Is adding a radiant barrier while replacing a roof worth the extra cash?

Question

I have a small attic space at the apex of my house above the second floor and a larger attic space above my garage. My dining room and living room both have high vaulted ceiling with no apparent accessible attic space. I have read that raidant barriers need close to 1" or more of air space to work efficiently or they can possbily conduct heat into the adjoining structure one is trying to insulate. Is it best to add radiant barrier to my accessible attic space vs. radiant barrier to all roof decking?

Answer 1

Here are a couple of links that may help:

http://en.wikipedia.org/wiki/Radiant_bar...

http://www.ornl.gov/sci/roofs+walls/radi...