What type of insulation will make your home most energy efficient?

The U.S. Department of Energy estimates that 50 percent to 70 percent of the energy used in a home is consumed by heating and cooling. You can significantly improve your home's energy efficiency and lower your energy bills by making sure your home is properly insulated. Experts say your home's walls and attic, as well as floors above unheated garages, crawl spaces and unfinished basements should all be insulated.

There are four main types of home insulation: blanket insulation, which is packaged as rolls or precut sections called batts; loose-fill insulation; rigid foam board insulation; and spray foam insulation. Fiberglass, thermoplastic foam (including polyurethane, polystyrene and polyisocyanurate), cellulose and (to a lesser extent) mineral wool are the most common insulation materials. Some insulation types, such as fiberglass or loose foam, will also require a vapor barrier to protect the material from moisture damage that can accumulate over time.

Experts say choosing the best insulation depends on your climate, the location in your home where the insulation will be installed, whether you have a new or existing house, and how much you want to spend (assuming you end up with more than one viable option). 

Types of Home Insulation

Loose-fill Insulation *Est. $0.01 to $0.02 per square foot per R-value
Advantages
  • Suitable for unfinished (open) or finished (enclosed) walls
  • Good choice for attics
Disadvantages
  • Can settle, reducing efficiency
  • Installation best left to pros
  • May require a vapor barrier
Loose-fill insulation, also called blown-in insulation, is typically composed of fiberglass, cellulose (recycled paper) or mineral wool; recycled cotton also can be used, though it is less common. Loose-fill insulation is blown into a space, usually with a pneumatic blower through a hole drilled into the wall. Though usually installed dry, it can also be blown in damp to prevent air gaps and keep it from settling.
Blanket Insulation *Est. $0.02 to $0.03 per square foot per R-value
Advantages
  • Suitable for DIY projects
  • Ideal for attics, unfinished (open) walls
Disadvantages
  • Can't install in finished (enclosed) walls
  • Requires care when installing around fixtures, obstructions
Blanket insulation comes in sheets and is usually made of fiberglass, but sometimes it is made of mineral wool, cotton or another natural fiber. You can buy it with a foil or kraft paper facing that acts as a vapor barrier to protect against moisture. Proper installation is required to prevent air gaps or compression, which can reduce the insulation's R-value, but DIY installation is possible. Blanket insulation is only suitable for unfinished walls.
Rigid Foam Board Insulation *Est. $0.07 to $0.10 per square foot per R-value
Advantages
  • Most insulating type
  • Suitable for insulating basement interior walls
  • Suitable for insulating exterior walls on new construction
  • Can be installed by pros or homeowners
Disadvantages
  • Not for finished (enclosed) walls
  • Expensive
  • May release toxic gases if burned
Rigid foam board insulation used in residential buildings is made from petroleum-derived products, usually polystyrene and polyisocyanurate (also called polyiso). Although not readily prone to combustion, this type of insulation could release toxic gases during a fire, so it must be protected with a layer of drywall or plaster. Rigid foam board insulation is used in walls, floors, ceilings and foundations, primarily in new homes or major renovations. The advantage is that it's extremely efficient.
Spray Foam Insulation *Est. $0.07 to $0.15 per square foot per R-value
Advantages
  • Suitable for unfinished (open) or finished (enclosed) walls
  • Conforms to any space, large or small
Disadvantages
  • Expensive
  • Must be installed by professionals
  • May release toxic gases if burned
Spray foam insulation is typically made from either high- or low-density polyurethane. Many hardware stores sell foam insulation in spray cans to seal cracks around doors, windows and vents, but larger applications require professional installation. It can be used in existing walls by blowing it in through small holes that are then filled. It is also used in attics.
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