I'm replacing old insulation in a 1962 cape cod style house in the Baltimore area and trying to determine if I need vapor barrier. The more I research, the more complicated the answer becomes. The IRC has several zones defined that help in guiding this, and a map that shows where they are. But zone 4, which includes my area, has several subtypes (which aren't shown on the map) and I have no idea how to find out which I'm in. How can I find out exactly what zone I am in?