A dramatic cathedral ceiling makes a strong statement in a home's interior, but make sure to follow the best practices to eliminate mold and wood rot while also saving money on lumber and materials. For example spray foam insulation helps create an air-tight seal that eliminates the need for ridge and soffit venting. This also allows you to save on lumber by using 2"x10" framing instead of the traditional 2"x12" boards that were needed for ventilation.