Yes an RHP will throw heat above it as well as below it. On one of my melamine stand-alone enclosures it's a bonus, as it creates a nice 90-92*F hot spot if you put a 34-qt latch box tub on top of it. The PVC enclosures have some wood boards between them to allow airflow between the enclosures, so the enclosure above an RHP doesn't overheat.