I have 6 inch by 18 inch by 20 feet cavities between roof tiles, wood beams and plasterboard in a sloping roof above a lounge area that I wish to insulate. I need a relatively heavy bead that can be poured into the cavities (access is in a loft over the opposite side of the house) and which will slide down to the bottom of the slope. Polyethyene is too light and sticky. Is there a polyproprylene bead available that would be suitable and if so where can it be obtained?