For more information, visit: br Cooling is necessary for the indoor grower to maintain a safe and desirable temperature for the plants. This varies depending upon the strain of marijuana, the number of plants, and type of lighting being used. For the home-grower, cooling systems are usually not necessary, ventilation is typically enough. However for the commercial scale grower using “closed growing environments,” cooling systems are a must-have. A closed growing environment differs from the traditional grow room set-up in that it does not "connect" to the external environment and runs on a closed loop. This allows the grower to have greater control on the environment and improve the conditions for plants to thrive.