Attics are the greatest source of home heat and cooling loss. Use enough insulation to go higher than the floor joists (about 12-15 inches thick). It can be rolls, batts, rigid boards, loose fill, or spray foam, as long as it is rated at R-38 or higher. Insulating hot water pipes can also save on water heating costs.
This tip is brought to you by Cheryl Frank, Greece Baptist Church.