The Issue of the Daylighting Intensity by Light Guides

摘要

The issue of the efficiency of use and determination of the operational efficiency of the designed light sources is relevant during the process of lighting design.The contribution deals with the illumination of the interior by the tubular light guides during design and operation itself.The measurement of the luminance,the illumination of the exterior and the interior was carried out on experimental wooden building in Bmo belonging to VUT FAST(Czech Republic).In one case,the brightness of the sky was also measured.The assessed tubular light guides Sunizer with the length of tube 2 m and-with the diameter of 320 mm passes through the roof structure and through the ceiling structure into the interior corridor of the wooden building.Prior to the start of the measurement,the measuring sensors were placed in the center of the diffusers of the two measured tubular light guides at the floor level.Another one sensor was placed at the midpoint between the diffusers at the floor level.Subsequently,another sensor was placed on the roof of the building in the exterior.The sensor is placed next to the dome of the light guide so that it is not overshadowed.The sensors were connected to the datalogger and the 5-minute measurement was performed at all four locations simultaneously at time intervals after one minute.The values of the sky brightness always in four directions were determined were determined before the measurement,in the middle of the measurement and at the end of the measurement.The sky type was determined visually for some of the measurements.Finally,the measured data from the luxmeter was stored and the ratios of illumination of the interior and exterior were calculated.Subsequently,the measured data are compared with the simulations obtained from the software Holigilm and Velux Daylight Visualizer.The benchmark is the ratio between indoor and outdoor illumination,the so-called daylight factor.Finally,there is an evaluation,a graph showing the difference between these values and the explanation of the differences of results between the real measured values and the outputs from the simulation programs.