Ventilator - with speed control or without?

When customers ask us if they should get a ventilator with speed control or without it, we almost always say controllable ventilators are better. Why?

In short: they’re more practical. Estimating the optimal ventilator speed setting upfront isn’t easy. There are many things you need to consider, like the temperature inside the grow tent, the temperature outside it, placement (you’ll need to lower the temperature less in a basement than in an attic), humidity and many more.

Furthermore, the temperature inside the grow tent changes during the cycle (and the day), and the ventilation should compensate for it. The temperature outside the grow room also changes, so the ventilator takes in warmer or colder air. It’s hard to react to these changes without speed control. It’s always best to have more than one option.

What’s more, a regulated ventilator doesn’t run at full speed when it’s not necessary, so you’ll save on energy.


Some speed control has hysteresis, so it doesn’t react to temperature changes by simply turning on and off. Instead, it slightly increases the ventilator speed when the temperature rises to compensate for the difference. If the temperature keeps increasing, it speeds up again. That way, the temperature stays closer to the pre-set ideal temperature. 

TIP: Is the regulated ventilator always at full speed? You may have a lower ventilator capacity than you should have, or it’s taking in air that is too hot.

These are the main reasons why we recommend ventilators with built-in speed control or controllable ventilators you can connect to a regulator. Of course, if you're familiar with the space you’ll be using and know exactly how much ventilation it needs, a single-speed ventilator won't pose a problem, and many growers use them.

It’s easier to tailor the climate to the plants' needs with a controllable ventilator. It increases your chances of getting good results.

And which particular fan do we recommend? The tried and tested ventilators by PrimaKlima, without a doubt. The PrimaKlima PK125-TC (400m3/h, 125mm) ventilator with a built-in thermostat is one of the bestsellers. 

Choosing a ventilator isn’t child’s play, and general advice often isn’t enough. We will gladly consult you individually at and help you pick the ventilator type and strength which will be perfect for your setup.

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