ceiling insulation cost
1 A rough estimate for hiring someone to blow insulation into a flat roof, cathedral ceiling or wall cavities is $2-$3.50 a square foot, or $1,000-$3,500 for filling 1,000 square feet of empty wall or roof space. That's $400-$1,800 for an 800 square foot space, with a typical attic insulation averaging $750-$1,100. 2  Do-it-yourself materials for roll-out batting in an open attic can run $100-$500, depending on R-values, attic size and other factors.