Methods for the illumination of multilevel buildings with vertical light pipes

• We examine the feasibility of using mirrored light pipes in multi-level buildings.
• We propose a method to extract equal amounts of light at each level.
• We test new daylight collectors, using laser cut panels to improve effectiveness of light pipes.
• We formulate the theory to estimate performance of light pipes in multi-level buildings.
• We found that tracked collector increased illuminance at lower levels by a factor of 7.

This paper examines the feasibility of using vertical light pipes to naturally illuminate the central core of a multilevel building not reached by window light. The challenges addressed were finding a method to extract and distribute equal amounts of light at each level and designing collectors to improve the effectiveness of vertical light pipes in delivering low elevation sunlight to the interior. Extraction was achieved by inserting partially reflecting cones within transparent sections of the pipes at each floor level. Theory was formulated to estimate the partial reflectance necessary to provide equal light extraction at each level. Designs for daylight collectors formed from laser cut panels tilted above the light pipe were developed and the benefits and limitations of static collectors as opposed to collectors that follow the sun azimuth investigated. Performance was assessed with both basic and detailed mathematical simulation and by observations made with a five level model building under clear sky conditions.