A Beginner’s Guide to Greenhouse Fogging
Creating an effective growing climate in a greenhouse means finding the right balance between temperature and humidity. One method growers use to increase humidity and support early plant development is fogging.
Fogging creates a fine cloud of water droplets that remain suspended in the air. These droplets increase humidity and can also help cool the growing environment as they evaporate.
Why is fogging important?
Plants, like people, perform best in a comfortable environment. When conditions fall outside an optimal range, growth slows and stress increases.
Low humidity can reduce photosynthesis, limiting a plant’s ability to convert light into energy. In dry conditions, plants may close their pores to prevent moisture loss, which also restricts gas exchange. Over time, this can reduce growth and overall crop performance.
When humidity is kept within a suitable range, plants can regulate moisture more effectively. Their pores remain open, allowing efficient exchange of oxygen, carbon dioxide, and water vapour.
Fogging systems are commonly used for young plants, microgreens, and vegetative crops, which generally prefer higher humidity levels than mature plants.
How can a high-pressure fogging system help?
High-pressure fogging systems respond quickly to changes in humidity. They release microscopic droplets that are small enough to remain suspended in the air rather than settling on plant surfaces.
As the droplets evaporate, they absorb heat from the air. This can reduce greenhouse temperatures by up to 15 °C (59 °F) while increasing humidity at the same time.
When used correctly, fogging systems can support healthy plant development and reduce stress linked to overheating, wilting, and pest pressure.
Will a high-pressure fogging system fit your greenhouse?
Most fogging systems are designed to suit a wide range of greenhouse structures. Fog nozzles are typically spaced evenly above the crop to ensure uniform coverage.
Fogging is often used alongside ventilation systems. As fresh air enters through sidewall or roof vents, fogging helps stabilise humidity levels across the growing space.
How can you get the most out of a fogging system?
Fogging systems are often paired with other tools to improve control and consistency.
Misting systems
Misting systems increase humidity by spraying fine droplets over the crop. They can create consistent conditions and help prevent overheating. However, if droplet size is too large, water may settle on plants and cause damage.
Large swings in humidity and temperature can stress crops. When relative humidity drops below 30%, plant growth may slow or stop entirely.
Misting systems usually consist of pressurised tubing connected to nozzles mounted above the crop. When designed correctly, they can support germination, reduce plant stress, and encourage uniform growth.
Energy curtains
Energy curtains can also be used alongside fogging systems. By trapping humidity within the greenhouse, they help reduce moisture loss and improve overall efficiency.
What are the downsides of fogging systems?
Fogging systems require clean water and regular maintenance. Nozzles can become clogged by fine particles, minerals, or chemical residue. Sand and clay particles are particularly common causes of blockages and reduced performance.
What are the benefits of greenhouse fogging?
When matched to the right crop and environment, fogging systems can help to:
- reduce energy consumption
- provide a cost-effective way to manage humidity
- maintain conditions suitable for sensitive crops
- prevent slow growth caused by dry conditions
- reduce water use while supporting crop quality
Not all crops benefit from fogging. The suitability of a fogging system depends on plant type, growth stage, and local climate conditions.
Related greenhouse climate topics
You may also find these guides useful:
If you’re managing humidity in a greenhouse, stability matters as much as speed.
Fogging systems can change humidity levels quickly, but without reliable monitoring it’s easy to overshoot. Bluelab helps growers track environmental conditions in real time, so adjustments can be made before your greenhouse drifts outside an optimal range.
Contact Bluelab to discuss monitoring and measurement options for your grow environment.
