As Green Building Professionals, http://www.greatlakescarpentry.com/ we consider Building Science to be the most important consideration during the design and build phase for every project we take on.

We consider Joe Lstiburek, from Building Science Corp. to be the godfather of building envelope science. We own and have read all of his books and practice his teachings during the course of construction of all of our projects.

We believe that energy efficiency is the cornerstone of green building and that in order to build safe, durable, energy efficient homes and remodels, we need to understand and implement building science principles, disciplines and best practices.

Follow this link: http://bcove.me/249e285n to an excellent video on roof insulation and ventilation, done right.

Joe is very forthcoming with information and sound advice.
Follow this link to his website for more. http://www.buildingscience.com/

Enjoy