There are special conditions underneath glass covers: heat, high humidity levels and sensitive seedlings. Become an expert at gardening with our tips for ventilation!
Estimated reading time: 11 min
Even the most ambitious hobby gardener cannot be present every single day to balance out the climate inside the greenhouse and regulate temperatures by ventilating manually. Too much humidity leads to mould growth and damage on the plants. Inventive gardeners come up with many creative ways to ventilate their (windowless) greenhouse: There have been incidents where fans were taken from PCs and used in the garden! A little while ago, one of our customers pointed out how hard it is to find a suitable fan for gardens and particularly greenhouses. But there are so many efficient devices, even with automatic humidity control.
In this blog post we will show you economic ways to achieve ideal temperature and humidity levels for your plant breeding.
- Sufficient air movement / airflow
- Supply with fresh air
- Adjustable temperature balance
- Automatic control of humidity
- Low power consumption
- Easy cleaning
- Simple mounting options
- Trouble-free operation despite high temperatures of about 50°C
- Resistance to humidity and weather
- Damage due to damp on plants and building materials
- Mould and blight
- Damage to growth due to pent-up heat
- Big temperature differences (day / night)
- Insufficient pollination (with wind pollinators)
Typical problems when growing plants under ceilings
What a joy when seeds show first signs of saplings. Yet those delicate seedlings require a good, stable climate to continue growing. The growth of mould spores in the warm humid atmosphere must be prevented at all costs, the seedlings are still quite vulnerable to temperature fluctuation, bacteria and spores. The very hot, suffocating heat must be moved and, if required, exchanged in regular intervals.Just like modern buildings with heat storage, sophisticated greenhouses also have an airtight building envelope. This makes a controlled air supply and extraction a necessity, that also transports condensation water. This prevents mould growth (beginning at 60% humidity).
Our tips guarantee a good harvest
In the best case, temperature, oxygen and water vapour contents of the air are coordinated with the growth phases of the plants. Heat and humidity in particular should be controlled to ensure ideal conditions. If the temperatures increase too much, seedlings quickly collaps and lose their strength.
Tip: Please note that each kind of plant has its very own preference when it comes to temperatures, so try to select your seedlings accordingly. This makes caring for them much easier. Most plants prefer a daytime temperature of 20-30°C.
Are there different kinds of ventilation?
- Manual ventilation (window/door)
- Automatic window ventilation without electricity and batteries
- Simple supply and exhaust ventilation with fans
- Fully automatic ventilation depending on humidity or temperture
Possibilities and limitations of window ventilation
Recommended airflow for a greenhouse with 25 m2 = 150-160 m3/h
Generally speaking windows as a means of ventilation should make up about 10-20 percent of the surface area in the greenhouse. However not every house has enough outlets that ensure sufficient airflow when arranged correctly. In order to use the stack-effect, windows and the roof and the sides are positioned on opposite sides in different heights. The right location (sunny or shady side) and size of the outlets can further prevent unfavourable temperature and pressure levels.
It is not always possible to add furter side windows and skylights to the foundation work later on. This simple measure is often not enough during summer when temperatures rise to unbearable levels, as it does not guarantee sufficient air movement and air exchange. Furthermore the windows need to be opened and closed manually which is often impossible to in a timely manner.
Automatic window ventilation without electricity and batteries
Basic technology relieves gardeners from the duty of manually opening windows: Hydraulically operated roof or window fans require not external power supply. Instead they move a poppet that lifts the window once wax components in the cylinder react to temperatures. As soon as the outdoor temperature decreases again, the window is closed automatically by the same technology. Installing this type of window opening is easy, however the bendable materials are susceptible to high wind.
Plantation shutters, ventilation flaps or slots on opposite sides are another way to ensure low-cost and efficient ventilation. Implementing this solution however heavily depends on the sensitivity of the seedlings as well as the construction of the house.
Electric ventilation: Where does the power come from?
The greenhouse should have a connection for power supply if programmable electric devices will be used. Models powered by batteries do not ensure a permanent and regular operation that is required for cooling the greenhouse. If there is no other way, it is also possible to redirect the power from the garden shed or house with the help of an extension cable.
