Vaulted ceilings often have irregular shapes that are difficult to insulate.
The best type of insulation for vaulted ceilings depends on the amount of room between your ceiling and the bottom of the roof. Vaulted ceilings have limited space for insulation, often making it difficult to maintain adequate ventilation using bulky insulation. Vaulted ceilings often require additional vents in the eaves and ridge line of the roof to provide adequate ventilation.
Rigid Foam
Rigid foam insulation is often used in vaulted ceilings without the necessary space for batt insulation. Rigid foam insulation provides a high R-value and requires the least amount of space. This type of insulation is often more flammable than other types of insulation and requires a minimum amount of fireproofing material to ensure a safe installation. In many cases drywall is sufficient, however your local building codes may require a more substantial form of fireproofing.
Loose Fill
Loose-fill insulation is an effective method for insulating vaulted ceilings with a relatively shallow slope. According to the Oregon Department of Energy, vaulted ceilings with a slope exceeding 3/12 should not use loose fill insulation since the insulation tends to shift towards the eaves of the roof. Loose-fill insulation does have several advantages over other types of insulation. You can install it in finished ceilings without removing the drywall, and it is more compact than of insulation with an equivalent R-value.
Batt
High-density fiberglass batts are often used in vaulted ceilings with at least 8 inches of room for insulation. This type of insulation is easier to install than other forms of insulation and often comes with an integrated vapor barrier. If there is less than 10 inches of space between your ceiling and the underside of your roof, batt insulation will prevent proper ventilation of your insulation.
Ventilation
Adequately venting your vaulted ceiling prevents moisture damage to your insulation during the winter and provides additional cooling in the summer. Installing vents in the soffit on the underside of your eaves and along the ridge line of the roof will prevent moisture from damaging your insulation. According to the University of Kentucky, you should allow one square foot of venting for 150 square feet of area on the attic floor.
Vapor Barrier
Vapor barriers are used to prevent moisture from entering your attic. In most cases the vapor barrier consists of a plastic sheet that rests between the ceiling and your insulation. Vaulted ceilings with less than 44 inches of clearance between the insulation and the underside of the roof at its ridge line need a vapor barrier, since their ventilation is restricted.
Tags: ceilings with, insulation often, your insulation, other types,