Managing the humidity levels in your greenhouse can be challenging. If you’re worried about the high or low humidity levels in your greenhouse, you’re at the right place to start finding a solution for a cleaner and safer greenhouse.
How to control and manage humidity levels in a greenhouse:
| General Humidity Management | Adjusting High Humidity Levels | Adjusting Low Humidity Levels |
|---|---|---|
| Proper watering | Warming plants | Spraying water |
| Adequate spacing | Ensure proper air circulation | Drip irrigation systems |
| Removal of weeds | Correct ventilation | Shades and shade nets |
| Squeegees/Well-drained floors | ||
| Anti-drip plastics | ||
| Proper glaze selection | ||
| Greenhouse pitch |
Depending on the season, there will be various fluctuations of humidity levels in your greenhouse that can eventually become harmful, causing diseases and bugs in your soil and crevices of your greenhouse. Read on to learn how to control the humidity levels in your greenhouse and other tips that will help your greenhouse flourish.
How to Control Humidity Levels in a Greenhouse
Humidity levels can have drastic effects on your plants when uncontrolled or forgotten. Both ends of the spectrum can have harmful effects.
High moisture is harmful because it brings pathogens and diseases. The moisture promotes germination of fungal pathogens and powdery mildew, which can be harmful to your plants and also for you. Fungal molds are dangerous and need to be prevented and removed. Diseases can quickly spread from plant to plant by splashing debris.
Many common sources of humidity and moisture dysfunction come from:
- Dripping water from the condensation covering the greenhouse
- Dripping water from glazing
- Dripping water that falls onto plant surfaces
- Puddles of water in corners and behind shelves
Furthermore, if you remove all the humidity and lower your humidity level, this will also lead to negative implications for your plants. When the humidity is too low, your plants may die from heat or thirst, depending on the species.
General Humidity Management
The following general humidity management options involve merely controlling the humidity level to provide ways of managing humidity levels in the greenhouse and methods on how to adjust high or low humidity levels, respectively.
Regular and Proper Watering
Whether your humidity is too low or high, always practice regular watering. In general, keep these three things in mind to avoid unwanted humidity from watering:
- Prevent excess watering
- Avoid puddles
- Water early in the day
Proper watering benefits plants, and adding just enough water prevents excess water from falling on the floor and forming puddles. Be careful not to leave large puddles of water in corners and areas that do not get direct sun.
In warmer weather, watering early in the day is an easy trick to decrease unwanted humidity. If there are water droplets or water puddles, they will dry throughout the day, which will result in fewer bugs to search for nooks at night and help prevent fungi from forming.
Adequate Spacing
Thick canopies are natural and a healthy feature of plants, but it is a culprit in locking down moist and humid air into the night. Mesh benches and proper spacing will help keep air circulating under plant canopies and let the transpired air to move out to the open and not stay trapped under the thick canopies.
To avoid canopies from trapping moisture:
- Space out plants
- Keep canopies dry
- Keep canopies ventilated
- Don’t overlap canopies
Remove Weeds
Remove your weeds! Although often overlooked, weeds are also a culprit to adding humidity into the air. Weeds hold moisture in the leaf, then transfer it to the canopy and generate moisture through transpiration.
Squeegees
This is a trick that many homeowners use for preventing mold in showers. Thankfully, this works well in any circumstances where you need to remove water from hard surfaces.
A squeegee can remove more than 50% of the water from your greenhouse surface, especially in areas you see excessive condensation. Just run a squeegee and direct the runoffs to the drains!
Well-Drained Floors
Speaking of runoffs, this leads us to our next suggestion: drain your floors thoroughly. To avoid puddles throughout your greenhouse, be sure to have well-draining floors and drainage pathways.
This implies that you need to ensure that the water (from watering, plants, and leaks) has a flow path to follow to the drain. It’s easy to use elevation tricks or install drainage tile mats to handle runoff.
Anti-Drip Plastic
If you continuously find a stream of condensation on your glazing, try using anti-drip wetting agents on the hard surfaces. Anti-drip agents come in forms of sprays or, often, in the formulation of the glazing for greenhouses.
Select the Right Type of Glazing
When possible, use double glazing for your greenhouse rather than single glazing. Double glazing provides better insulation for temperature control and unwanted condensation.
Double glazing also provides better temperature control inside the greenhouse via the glazing surface. When the glazing surface is warmer, the dew point will be harder to reach than single glazing, which will fall short in preventing the temperature drop.
Greenhouse Pitch
A greenhouse with a steep roof can also guide water droplets to follow the path along with the glazing rather than drop onto the plants below. A recommended roof pitch is 6:12, which will allow the droplets to run off on the surface.
