Reasons To Insulate

• Generally, insulation deployed on the walls and rim joints of basements tends to be a more effective way to prevent heat loss. However, this is not always possible. Insulating the basement ceiling, however, can help lower your energy bills, serving as under-floor heating for the room above the basement by helping to contain heat in that room. Basement ceilings typically house a lot of electrical wiring, pipes and duct work, and access to them may determine the type of material used.
  
  

Effectiveness

• The effectiveness of insulation materials is rated on a scale known as an R-value. This reflects the material’s ability to prevent heat from flowing through it. The value is calculated by dividing the thickness of the material by its thermal conductivity. The higher the R-value, the more effective the insulation.
  
  

Glass Fiber Batts

• The most common way to insulate a basement ceiling is to affix glass fiber batts to it. Batts are lengths of material that come either pre-cut or on a roll for you to cut required lengths from. Glass fiber has an R-value that averages 3.2, and is naturally fire-resistant. You should first affix a vapor-proof sheet to the ceiling before installing the batts to help prevent mold and mildew from forming. Pipes and heat ducts should also be insulated if you use glass fiber batts.
  
  

Blown-In Polyurethane Foam

• Polyurethane foam comes as a liquid that is blown onto the basement ceiling using pressurized air. You can rent spraying machines or employ specialized workers to perform the installation. Protective clothing and a face mask must be worn during installation. The foam is sprayed onto a thickness of about 2 inches and hardens within seconds, resulting in a moisture- and air-resistant barrier. It has among the highest R-values of any insulation material, averaging 6 per inch. Polyurethane foam typically must be covered with a fire-resistant material to comply with many local building codes.
  
  

Foam Boards

• Foam boards may be made from polyurethane or polystyrene, and are backed and faced with metal or foil. The former has an average R-value of between 5.8 and 7.2 per inch, while the latter averages between 3.7 and 5. Foam boards must be covered by a fire-resistant material after installation. The efficacy of foam boards depends on correct installation – minimizing air and vapor entry points – and so should be performed by a qualified professional.