Black stove pipe (and furnace pipe, for that matter) should be securely fastened together at each joint with no less than three sheet metal screws or pop-rivets. Stove and vent pipe should be inspected at least yearly, and replaced when signs of rusting or wear are evident.
Install additional attic insulation at right angles to the previous layer. You don’t have to use the same type of insulation – it’s fine to use batts or blankets over loose-fill, or vice versa. Upgrading from three inches to 12 inches can cut heating costs by 20 percent, and cooling costs by 10 percent.