As a rule of thumb, you should control your environment to in the following ways:
- Temperature: 24oC- 28oC (day/lights on) or 22oC – 23oC (night/lights off)
- Humidity (RH): 70 – 85% (propagation), 65 – 75% (veg), 45 – 65% (flowering)
- CO2 level: 1000ppm – 1200ppm for up to 40% faster growth
Raising the temperature of an area is normally relatively easy. Use one of the heaters below, add HPS bulbs to the lighting array or simply turn your heating up!
Different types of system
The “open” or “ventilated” type of system described above certainly works, but it does have its disadvantages. Because the air is constantly being replaced, it can be difficult to maintain a particular relative humidity, or to increase the CO2 level in the air which can greatly increase plant growth rates. The air temperature and the relative humidity together create an effect called Vapour Pressure Deficit (or VPD for short). Getting the VPD level correct is one of the major keys to getting the most from your grow, and the CO2 level is one of the others. You can read more about VPD Here.
In warmer parts of the world, something called “closed-loop systems” have gained enormous popularity, particularly with commercial growers. Closed-loop systems involve having a completely sealed grow-room. No air is extracted out to or drawn in from outside the sealed grow-space. Instead, the temperature is kept within the right range by a heater and an air-conditioning unit. Humidity is controlled by the use of dehumidifiers and humidifiers. Plus, with no air being drawn out or in, the use of CO2 supplementation becomes well-worthwhile. CO2 levels can be supplemented with a controller and a bottle: