Overhead insulation refers to the layer of insulation covering the top floor ceiling. This layer should be a minimum of 6 inches thick over the entire area. By carefully insulating this section of the structure, heating costs can be reduced by 10 to 15 percent. Air conditioning costs in the summer will also be reduced. The overhead insulation should be checked in an older structure, because some building contractors will only install 3 to 4 inches of the material. Adding an additional 2 to 3 inches is not only easy to do, but well worth the effort.
Tacks or staples can be used to attach batt or blanket insulation flanges to the wood joists supporting the ceiling. Blanket batt, and loose insulation require a water vapor barrier placed between the insulting material and the ceiling lath. Reflective insulation is attached to the middle of the joists so that there is an air space both above and below it. No water vapor barrier is necessary. When using reflective insulation, additional protection is required for the insulating material, which usually takes the form of lath and an attic floor.