Rainscreen Principle

In Design

A skylight designed per the rain screen principle has an outer and an inner surface separated by an air space that is confined but open to the outside. The “rain screen” is the outer surface, exposed to wind and water. Water penetration is resisted not by trying to seal all the outer surface joints, but rather by equalizing the pressure on the outer and inner surfaces. Airflow is permitted into the confined space and back out to equalize the air pressure and avert wind-driven water penetration. Water allowed into the confined space is channeled and drained to the outside, keeping the inner surface and its air seals dry.

Thus the system has two stages of protection: an outer rain screen designed to minimize and manage water penetration, and an inner surface sealed against air penetration. Neither surface has to be proof against air and water, a difficult prospect.

Every skylight designed per the rain screen principle features these components:

1. An outer barrier against wind and water.

2. A confined air space drained to the outside.

3. A dry interior barrier sealed against air penetration.

A properly designed and fabricated skylight will be structurally sound, withstanding specified wind loads, and leak-proof, preventing the passage of air and water into the living space.