My husband and I recently purchased a home. We currently have vermiculite in the attic. The space between the 2x6's is filled with about 2" of the vermiculite in some areas and about 6" in others. We are planning to use the attic for storage and would like to upgrade or add to the current "insulation" and then screw down some plywood on top (so we don't step through accidentally). What is the better $ R-value rate?... Styrofoam, pink or something else? What has the better R-value/inch? Thank you in advance for any information you could give us.