The Rolls of Insulation for the Walls of a Room calculator computes the number of rolls or batts 
of insulation needed for the WALLS of a room based on the length and height of the four walls. The calculator assumes standard 16" spacing on the studs.
INSTRUCTIONS: Choose units and enter the following:
- (L) Length of Room
- (W) Width of Room
- (H) Height of Room
- (RL) Insulation Roll Length
- (RW) Insulation Roll Width (16" in diagram)
Insulation Rolls for a Room (nR): The calculator returns number of rolls or batts of insulation (rounded up) and the total linear feet of insulation.
The Math/Science
INSULATION (THERMAL) is a material used to inhibit heat transfer. More simply, insulation
keeps-in heat when it's cold outside, or keeps-out heat when it's hot outside. It's used in buildings, vehicles and boats. It's used in roofs, walls, floors and around pipes to keep them from freezing or losing heat in hot water. Insulation is a value contributor with good return on investment by lowering heating and cooling costs. It is also an environmental plus by reducing the energy needed to maintain comfortable temperatures where humans and animals spend time.
Thermal insulation used in construction comes in several shapes and products. The most common form is rolls of fiberglass known as batting. These rolls are rolled out and placed between studs in exterior walls, between rafters and trusses in attics with no floor, or between joists in attics or on first floors where the underside is exposed to the outside (e.g., crawl spaces). 
Another common form of insulation is blow-in or sprayed-in material that conforms to the area applied. The common products include cellulose, which is treated paper, shredded polystyrene, loose fiberglass and denim. Styrofoam panels are another common insulating material.
Batts (batting sheets) are sections of insulation attached to paper or foil that allows them to be laid between joist or rafters in a way where the paper or foil is used to fix the batt to rafter. Rolls of insulation (e.g., fiberglass) also will be attached to liner medium (paper or foil) and can be cut into length (batts) by the installer.
Loose insulation is best applied with an insulation blower. Loose insulation, such as cellulose, is normally treated for flame resistance, while fiberglass is naturally flame resistant. 
Blown-in insulation typically comes compressed in bags. These require the material to be appropriately expanded for optimum benefit. For cellulose and fiberglass, this expansion is easily done using an insulation blower with a 100 foot hose. Because, power is not always available or the use of a blower inconvenient, raked insulation is also available.
The effectiveness of thermal insulation increases by the thickness of the layer of insulation. The following table shows the per inch increase in R Value of different materials.
