I recently purchased an older house in Bozeman, Montana.  Noticed that cold air filters down from a cedar covered open ceiling in the main living room.  Also noticed that this ceiling is (by layers–inside to ourside): a. cedar siding, b. fiberglass insulation without vapor barrier, c. roof sheating and d. roof (cedar shingles). 

Have read some of this forum and have concluded that to insulate this attic area better that I could/should 1) place vapor barrier in attic on warm side of attic, 2) possibily attach 1 to 2 inches of rigid insulation on ceiling underneath the cedar siding and 3) make sure ventilation is adequate in attic.                 However, I have also read the cellulose insulation might be better, but that it is messy and that I would need to pack this cellulose in the attic and eliminate any form of attic ventilation (and of course eliminate the need for a vapor barrier) to maintain the R value or to improve the R value over fiberglass insulation.   

What do you folks think????????????????????   And if I did use cellulose for insulation what about the summer months when it gets hot and there is no attic venting.

New member and hoping some folks will answer as I learn lots about house stuff!!!!!!