Excessive sweat

Is it normal for guys to sweat a lot at night? I’ve been with my fiancé for 5 years now and I really can’t remember it ever being this bad. For the last 6 months to a year he’s been sweating so much at night that the sheets end up being so gross. They get drenched and smell disgusting. I used to wash the sheets once a week and now I feel like I have to wash them every 2-3 days. What could be causing his excessive sweating? I realize it’s summer but this has been going on for a while and our house doesn’t get that hot. The only lifestyle change is that he’s been vaping for about a year. He’s also not over weight, he’s actually really healthy.