Adding loose-fill requires professional equipment. Naturally, this increases the cost. But, if you need more insulation in exterior walls, it may be your only option. They can be cut to fit and even provide some structural support. The boards are made of expanded or extruded materials and can be used in walls, ceilings and confined spaces.
Rigid foam represents the high tech end of insulation products.
They're easy to use and offer a high R-value for the thickness required. Generally, the first place you'd want to add insulation is in your attic. And it's easy to tell if you would benefit from adding some. Just measure how deep the insulation is. If it's less than 5 or 6 inches, you should add insulation.