In print, the addition of space around dashes is a question of esthetics; in the United States, it's common to add some space around tight dashes, but the practice can vary in other countries. You'll occasionally see a full word space added before and after dashes in print, but if the font in question has a large word space value (as many do), it can look too open. I personally don't like tight dashes and use the kern function to have complete control over how much space I add. Whichever method you choose is a question of taste, as either is an accepted typographic practice.