88 square feet per bag or 704 square feet in 8 bags
If you are referring to the cavities between the first and second floors, yes you may use this material if the cavity is 10 1/2", if you put into a cavity that is smaller than 10 1/2" you will be reducing R Value.
Knauf’s EcoBatt insulation provides excellent acoustical properties and will reduce sound transmission when properly installed in partition walls and acoustical ceiling and floor systems. Knauf acoustical/thermal insulation can improve STC ratings in wood stud construction by 3 to 5 points and metal stud construction by 8 to 10 points depending upon the complexity of the wall configurations, R-values and layers of insulation. Your total STC rating is determined by your complete wall construction.
11 pieces in a bag or 88 sq. ft. per bag
10 inches thick.
Thirteen batts for r30
Most likely, but the R value could be decreased by it not being spread in an aerated method.