Cathedral Ceiling Insulation

It's difficult to insulate a cathedral ceiling. The depth or thickness of the insulation in a cathedral ceiling is limited by the depth of the ceiling rafters.

If there are recessed lights in the ceiling, areas around these lights will interrupt the insulation layer. Holes made for the recessed lights provide pathways for air leakage, allowing conditioned interior air to escape into the ceiling cavity.

Air sealing around recessed lights is recommended

Unless the ceiling space is accessible from above, it can be difficult or impossible to install additional insulation in a cathedral ceiling. But energy performance can be improved by sealing leaks around any recessed light fixtures in the ceiling.

A new cathedral ceiling can be insulated in several ways

In new construction, there are different options for insulating a cathedral ceiling. In all cases, it's wise to limit or eliminate the use of recessed lights in the ceiling. Using surface-mount versions instead will maintain a more continuous insulation layer.

Fiberglass batts can be "friction-fit" between rafters, as long as insulation baffles are installed before placing the batts to maintain roof ventilation. Spray foam insulation can be applied in the space between rafters, although this treatment is controversial because it eliminates the ventilation space that allows the roof to "breathe."

Rigid foam insulation can also be used to insulate rafters in a cathedral ceiling. The foam panels can be cut to fit between rafters, fastened to rafter bottom edges, or both. In all cases, an airspace beneath the roof sheathing should be maintained to promote roof ventilation.

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