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Proper placement of Insulation in Cathedral Ceiling

GeorgeP's picture

I need to insulate the cathedral ceiling.  The roof is constructed with 2x10 rafters, 16"oc.  There are collar ties at the top.  The ceiling will be finished with pre-finished 3/4" flooring.  For insulation, I plan on using 30RC batts without baffels or, if the building inspector allows, 30R batts with baffles.  My questions are how to properly insulate the upper part of the roof. The photo shows how much of the roof extends above the collar ties (not a lot).

- Should the batts, and baffles run all the way to the ridge vent or only to the insulation between the collar ties, leaving the part of the roof above the collar ties uninsulated?

- If the batts go all the way to the ridge is there a problem with also insulating betweent the collar ties?  Does it give any benefit?

I'm thinking of running the insulation all the way to the top just because it is such a small space and why bother with cutting it.  If insulating between the collar ties doesn't buy me anything R value wise then I wont spend the money to do it.