A few factors determine how much attic insulation you need in total, and R-value is only a part of the equation. In addition to hitting your energy efficiency goals in terms of R-value, attic insulation also plays a role in keeping moisture, air pollution, noise pollution, and the like out of your home. Depending on what problems you have with your attic, filling small nooks and crannies with the right kind of insulation might be more important than hitting your target R-value — or at least, just as important. If you have goals beyond energy efficiency and keeping heat from passing through your attic, be sure to speak with experts about your goals and needs.