Greenhouse Fogging Systems: How to Control Your Glasshouse Environment

Greenhouse fogging systems are designed to control the environment inside of your glasshouse. It’s a technology that’s been in use since the 1980s, but which is emerging from its problems of the past.

Before computers, growers had mixed opinions about their efficacy. This was due largely to the fact that there were many things that occurred inside of their glasshouses over which they felt they had little control.

Nowadays, software has alleviated these concerns. It enables a more efficient circulation of air from outside to inside and from inside to outside, for example, and filters now make it much less likely that nozzles will get clogged with the minerals that are dissolved in the hard water of the UK.


Purpose of greenhouse fogging systems

The purpose of greenhouse fogging systems is to maintain optimum growing conditions within your glasshouse by controlling temperature and humidity. Doing so removes water stress on plants.


Water stress occurs when plants experience drought-like conditions such that either the supply of water to the roots is limited or moisture evaporates from their leaves faster than they can replace it.

Plants do adapt in order to survive but, even the earliest stages of doing so, it’s enough to make plants unsalable.

In order to sustain life, plants will shed their flowers first and the buds will fail to mature and open. Then the leaves will fall off and, if left for long enough, dormancy will follow.

When plants are getting the right balance of water, temperature, and humidity, they are healthier and have better yields.


Leaf health is essential, too, because plants absorb CO2 and moisture through them. Not only do yield increase, but the potential for healthy plants also improves. Germination is must faster, and the potential for disease is greatly reduced.

In fact, using greenhouse fogging systems is probably the most effective way to control humidity your glasshouse.



In order to control humidity, the mist must be fine enough to evaporate into the air without making the plants wet. To do this, the delivery system has to create “droplets” that are no more than 10-20 microns in diameter – roughly half the width of a human hair.


Such rapid absorption, known as flash absorption also prevents condensation. This is essential for consistent light levels in your glasshouse and avoids water dropping onto your plants from the ceiling.


Greenhouse fogging systems have another use, and that is to reduce temperature.

In hot and humid climates, refrigerated air conditioners are used to remove the warm moisture so that temperatures will fall; but in hot, dry climates, evaporative coolers add it to the air instead. This system works because water retains its temperature, whatever it is, for longer even when the air is much warmer.


It has been suggested that to make this work in your glasshouse, you should keep the humidity a little low so that when moisture is added, the temperature will fall faster. If the humidity is already high in a warm glasshouse, then the water vapour in it will also be high; and adding more moisture, even if it’s cooler probably won’t make much difference.


How greenhouse fogging systems work

A properly designed system will distribute the moisture into the air evenly. This will ensure uniform growth among your plants.

In most cases, a high pressure pump is used to send water through pipes, and then special, anti-drip nozzles propel a fine mist into the glasshouse.

Sometimes the “fog” is sprayed via powerful misting fans.


Other benefits

Such systems aren’t limited to increasing humidity or lowering temperature. Insecticides, fungicides, and nutrients can also be added to the mist.

The need for irrigation is less, too.



It’s worth noting that greenhouse fogging systems don’t necessarily work everywhere and in all circumstances.

Generally speaking, they work best when the interior temperature is at its peak in any given day. That’s because that's also the time when the air will be the driest.


Some seasons are better than others, too. Summer is an obvious choice, but it can also be effective in winter when artificial heat is used to keep temperatures up.

What do you think?