House plans with sun tunnels invite natural light into windowless rooms like closets, pantries, and dark hallways. Sun tunnels, also known as sun tubes or light pipes, allow sunlight to stream into areas that normally are not reached by the home's windows. A sun tunnel is a type of skylight that channels light from the roof through a reflective tube and into the room below. The reflective tube ensures that as much light as possible makes it into the home, and the design does not take up much space on the roof or ceiling.