To find out if you have enough attic insulation, measure the thickness of the insulation. If it is less than an equivalent of R-30 (about 10 to 13 inches), you could probably benefit by adding more. Before insulating, seal any air leaks and make roof and other necessary repairs. If it is located in a conditioned part of the house, also remember to insulate and air seal your attic access.

INSULATE

and air seal any knee walls -- vertical walls with attic space directly behind them -- in your home as well. In addition, if you're building a new home or remodeling, make sure any attic decking that provides additional storage space or a platform for a heating and/or cooling unit or hot water tank is raised above the ceiling joists to leave room for adequate insulation. 

If the air distribution system is not within the conditioned space but within the attic, insulating the rafters will enclose the distribution system. Finally, if you live in a hot or warm climate, consider installing a radiant barrier in your attic rafters to reduce summer heat gain