If the aircon is set to 16c and heater is set to 21c it doesn't mean the room temperature is actually at that!
Your also not staying in the house all the time. When you go out your exposed to the elements and maybe your body is trying to recover from that even in a warm environment.
Best way to combat the cold is jumping into cold water. IE jumping into the ocean or swimming pool.
Cold water is very good for circulation and lack of is why older people feel the cold more. It also helps to prime the immune system which will help to keep you young.
