At the moment the heat and humidity content of the outside air during the daytime can be higher than the growing room air In this type of situation it is better to use as little of this "unsuitable" outside air as possible by for example setting the CO2 to a higher (maximum) value This releases more cooling capacity for the room climate with beneficial effects on evaporation

At night when the heat and humidity content of the outside air is lower than the growing room air it is better to use as much of the "suitable" outside air as possible by for example setting the CO2 to a lower (minimum) value This means there is less cooling capacity required for the room climate which saves energy

Adjusting the CO2 value can be done manually or automatically via the climate computer settings If automatic adjustment is chosen do not forget that the settings are based on the outside RH measurements If the measuring sensors are too dry control at night may also be based on the maximum CO2 value which can place an unnecessary load on the cooling system Good (weekly) maintenance to the outside RH measuring equipment will also help save cooling energy

Jan Gielen Specialist climate & energy C point