Insulation saves a homeowner money by keeping warm air in a home, similar to a person wearing a jacket to keep warm. Properly installed insulation will slow down the heat transfer from the home during cold periods. During the cooling season, insulation slows down outdoor heat from transferring into homes.
While all materials have some insulating properties, "insulation" generally refers to a material with a high resistance to heat flow.
Common insulation products include glass fiber, cellulose, polystyrene and urethane - to name a few. To reduce the flow of heat these insulation products are are placed in walls, foundations and roofs/attics.
To determine the effectiveness of insulation, products are rated by their "R-value". R-value is a term that places a value on a material's resistance to heat flow. The higher the number per inch, the better the material is at insulating. Since homeowners pay to create heat in their homes using equipment like a furnace, wood stove, a heat pump, etc., the longer the heat stays in a home, the less money a homeowner will pay in heating costs.
The U.S. Department of Energy web site has more information on R-Value of Insulation Materials
