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.
Trees that lose their leaves in the fall (i.e., deciduous) are the most effective at reducing heating and cooling energy costs. When selectively placed around a house, they provide excellent protection from the summer sun but permit winter sunlight to reach and warm your house. The height, growth rate, branch spread, and shape are all factors to consider in choosing a tree.