Blanket insulation is the most common and widely available type of insulation; it comes in either batts or rolls. Batts are made to fit between the wood studs that form your walls, were as continuous rolls can be hand-cut and trimmed to fit as needed. They are available with or without facings, (such as Kraft paper or foil) to act as a vapor barrier. A facing also helps facilitate fastening the fiberglass batts to the stud walls during installation.
To maintain your homes comfort level; the heat lost in the winter must be replaced by your heating system, and the heat gained in the summer must be removed by your cooling system. Properly insulating your home will decrease this heat flow by providing an effective resistance to the flow of heat. Installing more insulation in your home increases the R-value and the resistance to heat flow. In general, increased insulation thickness will proportionally increase the R-value.
An insulating material’s resistance to conductive heat flow is measured or rated in terms of its thermal resistance or R-value -- the higher the R-Value, the greater the insulating effectiveness. The R-Value depends on the type of insulation, its thickness, and its density. When calculating the R-value of a multilayered installation, add the R-Values of the individual layers.
Unless your home was specially constructed for energy efficiency, you can probably reduce your energy bills by adding more insulation. Many older homes have less insulation than homes built today, but even adding insulation to a newer home can pay for itself within a few years.