Vaulted ceilings are sometimes called sloped ceilings.
Vaulted ceilings are also known as cathedral ceilings. They are open ceilings that rise to an apex in the roof of the house. They are deployed in preference to the installation of a flat ceiling. However, the presence of a vaulted ceiling typically means that the house lacks an attic, the area most commonly insulated to prevent heat loss from the home, or the entry of exterior heat. As such, the vaulted ceiling must itself be well insulated. There are several types of insulation that can be used.
R-Value
The effectiveness of a material as an insulator is measured by its R-value. This unit is arrived at by dividing a material's thermal conductivity by its depth. The higher the result, the better a material is at preventing heat from passing through it.
Batts
Batt insulation is the use of precut strips of woven material. Also referred to as blankets, these batts are installed between the ceiling and the roof deck. The most common form of batts are fiberglass, a polymer mixture of glass and plastic fibers. They come in a variety of densities, with an average R-value of 3.14 to 4.3 per inch, dependent upon the density of the blanket. Batts also are fabricated from mineral wool, a byproduct of smelting, which averages 3.14 to 4.0 per inch. Plastic fiber batts, typically manufactured from recycled plastic beverage containers, have an average R-value of 3.8 to 4.3.
Sprayed Foam
A second option is the installation of sprayed foam into the space between the ceiling and the roof deck. Manufactured from polyurethane, the foam comes in a liquid form that is sprayed into the cavity with a pressurized-air machine. The foam hardens and expands to fill the space, conforming to its contours and so minimizing air voids in the insulation. This makes for an effective barrier to heat and moisture, with an average R-value of 6.25 per inch. Installation usually is performed by a professional, and a fire-resistant covering must be added to the ceiling if using sprayed foam.
Foam Boards
Rigid foam boards are another option for insulating a vaulted ceiling. These are affixed to the underside of the rafters and are particularly useful if there is limited space available between the ceiling and the roof deck. Rigid boards most commonly are manufactured from polystyrene, which has an average R-value of 4.0 to 5.0 per inch. They can also be fabricated from polyurethane, with an R-value of 6.25. Rigid foam boards sometimes come with a radiant barrier as a facing. These barriers, usually made from metal foil, add an extra 2 per inch to the board's R-value.
Tags: average R-value, average R-value inch, between ceiling, , ceiling roof, ceiling roof deck