Every contractor I talk to gives me a different story.

What we have now is a 30 year old shake roof in poor condition, likely with no insulation. It's tongue and groove decking, some fiber board, then felt and shake shingles.

What we want is a very energy efficient roof -- the problem is our open beam ceiling.

How high an R-value can we practically achieve? What kind of roof system do we need?

You could have a look at Vented Nailbase.

http://www.jm.com/roofing_systems/builtup/products/RS_5147_VentedNailBoard.pdf

Phil Felber
http://www.roofing7.com/