How to insulate a cathedral ceiling: interior vs. exterior

High ceilings, particularly cathedral and vaulted varieties, are beautiful in nearly any home. Unfortunately, they’re notorious for letting warm air escape, which can be a problem during the winter. If you have ceilings like this in your home, insulation is key.

Insulating from the exterior
Applying insulation from the roof is the best way to ensure a tight seal. First, spray a layer of polyurethane foam and then install a moisture-proof membrane to keep it dry. Homes in cooler climates may also require a rigid foam board to increase thermal performance.

Insulating from the interior
Insulating your home from the inside is possible, but it won’t create an air-tight seal. The best way to do it is to apply blown-in cellulose insulation between the roof decking and the drywall ceiling. There are other ways, but these involve completely removing the ceiling.

No matter how you decide to insulate your roof, it’s important to leave enough room for ventilation and be certain that moisture can’t get through.

Insulating a ceiling is a complex job. To ensure it’s done right, consult a professional.