Today’s walls, roofs, and floors are better insulated, tighter, and made with a much greater variety of components than they used to be, making them a lot more susceptible to moisture problems when they get wet. Compared to the old days, today's walls and ceilings are more complicated and can be very slow to dry.
_This podcast series is excerpted from a two-day class called_ Building Science Fundamentals _with Drs. Joe Lstiburek and John Straube of Building Science Corporation. For information on attending a live class, go to [BuildingScienceseminars.com](http://www.buildingscienceseminars.com/) This week Dr. Joe talks about enclosure design principles of energy efficient buildings_