Sometimes the insulation around the vertical portions of a skylight will fall off or is never installed, to begin with. This allows outside air to radiate through the drywall and into the living spaces below. This can make a home feel uncomfortable in certain areas. Closed-cell spray foam is installed on all surfaces of the skylight chase with an average thickness of 2 inches. This keeps the outside air away from the drywall and lessens airflow into the living spaces below.