Open cell (semi-rigid) spay-applied polyurethane foam insulation systems (0.5 lbs/ft³) are made up of million of microscopic cells that simultaneously insulate and air-seal. They make residential and commercial structures more energy efficient, comfortable, quieter and less dusty. Open-cell insulation is applied as a liquid, which expands into a semi-rigid mass, automatically sealing off drafty areas such as baseboards, headers, sill plates, around windows, doors, electrical outlets, pipes, etc. It also minimizes uncontrolled air leakage throughout the building envelope (wall, ceilings, etc.), thereby reducing energy losses and the possibility of mold, mildew and premature decay.