Vertical Illuminance Measurement for Clear Skies in Tehran

To effectively design daylight in buildings, daylight availability data are necessaryalthough there is a great potential for daylight energy in iran, its use has been hampered by the absenceof measured data. in this paper the illuminance data on the vertical south facing surfaces of tehran wereestimated using the iesna model. for this propose an illuminance measuring set was used in order tomeasure the vertical illuminance for standard times over 17 days at one minute intervals from 9 a.m. to 4p.m. then, the measured data were compared with the iesna model calculated data. a regression modelbetween measured and calculated data was developed, which showed an acceptable linear correlation(r2=0.9535). also mean hourly and monthly vertical illuminance was obtained from the new equationbetween measured and calculated data for a whole working year. to estimate daylight availability, iso-klx lines for working hours and frequency curves for vertical illuminance on south facing surfaces wereproduced.