Insulation, Radiant and Vapor Barriers - rigid polyiso ?

do to space requirements, I am thinking about using cellulose or fiberglass in my 2x4 vaulted ceiling joist cavities, thenusing polyiso rigid board to get the R value up to the required R-without taking up as much space as conventional insulation. Whee do I find someone who installs this kind of insulation? Or does anyone have other ideas?

Are you thinking about puting the rigid board on the inside (behind the sheetrock), or outside (between the rafters and the roof sheathing)?

Either can be done. The drawback on the inside is that it makes getting a smooth, even sheetrock ceiling very difficult. The drawback on the outside is that it must be placed before the sheathing, and you can't walk on it to place the sheathing. An option would be to put on sheathing, then foam board, then top with more sheathing - doubles the cost of sheathing. Obviously, longer fasteners must be used in either case.

thanks for your reply! who normally would do the installation? roofer? insulator? sheet rocker?
The residential insulation contractor I have spoken with seem to do only blown in or batts.....

Probably your carpenter, but it could be your roofer if it's on the outside - depending on what arrangement he has with your carpenter.