R-Value
The effectiveness of insulation is measured by R-value, which indicates how well the insulation will resist heat transfer. Insulation with higher R-values are the most efficient and effective. Determining which R-value is right for your vaulted ceiling depends on the climate where you live, your lifestyle and the type of heating system you have in place.
Types
Rigid foam board insulation comes in panels that can be installed into 2x10 framing. These panels provide resistance to heat transfer through the wooden rafters of your ceiling. When installing rigid foam board insulation, the United States Department of Energy recommends choosing a product that has an R-value of 3.8 to 4.4 per inch of thickness. Blanket insulation comes in batts and rolls, which can be placed into 2x10 framing of your vaulted ceiling. High-density batts in R-30 or R-25 are recommended for vaulted ceilings.
Installation
Insulation must be installed into 2x10 framing in a manner that leaves room for proper ventilation. According to the United States Department of Energy, a vent baffle must be installed between the roof decking and the insulation. Failure to leave room for ventilation or failing to install the proper baffles will result in hot outdoor air coming in and out of your home, which increases energy usage. If the framing in your vaulted ceiling does not allow room for insulation and ventilation, attach strips to the rafters to hold insulation in place.
Considerations
If you install rigid foam board insulation, building codes require it to be covered with a fire-rated product or material. In most areas, drywall is sufficient for this purpose. Blanket insulation does not have to be covered. Once your insulation is placed in your vaulted ceiling, inspect your home for other areas where additional insulation could increase the energy efficiency of your home. Attics and basements are two areas that may benefit from installation of additional insulation.