About half of all homes have attics with insufficient insulation. A good rule of thumb is that if you have less than six inches of insulation, you need more. In general, you would benefit from up to 12 inches of attic insulation. In the attic, you should insulate at least to R-30, or six to eight inches. Insulate walls as much as their thickness allows, and floors to at least R-19, or six inches.
Cellulose insulation is recommended.
4 Seal other Air Leaks Air infiltration from the outside is another huge energy loser. A tight house sees a complete air exchange only once every two to three hours. Caulk everywhere the brick or stone meets the walls and ceilings. Cover the opening with tight-fitting glass doors. If you have an attic fan that you don't use, seal the opening with a temporary or permanent cover.