Cellulose insulation is a plant-based insulating material used in wall and roof cavities to separate the inside and outside of your home thermally and acoustically. Cellulose keeps the heat in and the noise out, providing an excellent sound barrier. Cellulose is able to get around pipes, wires and other items that may be inside the walls. Cellulose leaves few air pockets that can reduce the overall efficiency of the wall. Cellulose is up to 85% recycled paper waste material with the remaining percent made of boric (fire retardant) treatment that provides a Class-1 fire rating, making it a safe choice.