In any enclosed environment where there are a lot of computers being used, including server rooms, the temperature is critical. All of the equipment has a maximum temperature at which they can operate anything above this and their efficiency is reduced or thermal shut down takes place. So it is important that server rooms are kept at a stable temperature. But it is also important that humidity, which can be a problem, is controlled at the same time.
So what this means it some kind of air conditioning is provided to the room so that a constant temperature can be maintained no matter what the conditions outside are like. Plus it needs to dehumidify the room to allow removal of any excess humidity.
The size of the air conditioning system used in a server room should be of a capacity that can cope not only removing the heat generated by the computer equipment in the room but also natural heat energy. Also as this equipment is in use 24 hours a day, 7 days a week it must be a unit that has been designed with a continuous rating rather than those that are used for domestic use and will only be used infrequently.