I was just reading a thread about sweating at night in diapers. I've had that experience as well. After doing much research and talking to doctors, I've found that...contrary to logic...wearing some night nights actually stops me from sweating. It's to the point where if I wake up wet...from sweat...the wife will tell me to put on some Jammie's. Give it a try. I've tried air conditioning, fans, pillows, breathable blankets...but they didn't work. Wearing pjs, even over thick, wet diapers, does.
Hope this helps!