Tom writes again from Media, Pennsylvania: "I put the flooring down for storage. I can't put the insulation down on the floor. So knowing this, should I insulate the rafters?"

Answer: No. But you can make sure the items stored in the attic are spread evenly over the entire floor. Seriously, if you have boxes and other objects on the floor, they will provide some R-value in the areas where they are placed. You will need walkways, of course, but I'm sure you get the idea. Since your attic is not conditioned, i.e. heated or cooled, it should be ventilated to avoid trapping moisture in the attic and to keep the roof deck dry. For information about how much ventilation you should have, check the Owens Corning website. And since the attic is ventilated, the only place that needs to be insulated is the floor of the attic because it is at the point where heat can move between the attic and the rooms below. The idea is to insulate to keep heat or air-conditioning in your living space. Insulating other areas will not give additional thermal control.