Adjusting High Humidity Levels
When you have high humidity levels, as mentioned previously, you will run into several unwanted problems. These are issues that generally arise at any time of the year, and, depending on your conditions, can be critical to your plants’ health and requires immediate adjustment.
Keep in mind that moist places caused by leaky pipes and drippy corners attract unwanted pests such as cockroaches! Even the cleanest greenhouses are prone to terrible pests if the moisture level is too high.
Warming up the Plants
During spring and winter, most condensation happens at colder leaf surfaces and the air around it. By introducing heat from the bottom, you can improve the air with natural circulation.
Most people know that “hot air rises.” This method of using hot air is a simple contribution to the air circulation method. A heated air introduced from the bottom carries out the trapped moisture under canopies out to the open, which can then be carried out with proper circulation and ventilation.
Additionally, it warms up the plant leaves and surfaces that tend to be cooler than the surrounding air, which decreases its chances of condensation!
Air Circulation
Along with ventilation, air circulation, in general, will prevent the moisture from sitting on plant leaves as temperatures drop below the dew point. Thankfully, many hot air furnaces come with fans. This is to be used carefully in the winter as excess ventilation and circulation could also be harmful to your plants.
Ventilation
Ventilation is a critical factor in releasing some of the moist air outside of the greenhouse. Ventilation and proper heating methods can significantly help in reducing moisture levels in a greenhouse.
Heating and ventilation can work in conjunction. For example, with increased air movement, heat can be used to carry the densely moist air in the open-air direction.
Adjusting Low Humidity Levels
For some plants in the summer, the hot pressure can make them suffer. With the help of moisture and humidity, they can experience a dampening down process, which helps them from overheating. Some heat-sensitive plants are tomatoes and cucumbers.
Spraying Water
Just like the opposite of extracting moisture from the air, the simple alternative is spraying water to the surfaces of the greenhouse.
By introducing water to the greenhouse’s flat surfaces in the early morning, the water on these surfaces will evaporate throughout the day and bring in moisture as it leaves with the heat. This provides a slow humidity addition for the air around the plants.
Drip Irrigation
For plants or conditions that require extra water and moisture, use drip irrigation systems or fine spray systems to deliver moisture directly to plants when they need a little pick-me-up. For a hands-free method, you may want to connect your humidity level indicator, such as a hygrometer like the one found on Amazon, to spray water in automated controls.
Shades and Shade Nets
Additionally, to prevent direct heat on such plants, you can add shades or meshes to the greenhouse walls and ceilings to prevent rapid evaporation and redirect and dampen the sunlight.
Shade or Sun cloths, like this type found on Amazon, come in various shading rates, are budget-friendly, and are highly effective against harsh sunlight. This will be a great addition to not only control humidity but also to control sun exposure for the more delicate plants.
Understanding Humidity Levels in your Greenhouse
Although it may feel overwhelming, don’t worry! By growing your plants in a greenhouse, you have the benefit of controlling your plants’ environment. With proper tools and an understanding of humidity, temperature, and light, you’ll be able to provide a suitable home for your plants to grow in.
Whether it’s during low or high humidity, always practice good housekeeping and regular gardening practices. Regulating humidity levels can root from just the basics of keeping the greenhouse floors dry, no pun intended.
Water puddles on the floor, leaves, the soil, or growing media can cause evaporation and increase the relative humidity, leading to condensation and a moist and humid environment. Additionally, evaporation adds humidity to the environment around the plants and takes away the energy needed to keep the greenhouse warm.
Relative Humidity
RH stands for Relative Humidity. The moisture in the air is often expressed by the relative humidity. This is a ratio of the weight of moisture present in the air and the total moisture holding capacity in that unit of air (at a specific temperature and pressure).
Humidity has an essential connection with temperature. If you think about how much hotter a hot sticky summer day is, you can relate.
What about Temperature?
Temperature plays a significant role in the ratio of moisture for RH. The warmer the air is on the temperature scale, the higher the moisture capacity it will have. Therefore, warm air has a higher moisture-holding capacity than cold air.
- Higher temperature = More moisture the air can hold
- Lower temperature = less moisture the air can hold
So, when the temperature rises inside a greenhouse, the RH will decrease, even though the same amount of moisture is held in the air.
To give you a better perspective: every 20 degrees Fahrenheit increase in a greenhouse, the RH decreases by one-half. This means that the 20 degrees increase doubles the moisture-holding capacity of the air. The air in a warm 80 degrees Fahrenheit greenhouse can hold double the amount of moisture compared to a cool 60 degrees Fahrenheit greenhouse.
So, cooler air has less capacity to hold the water droplets, which is what can be harmful to your plants in the already humid air.
What is Dewpoint?
This comes down to the dew point. Dew point, defined by