Evaluation of dichroic material for enhancing light pipe natural ventilation and daylighting in an integrated system

Integration of natural ventilation and daylighting in a single installation would make both technologies more attractive. One method for the integrati on is the use of concentric light pipe and ventilation stack. By constructi ng the light pipe using dichroic materials, the infrared part of the solar radiation is allowed to be transmitted to the stack but the visible light i s guided by the light pipe into a room. The heat gain to the interior can b e reduced and the thermal stack effect strengthened. Work presented here in volved the experimental and computational evaluation of dichroic materials for enhancing both natural stack ventilation and daylighting. The transmitt ance of a dichroic light pipe was found to be similar to that of a light pi pe with a 95% specular reflectance. The infra-red radiation transmitted thr ough the dichroic material into a passive stack was found to enhance the na tural ventilation flow by up to 14%. The effect is greater in summer than i n winter, which is highly desirable as there is often a lack of driving for ce for natural stack ventilation in summer. (C) 1999 Elsevier Science Ltd. All rights reserved.