenhouse, first try and determine the relative humidity – the amount of moisture that air can hold at a given temperature – in your greenhouse.

Since warm air holds more moisture than cold air, condensation will occur at low temperatures when the water-holding capacity drops. At high temperatures, the risk of condensation is reduced since much of the water will remain in the vapor state.

Why is it Important to Manage Humidity in a Greenhouse?

Climate control is essential when it comes to maximizing the photosynthetic process. However, when your greenhouse becomes excessively humid, it promotes the growth of bacteria and mold that cause crops to fail. During winter, you need to reduce humidity in greenhouse structures as the condensation encourages the spread of moisture-related diseases from one plant to another.

If the conditions are left unchecked, the development of crown and root rot causes the plants to die. The moist soil also encourages the presence of pests such as gnats that feed on plant roots while the water puddles pose some health risks to the workers.

As plants transpire, they lose water in the form of vapor. In humid conditions, this water condenses on the surface and inhibits both photosynthesis and transpiration. Fortunately, you can ensure optimal transpiration by maintaining the proper relative humidity.

Optimum Humidity Level in Cold and Hot Weather

Sustainable greenhouse farming requires the proper integration of management strategies and excellent understanding of the microclimate parameters that include temperature and humidity. Naturally, humidity fluctuates since it’s affected by the prevalent weather conditions.

greenhouse inside humidity

During the summer, you need to improve humidity in greenhouse farms since your plants will lose moisture as a result of transpiration. The optimum greenhouse humidity lies between 50 to 70 percent. However, if tomato plants are grown in such conditions during the wet weather, the yields drop significantly as a result of excessive condensation.

In such cases, you might need to lower the humidity levels to 40 percent as the air will not hold the water in vapor state at low temperatures.


Why Greenhouse Humidity Drops?

Once the temperatures fall during the rainy days, the humidity drops too. In the rainy and low humidity seasons, the transpiration process is accelerated, meaning that plants will wilt and die. Managing the humidity during the wet season can be a tricky test.

Since the air feels dry and crisp, you need a humidifier to protect the plants from the threats of low humidity. Fogging the greenhouse helps to release microscopic water droplets that stay suspended in the air.


Why Greenhouse Humidity Rises?

When the temperatures rise dramatically during the sunny days, the indoor air increases its capacity to hold more moisture. Once the humidity is too high, the plants cannot lose water during transpiration or draw nutrients from the soil. If humidity rises over a prolonged period, the plant will eventually rot.

The humidity level for greenhouse structures has an impact on overall plant health. Since the plants are alive, they can be left out of breath when the summer comes with waves of heat. Space heating helps to strike the right balance between temperature and humidity since the water heater releases steam at a preset temperature according to the plants’ requirements.

Your ability to control greenhouse humidity with the ThermoPro Indoor Hygrometers will determine whether your plants will thrive or get attacked by powdery mildew and Botrytis.


How to Maintain the Humidity Inside a Greenhouse?

Greenhouse plants thrive when the temperatures vary from 21 to 30 degrees Celsius. Under such conditions, the plants photosynthesize optimally when the humidity lies within 50 percent to 70 percent. The following methods can help you to maintain the optimum humidity levels in your greenhouse.

how to maintain greenhouse humidity level

1. Monitor Greenhouse Temperature

While the ideal temperature and humidity depend on the plants that you’re growing, you don’t want the greenhouse to overheat during the summer or frost during the winter. Before you adjust the amount of moisture in the greenhouse, you need to determine the relative humidity.

Thermometers and hygrometers are must-haves if you want to succeed. A hygrometer helps to measure the humidity in your greenhouse so that you can make the necessary adjustments.

2. Increase Ventilation

Conventional greenhouses come with louvers and vents that allow excess heat to escape and cool air to enter. Polyethene greenhouses with large sheets make the installation of vents impossible.

Since they require fans to circulate the air, the monthly electrical bills rise significantly. Modern greenhouses have roll-up sides (manual and motorized) that promote ventilation by circulating the summer breezes while preventing the rain from dripping in.

3. Dehumidification

Dehumidification involves installing a heat-and-vent system to purge high humidity air and replace it with drier air from outside. The cold air that is drawn into the greenhouse is warmed to a preset temperature.

Desiccant dehumidification involves using salt to absorb excess moisture. This method reduces energy consumption by 50 percent.

4. Shade Cloths

Shade cloths help to reduce the amount of light and heat that comes into the greenhouse by acting as thermal shields. Retractable shade cloths help to protect the plants from heat stress while the shade cloths help to maintain the warmth at night when outdoor temperatures fall.

While curtains can reduce the greenhouse heating and cooling costs, they can hinder photosynthesis if misused. Programmable shade cloths can retract or extend automatically based on the indoor conditions.

Invest in ThermoPro Indoor Hygrometers

The ability to grow plants in a controlled environment is the main reason why you should invest in a greenhouse in the first place. While a greenhouse helps you to save on water and keep the pests at bay.

Since your plants will suffer on both sides of the humidity spectrum, it’s important to maintain the optimum moisture levels. The ability to determine the relative humidity with the ThermoPro Indoor Hygrometers helps you to make an informed decision on whether to increase or reduce the moisture levels.


The ability to maintain humidity in greenhouse farms can determine whether you will flap or flop. Too little or too much moisture in the greenhouse can expose your plants to the threats of pests and diseases.

For the best results, keeping the proper humidity levels in your greenhouse is vital. You need to install a space heater to help you lower the humidity during the hot seasons. Also, you need to invest in a portable humidifier to increase the humidity levels during the cold season.

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