would like to create a cathedral type ceiling in a small area of 24" on
center roof rafters 3.25" thick

within the 3.25 inches thick want: 1" airflow space; and 2.25" insulation

how can the 1" thick airflow space (between 2.25" insulation and underside
of roof decking, plywood) be created?

seems just putting 2.25" thick of insulation without some means to keep the
1" airflow space open might be a mistake

have considered chickenwire with small 1" thick blocks of wood glued to
underside of roof decking every foot or so to keep the space open