Calculating indoor natural illuminance in overcast sky conditions

The work shows how natural illuminance values inside buildings depend on the calculation method of the sky luminance distribution implemented in the computer code which, for a room of fixed geometry and characteristics, transforms the outdoor meteorological data into indoor illuminance data. By means of the INLUX calculation code, experimentally validated, 12 different calculation methods of sky luminance distribution were compared, sometimes obtaining strong differences among the calculated values of indoor illuminance. The choice of some methods instead of others depends on the meteorological data available in the place considered. Comparing the calculated illuminances with the experimental values measured inside a scale model (1:5), located outdoors in Osaka (Japan), and exposed to daylight, the best calculation methods, among those considered, of sky luminance under overcast sky conditions were identified.

[1]  Danny H.W. Li,et al.  An analysis of daylighting performance for office buildings in Hong Kong , 2008 .

[2]  F. Kasten,et al.  A new table and approximation formula for the relative optial air mass , 1964 .

[3]  P. R. Tregenza,et al.  Subdivision of the sky hemisphere for luminance measurements , 1987 .

[4]  Danny H.W. Li,et al.  Evaluation of overcast-sky luminance models against measured Hong Kong data , 2001 .

[5]  Y. Koga,et al.  Models of sky radiance distribution and sky luminance distribution , 2004 .

[6]  K. K. Gopinathan,et al.  A study on zenith luminance on Madrid overcast skies , 2001 .

[7]  Stephen Wittkopf,et al.  Analysing sky luminance scans and predicting frequent sky patterns in Singapore , 2007 .

[8]  Serm Janjai,et al.  Estimation of sky luminance in the tropics using artificial neural networks: Modeling and performance comparison with the CIE model , 2011 .

[9]  Chris C.S. Lau,et al.  Overcast sky conditions and luminance distribution in Hong Kong , 2004 .

[10]  J. Michalsky,et al.  Modeling daylight availability and irradiance components from direct and global irradiance , 1990 .

[11]  Surapong Chirarattananon,et al.  Distributions of sky luminance and radiance of North Bangkok under standard distributions , 2007 .

[12]  M. B. Kobav,et al.  Simulating and calculating sky luminance distribution with CIE standard DS 011.2 , 2003, The IEEE Region 8 EUROCON 2003. Computer as a Tool..

[13]  Vittorio Ferraro,et al.  Simplified correlations of global, direct and diffuse luminous efficacy on horizontal and vertical surfaces , 2008 .

[14]  Vittorio Ferraro,et al.  INLUX: A calculation code for daylight illuminance predictions inside buildings and its experimental validation , 2009 .

[15]  J. Michalsky,et al.  All-weather model for sky luminance distribution—Preliminary configuration and validation , 1993 .

[16]  Danny H.W. Li,et al.  A simplified procedure for determining indoor daylight illuminance using daylight coefficient concept , 2006 .