On 12/21/2004 12:19 AM US(ET), effi took fingers to keys, and typed the
following:

"willshak" wrote in message
...


On 12/20/2004 8:22 PM US(ET), effi took fingers to keys, and typed the
following:



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



They make formed foam spacers that go between rafters that will keep the
insulation away from the roof sheathing.
Check at the big stores.



considered those, they probably won't be structurally strong enough in this
application

also considering 4" of fiberglass insulation with 1 1/2" or 2" pvc,
perforated along the length by drilling lots of holes, run centrally inside
the 4" fiberglass to provide air circulation instead of 1" open space above
2.25" of insulation


I've already responded to this in another message, but I just had a thought.
Instead of all these efforts to keep the insulation away from the
sheathing with Rube Goldberg ideas, how about you nail 2-1/2" x 2-1/2"
strips of wood to the current 2 x 4 joists, so that they are 2x5"
joists, and then use common 3-1/2" insulation stapled to the 1-1/2" faces?
That will give you a 1-1/2" gap between the insulation and the sheathing
which is the recommended gap.

--
Bill