Sleepers and Winter

Might be a stupid question. My LO is 5 months and sweats like no other. We always have to have a portable fan anywhere we go or else he would flip out. 😂

He used to wear just a onesie, socks and a sleep sack. The house we are renting is crazily built so the main AC and Heat doesn't go all the master bedroom and that's where we all sleep. We would usually use a portable heater during winter and use fans during the summer.

Anyways, he is now only wearing one of those sleepers. He has been ok in terms of body temp. The monitor says the room ranges from 72-74°.

What should he wear during the winter? Just thicker sleepers?