What you are talkibng about is essentially the concept of 'frames' where the browser viewport is split between multiple sections each of which is a seperate web page. Frames became quite common for a while because they allowed greater efficiency as you say, by not requiring full page reloads, however they raise all sorts of other issues and are generally avoided by smart developers now.
However for what you want it would be possible to use an iframe which is like a frame embedded within a page. These are not quite as bad as full on framesets and would do what you want.
That said, it is only really worth doing if the part of the page that you wont be reloading is large enough to cause performance issues, otherwise I would be tempted to stick with a single, frame free, page personally.