Advantages

• As for most insulation, a primary reason for insulating a basement is to save on heating costs. The U.S. Department of Energy suggests that, depending on the area where you live and the type of insulation, insulating a basement can save a household up to $400 a year. Interior basement insulation is also typically less expensive to install than exterior types.
  
  

Disadvantages

• Installing insulation on the basement walls decreases the available area in the basement by several inches. This can be important if the basement is small or is used as a living area. Most insulation on basement walls needs to be used in conjunction with a vapor barrier to prevent moisture buildup, which can degrade the insulation. Interior wall insulation does not protect the building’s waterproof coating as exterior insulation does.
  
  

Batts

• Batts are some of the cheapest forms of insulation that can be used for basement walls. They are precut lengths of woven material that can be trimmed by the installer to fit the required space. They are also used to insulate visible ductwork and piping on the basement walls, which raises the effectiveness of the insulation. Usually insulation batts are made from fiberglass, but they can also be fabricated from rock wool, made from the byproducts of industrial processes such as smelting. Both are naturally fire-resistant and good vapor barriers.
  
  

Foam

• Sprayed foam is a more expensive option but provides better insulation because it is more effective at minimizing air and water passage. The foam, made from polyurethane, is sprayed onto the walls using a pressurized-air machine. It hardens and expands in place. It is particularly good for irregular walls, as it conforms to the contours of the wall. It must be covered with a fire-resistant barrier.
  
  

Boards

• Foam boards are another option. These are rigid lengths of material made from polyurethane, polystyrene or polyisocyanurate that are affixed to the wall. All need to be installed with a vapour barrier; either a separate layer, or as a facing of heavy-duty paper or foil on the boards.
  
  

Loose Fill

• Interior basement walls can also be insulated by other materials that are finely shredded, treated with a coagulant, then sprayed on the walls. They harden and provide a barrier against heat, air and moisture. These materials include cellulose, fiberglass and rock wool.