Answer: The industry standard from AHSRAE is between 64.4°F and 80.6°F (18°C to 27°C), with the relative humidity (RH%) between 45-50% for server rooms
However, there are many variables you can consider when determining the correct server room temperature, such as the number of servers you have, their manufacturer designated operating temperatures and the load being placed on the servers. Many data centers and server rooms waste energy overcooling, especially during “off-peak” hours where server load capacity is down. The harder the servers are working, the more heat they generate, and vice versa. So, through the use of intelligent controls and monitoring systems you can maintain the optimal server room environment based on the loads being applied.
The ASHRAE recommended standard ensures there is leeway given for variations in CPU loads. It allows them to run a little hot for short periods of time, without unnecessary overcooling.
The use of thermal map sensors on server cabinets, as well as power meters to check your PUE numbers allows you to fine tune the server room environment for optimum conditions. Maximizing your PUE, while not putting servers under threat of thermal shutdown.