Heater placement

Cooling will come, probably not soon but it'll happen. Sealing for airleaks in a 40 yearold garahe won't happen. I'm not willing to spend that kind of time, nor effort and money, on that sort of thing. Insulation is coming soon, like this year soon. The heater ill probably use is a mr heater type unit. I need more research on it tho. I don't want a heater that is really loud like my forced air kerosene, but I understand that when you have a blower on a shop heater, there will be some noise. I just want to be able to conversate witjout hollerin. I've read there are areas that don't specifically need the vapor barrier. Why would that be? I'm in Wichita, Ks and will be using it, but I'm still curious as too why one would not use it.