Comparison of Attic Radiant Barrier Sheet or Sprayed

Basics

• A sheet barrier is usually made of aluminum foil with the shiny side used to reflect heat. Spray barrier is a kind of paint containing metal flecks to reflect heat.

Installation

• You tack a sheet barrier onto the rafters or roll it out on the floor of your attic. You can also apply a sheet barrier on the bottom of your roof or underneath the shingles when you build your roof. Spray barriers are far easier to apply than sheet barriers, and you can apply a spray barrier on everything including attic floor joists.

Efficiency

• The ability of a sheet or spray barrier to reflect heat is called emittance. Shiny materials will usually have a lower emittance number than dark materials. Check your product label for an emittance of less than .25 as measured by the American Society of Testing and Materials. The lower the emittance rating of your radiant barrier, the more you will save. A sheet barrier is about 35 percent more efficient than a spray barrier, but you can more effectively cover all surfaces with spray barriers.

Potential Saving

• You save more if you have ducts to vent hot air that collects in your attic. Ceilings heated by hot air accumulated in an attic are typically responsible for 15 to 25 percent of summer-time cooling costs. A radiant barrier in an attic insulated with R-11 or less can save from 2 to 10 percent in cooling bills. You can reduce ceiling heat from 16 to 42 percent in the summer with a radiant barrier and R-19 insulation in your attic. The Oak Ridge National Laboratory estimates that you can save up to $150 a year in 2008 dollars in energy costs if you use a radiant barrier in Miami and $40 in Baltimore. If you do not have ducts to vent hot air in your attic, the savings drop to $20 in Miami and $5 in Baltimore.