For our temperature tests we loaded the system for 10 minutes using Prime 95 and recorded the CPU temperature using CPUID HWMonitor. We then restarted the system and left it idling at the desktop for 10 minutes before recording temperatures. The temperatures recorded are based on an ambient temperature of 20 degrees C.
The NH-U12S showed pretty good thermal performance in our tests and was only a few degrees behind the larger NH-U14S. We found that having a dual fan configuration improved temperatures by a significant margin.