My son (17) does the same thing! I ask him "aren't you hot?" His response in an annoyed voice, "No, Mom, I'm not hot." It has been hovering close to 100 degrees here and humid. He is very hot natured anyhow (used to refer to him as my little heater when he was little), so I can't understand how he wouldn't swelter in the hoodies and sweatpants. I've since learned just to leave him alone about it. He wears the same clothes for days in a row and he also does not like to wear underwear. Gave me a speech about how wearing underwear kills the sperm. So I just let it go.