This paper presents a daylighting experimental analysis of a novel vertical light-pipe which incorporates side apertures serving multiple levels to a deep-plan building. A light-pipe system that serves three floors has been developed in which the ground floor is illuminated via a light-pipe by a conventional ceiling mounted diffuser while the first and second floors are lit with daylight outlets on the sidewalls. Illuminance at each level of the three storey building relative to a work plane height, as well as the distance from the luminance source have been determined. The relationship between illuminance level on the work plane and the aperture area for different vertical apertures has been found and the results are presented. To determine the ratio of aperture opening area, A(o), to the work plane height, H-wp, that produces the same illuminance at representative points on a desk at each level, a 1:13 scale model was built to avoid sensor sensitivity problems. A 75 mm-diameter tubing was used to construct a scaled-model designed to emulate the largest 1000 mm-diameter light pipe available, yielding the largest aspect ratio, and thus light transmission at a scale of 1:13. Experiments with outdoor illuminance levels of 11,000 and 14,000 lux gave illuminance at specified reference points of 532 and 80 lux respectively. Importantly, the methodology used in this research can be adopted by architects and building engineers when developing case-specific designs or redevelopment of existing buildings. (C) 2015 Elsevier Ltd. All rights reserved.