Analysis of vertical light tubes, and diffuser as daylighting system in buildings is presented. The solar light energy is directly addressed to the chosen area of the building with a light tube and diffuser guiding structure. This work highlights illuminance obtained by light tubes in a three storied office building. Field investigation with a scaled prototype and simulations with HOLIGILM, and DIALux are analyzed. It is observed that light tubes can offer large savings in electricity usage by using natural daylight.