Your attic is a great way to start saving money. It's a fact that heat rises and when looking at adding insulation most people think of adding more to what they already have. If you have to add 6" of insulation to what you already have, that must mean that you're losing heat through the existing 6". So why would you want to put more of a material that only slows down heat loss/gain on top? By installing Low-E Insulation under your rafters you're stopping the heat gain in the summer as well as helping to keep it in during the winter months. This also helps in areas where ice damming is a bad problem. Ice damming occurs when the snow on a roof melts at a rapid rate, the moisture then wicks under the roofing material only to freeze yet again. Ice and water shields only patch a problem. Low-E helps solve it! Low-E stops heat gain/loss! Unlike mass insulations Low-E will not absorb heat, it will reflect it. One layer of Low-E under your attic rafters will reflect the heat that is rising from your living area. This will slow the melting process down which could help save your roof and add a few years to it.