Looking for good insulation solution for cathedral ceiling. Plan is to have rustic look, with rafters exposed or partially exposed. Rafters are 2x6. Lots of sun, so looking at radiant barrier, but need decent R value too.
Insulation has recently become a big issue for me in building a new home. I researched cellulose and batt. A R-30 to R-38 batt in the cathedral ceiling is good. If you are planning to expose part of the rafters make sure there is still an air space above the insulation for the attic to breathe.
You are going to have a hard time doing this and getting very much insulation value. As Rocko says you need to have ventilation above the insulation, open at the bottom and the top to the outside. This only leaves you say 4" of space to insulate. If you want exposed rafters, you have even less. For a 1" exposed rafter and using 1/2" drywall in between the rafters with a 1/2" stop to hold the drywall in and trim the edge, you're down to 2". You could put spacers between the insulation and the deck to screw the drywall to, this would save you 1/2", but at best (4") you're gonna get r-20 or so with rigid ins.
Where are you (hot/cold?) Are you doing this with a permit/code?
Perhaps you'd be better off adding some 'faux' beams to the inside after all the drywalling is done?
Tell us more about the situation: size of room/building; use of; pitch of roof; height of walls; location (geographical) etc.