I discoved the original certificate in attic stating who installed and the R value. House is mid-century 1965'ish. I need to upgrade, or remove an install new insultation in the attic. The house is stick built using 2x4's, ceilings are 24oc. Would you recommed covering over existing insultation OR removing it and putting in new paper faced batts approptriate for the region I live in? Roof is not insultated.