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Verti-Fan practical experiences 2010

Findings of independent cultivation advisor Krijn Buitelaar.

In all companies, the exhaust opening is 40 cm above the ground surface. In a few companies, additional fans are present, mainly in the direction of the walls. In the beginning the revolutions are temporarily lower, but generally they run at setting 4 or 5. When ventilating, some continue to operate the fans and others turn them off temporarily for open windows, temperature or humidity. In the winter and spring, the fans generally operate 24 hours a day, but less in summer.

Air windows
When ventilating, the fans stay on for longer. The minimum window opening is generally the same or sometimes slightly smaller. Squeezing the air windows to save CO2 does not occur frequently. Keeping the windows closed after mid-August depends on the type of plant. Strawberry growers want to let the cold in.

Half of the participants turn off the fans when the shutters open. The shutter takes between 10 and 20 minutes to open.

Heating pipes
The minimum pipe temperature in the winter and the spring was about 45-50 °C. Later a somewhat lower minimum pipe temperature was maintained, but one grower preferred a higher pipe temperature to stimulate evaporation.

The severe winter meant that the horizontal temperature distribution was less good than last year. The start of the harvest was thus uneven. Later the temperature distribution was good. No other temperature was set in order to prevent disease. Whether or not Verti-Fan saved energy could only be assessed at Prominent; here there was a saving of 10%.

A higher humidity was often observed, sometimes above 90%; hardly ever were any measures taken against this because no disadvantageous consequences were observed caused by the vertical air movement.
Damping-off of fruit appeared to a slight degree in a number of cases.

The number of hours in which it is dosed per day has not changed. No data is known about usage.
It is possible that the content is somewhat higher in late summer because of more limited ventilation.

Water dosage and fertilisation
Generally the growth of the plant was no different than without Verti-Fan, so that water dosage and fertilisation did not have to be adjusted.

Plant condition, production and fruit quality
Initially, the plants were less consistent than last year. The severe winter caused more cold corners. Later, the consistency was good.
Sometimes the plants seemed more heated. Prominent adjusted to this which led to a slight increase in production.
In common with last year, one eggplant grower found the fruits somewhat heavier and compacter.
In strawberries, the number of torn fruits declined sharply and production increased.

Disease, pestilence and abnormalities
Mite, thrips and louse appeared quite early but were easily controlled.
Later, mite and thrips played a small role, but white fly was regularly observed for which a link with Verti-Fan is occasionally seen.
Botrytis only occurred occasionally, if at all, and flower mould on egg plants was very limited.
In flowers, fungal diseases were notably less.
The use of pesticides was the same or slightly less.

Measurements and observations
The leaf temperature was closer to the ambient temperature.
At Prominent, many observations were made in comparable departments with and without Verti-Fan, which improved insight into the effects.
If the CO2 from the boiler were to be cooled, CO2 would rise less quickly and the yield would be improved.

A few growers vacuumed or wiped the leaves for a better air displacement. A tomato grower erected screens near the gutter for the first five weeks after planting to prevent plant movement. An egg plant breeder will use more substrate for the next crop because of the greater growing strength. One grower is planning to operate the Verti-Fan based on the outside temperature. Two growers found that the hoses polluted quickly.
Growers with one or more years experience with Verti-Fan feel that continuing to gather experiences has no added value. This is more or less true for the user meetings. Adjustments and improvements can, according to personal insight, be applied at their own company.


  • The exhaust height is standardised at 40 cm.
  • The majority of fans operate at position 5 and are turned off at a certain degree of window opening.
  • When opening the energy shutter, the fans are increasingly allowed to continue operating.
  • Thanks to the severe winter, the horizontal temperature distribution was not optimum, but clearly better than without vertical ventilation.
  • At Prominent, it was shown that energy savings are possible with Verti-Fan by maintaining a lower pipe temperature.
  • With Verti-Fan, the crop became more active with more evaporation and a somewhat higher humidity, but that is not disadvantageous.
  • With the Verti-Fan, the incidents of fungal disease, particularly in flower horticulture, decreased.
  • The damping-off of fruits rarely occurs.
  • The somewhat better growth and the lower infection rate can give a higher production.
  • Thanks to the many observations throughout the cultivation at Prominent, valuable information has been obtained.
  • Company excursions and user meetings are less useful for growers with one or more years of experience. Plant-oriented meetings can certainly be valuable for beginner growers with Verti-Fan.

Krijn Buitelaar
Independent Cultivation Advisor

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