According to research by the US Department of Energy, the proper amount of insulation can pay dividends for you AND the environment:
Insulating a home provides several benefits. The primary benefit is savings on the cost of heating and cooling the home. Up to 70 percent of the energy used in an average American home goes toward heating and cooling, and increased insulation reduces that expense. Another benefit is moisture control, as proper insulation can reduce condensation that would otherwise occur in interior spaces of the home. Insulation can also be used as a form of soundproofing, as the dense nature of insulation helps dampen sounds within the home. Insulation is noncombustible, though not completely fireproof, and therefore reduces the speed with which a fire in the home can spread.
In the Louisville, KY area the recommendation for R Values is between R18 and R60. For loose fiberglass insulation that means between 13 and 22 inches should be in your attic. Up to 45% of the energy you pay to condition escapes through the attic of your home. That adds up to very substantial cost savings when proper levels of insulation are installed. We use Owens Corning brand blown fiberglass insulation and can increase the R value of insulation in your attic with no mess. Our equipment stays outside with only a tube running inside the home. We make sure that you have proper ventilation by installing baffles in between the joists to allow air to flow from the soffits up through the attic and out the roof or ridge vents. We make sure that any light fixture that is in contact with insulation is IC rated, or has a barrier installed.