Seven years ago, Georgia led the nation. Yep. We were the first state to adopt an energy code that made blower door testing mandatory. All new homes built in the state had to show through performance testing that they had an air leakage rate of less than 7 air changes per hour at 50 Pascals of pressure difference (ach50).
from Building Science http://www.greenbuildingadvisor.com/articles/dept/building-science/difficulty-updating-georgia-s-energy-code