C & E wrote:

If anything you would be wanting to *add* insulation to the attice which is
the point of the greatest thermal loss. My blown-in was done by the
previous owner and on top of the glass insulation. Over the past 25 years
it has settled and I have rolled out new batts perpendicular to the joists.
Now, if I were in your situation and wanted to create storage for light
loads in my attic I would make 2x4 standoffs to a height just greater than
the insulation that you have or intend to put down in the future. I would
connect them with 2x4s and top with 3/8" CD ply. JAT
Chuck

Andy adds:

A good idea, and not very expensive or hard to implement..

Remember tho, that NOTHING stops air from moving like a solid
barrier. When you put the plywood floor down, it makes a solid
barrier
on TOP of the insulation, which means that air will no longer waft up
thru the insulation...

So any R factor you lose by comressing the insulation will be offset
by the fact that you are putting a solid barrier on the top side,
which
means there will be practically no air circulation..... In my
opinion,
the decrease in Rfactor, if there actually is a decrease, will be
negligible for only a couple inches of compression. In fact, it
might
even get a little better, but one would have to experiment to know
for
sure....

If air circulation was NEEDED in the insulation to prevent moisture
buildup, that might cause a problem , depending on which side of
the insulation the high moisture side is on. But it probly wouldn't
bother you much in the technique you are suggesting...

Best of luck on your project.

Andy in Eureka, Texas ...... P.E.