wrote in message
ups.com...
Looking to board my attic for storage; it has some scrappy Rockwool
and joists are 4"x2". I was wondering whether to plant 2"x2" timbers
on joists to allow for greater depth of Rockwool, or maybe the
chipboard would provide enough extra insulation? Another thought -
better grade insulation material in place of Rockwool but in the same
4" space? Any ideas welcomed.

I would use the new multi-layer reflective stuff stapled to the inside of
the rafters. Much easier to do than foam sheets, and your loft would not get
as hot/cold.