Technically, all insulation improves the energy efficiency of a house to some extent, because that is the purpose of insulation. There are different types of insulation, however, and each type has a different R-value. R-value measures how effective the insulation is at resisting the transfer of heat from one area to another. When the R-value is higher, the insulation is more energy efficient.
To understand what energy efficient insulation is, it is helpful to first explain what insulation is. Heat naturally moves from warmer to cooler areas, and insulation is the material used to reduce the amount of that heat flow. Insulation helps to keep a house warmer on a cold day by keeping heat generated by the heating system, like a furnace or wood stove, inside the house longer. Similarly, it helps cool a house on a warm day by keeping the outside heat from coming into the house.
Energy efficient insulation comes in many different forms. Some commonly used types include batt insulation, blown-in loose fill, and rigid foam. Using the right material for each area of the house and properly installing each type is critical to achieving the R-value assigned to each energy efficient insulation type.
Batt insulation is usually made of fiberglass and comes in big rolls with a vapor barrier on one side. This type of insulation is typically unrolled and fitted between wall studs and ceiling joists. The R-value varies with the thickness of the insulation blanket.
Another type of energy efficient insulation is loose fill fiber. This material is often made of fiberglass or cellulose, and is usually blown into hard to reach areas, such as attics, using a high-powered insulation-blowing machine. It is also used to retrofit an existing house with insulation, since it is not cost efficient to tear down walls to install more structured insulation. The R-value varies depending on the type of material the insulation is made of.
Rigid foam insulation comes in formed sheets of fiberglass, polystyrene, or polyurethane. It is used to insulate basement walls, exterior walls, or crawl spaces. Again, the R-value depends on which type of material is used to make this energy efficient insulation.
All insulation is used to promote energy efficiency, but some materials are better than others. The R-value and installation instructions should be followed closely to achieve maximum energy efficiency from any insulation type.