Fundamentals - References
Further reading from the guys that study building science are saying.
Dr Joseph Lstiburek and Dr John Straube at the Building Science Corporation
There are many different ways to build the walls for a house. Whatever design and materials you choose, it is important to draw a diagram to show the vapor barrier and how the wall on either side of the vapor barrier will dry out after it becomes wet. A foremost authority on proper water vapor design is Dr Joseph Lstiburek at the Building Science Corporation and he has published lots of useful papers such as can be found here. He has also drawn up vapor diagrams for lots of different wall designs (although not for concrete+polystyrene walls). You can see some of his diagrams and read his good words here and here.
A good paper on rain screening and drainage planes by John Straube who is the other expert at the Building Science Corporation can be found here . It describes 3 strategies for keeping rain from penetrating walls.
The building science guys' recommendations on insulation thickness can be found at http://www.greenbuildingadvisor.com/blogs/dept/energy-solutions/how-much-insulation-needed .