抄録
In lighting design, especially combined design of artificial and natural lighting, standard sky luminance for lighting design must be established. For this purpose, horizontal plain illuminance from 1/4 north sky was measured by automatic recorder continuously for two years from December 1970 to November 1972, in Suita City near Osaka. At the same time, sunshine record was taken using Jordan sunshine recorder to classify the sky condition. The data were investigated and analyzed from the points of solar altitude and sky condition, and the solar altitude-sky illuminance charts are obtained for classified sky conditions respectively. The standard sky illuminance for lighting design must be established on the base of cumulative occurrence rate irrespective of the two factors above mentioned. In this case, the time from 10 to 10 solar altitude was considered as daytime, and the relationship between sky illuminance and cumulative occurrence rate was taken using the whole two years data. From this chart, when 90% range is adoped, the lower and upper value for sky illuminance are 5000 and 50000lx respectively. This upper value is considered some-what two sever, the authors propose the upper value of 80% range, 32000lx, namely 10000cd/m^2 as the actual design value for upper value.
