One important alternative to fiberglass (link) insulation is cellulose. Cellulose is installed with machines that blow it into attics or spray it into wall cavities. Cellulose is made from shredded newspaper and is a good insulator because wood, from which the paper is derived, has a heat-resistant cellular structure. Typical R-values range from 3.5 to 3.7.Cellulose loose-fill offers the same benefits over fiberglass blankets as fiberglass loose-fill does: it is more effective at insulating an entire space because it can fill oddly shaped spaces and let less air through. In spaces like attics where the insulation rests on the floor, dry cellulose can be blown in, while in vertical spaces like wall cavities the shredded newspaper can be purchased that is dampened and sprayed into place to ensure even, effective application. This technique is used more often in new constructions.

R-value is a measure of a material’s thermal resistance – the degree to which a material allows or does not allow heat to be conducted through it. In our context it applies to the insulation used to keep houses warm in the winter and cool in the summer. It’s measured both by the thickness of a given insulation material and by the structure of that material, so 2 different types of insulation with the same thickness can have different R-values. Comparing the R-values of various types of insulation is one of the most important ways to determine what type of insulation to use, and how much.
If a home had no insulation at all, the thermal resistance would be measured by the amount of air within the wall cavity, the air would have an R-value of 1 per inch (extremely inefficient). Fiberglass, a common type of insulation, ranges from an R-value of 2 to 5 per inch, depending on the type. Although R-values are measured by thermal resistance per inch (like an R-value of 3 per inch), the reference to thickness is usually not used (so instead we just talk about an R-value of 3).
As we’ve said before R-values and insulation make up only one of the two parts of the “envelope.” The other equally important component of the envelope is Air Sealing.

Insulation is material that essentially serves as a barrier between your home and the heat or cold outside. Good insulation will conserve the heat within your home in winter, and will help keep heat from entering your home in the summer. A material’s ability to do this is measured by its R-value. There are many types of insulation, and many places in your home to put it.