As an alternative to an electrical connection you could also install a weatherproof (mobile) solar panel on the roof of your greenhouse and generate your own power right then and there. To ensure night operation of the fan the solar panel should be able to store some of the power collected during the day. If you only want to cool the greenhouse at daytime it is enough to acquire a panel without storage.
Compact solar-powered fans for your greenhouse include the fan as well as the panel. This combined solution is already available at reasonable prices, but it offers less control that devices with sensors. In most cases, solar fans only come with an on/off switch or operate automatically as soon as the direct solar radiation creates power. At night or on cloudy days operation is not ensured.
Both types (with or without storage) of solar collectors for use in gardens offer enough energy to operate simple fans. Those devices consume not much energy, and work with as little as 10 to 28 Watt.
The purchase price of a solar panel often more cost-effective than to install and lay cables underground. On the other, if you wish to use this power supply for other devices, such as lawn mowers etc., the latter option is more convenient for you. It is important to consider the pros and cons before making a decision.
Once the current is flowing: Which models are there?
If the manufacturer indicates a fan is suitable for use in outdoor areas you can also set it up in a greenhouse. The location of the device is stated in the item description, in case of any questions do not hesitate to contact the seller. Fans for outdoor areas or damp rooms are protected from rain and rust by weatherproof materials and a waterproof shell around the motor. The integrated components are usually easy to clean.
An IP code indictates protection from dripping, splashing and spraying water as well as high humidity levels. Even if rain cannot enter the glasshouse, humidity levels pose a risk to inappropriate models. For this reason you should pay attention to whether or not your device is allowed to be used in damp rooms! At least IPX2 protection against vertically falling water should be given. Additional protection codes keep high-quality materials safe from foreign bodies and touch (insects, leaves).
Also pay attention to the maximum ambience temperature, because heat can build up under glass.
Basic fans (free-standing or suspended)
Some models have useful timers that let you choose operation intervals of several hours. The service of those fans however requires switching them on and off manually. There must be an opening or outlet in the house so that fresh air can enter. Big ceiling fans with a large diameter are often impractical in greenhouses due to their weight and space requirements. It is still important that the fan provides sufficient air flow for the entire room, so the device should not be too small either.
Oscillating pedestal fans (swivelling from one side to the other) have the added benefit of ventilating the entire greenhouse. Even far corners are reached and all plants profit – plants with wind-pollination require moving air for fertilisation!
Air circulators recirculate warm air from underneath the ceiling through a tube back down to the colder ground where the plants are growing. This creates an even indoor temperature.
+ Additional effect of fans (all kinds): Pest cannot sit down on plants so easily due to the fresh air. The straight, upright growth of the plants will also be strengthened by the slight resistance caused by the airflow.
Small room fans for walls and windows
When breeding plants it is wise to employ a fan that automatically starts working once the ambience air reaches a certain humidity level. They are actually designed for ventilation in kitchens and bathrooms, but those fans are ideal for our purpose. These models‘ automatic humidity control operates with sensors and thermostats that are sensitive to water. For example, they can be programmed to react to humidity levels of 60%, 70%, 80% or 90% RH.
By default bathroom fans are supposed to be connected to a light switch, the flush, a motion sensor or a pull cord. For the special conditions inside a greenhouse controlled ventilation with humidity sensors is a good solution (check item description).
An additional timer ensures ventilation at regular intervals. The timer should operate independently from the time-delay relay (the relay is connected to the light switch, etc.). As the device is designed for continuous operation, pay attention to the power consumption to prevent unpleasant surprises on the next electricity bill.
Another benefit: Installation in pipes, ducts, outlets or openings in the windows or walls is easily done within a matter of minutes. It is also possible to add an opening to a window later on without too much effort.
Small room fans – Your benefits at a glance:
- fully automated control of humidity levels with sensors
- designed specifically for use in damp and humid rooms
- simple mounting, cleaning
- low acquisition costs
- space-saving
With our tips and tricks for ventilation in greenhouses we wish you a very fertile summer!
You want a blog post about a specific question? Get in touch and send us an email to info@creoven.com
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