Abstract：The global concerns about environmental sustainability elevate the aspirations for advanced building thermal analysis. Hong Kong, like many other places did in the 1990s, has introduced the performancebased building energy code, in that simulation tools are allowed for analyzing the thermal processes and energy consumptions in buildings. It has been noted that different popular simulation tools adopt different solar models to predict the solar irradiation on external facades. This paper, with a focus on studying the solar radiation on vertical facades in Hong Kong, gives a brief review of the solar distribution models and compares the numerical results from three different simulation programs. It was found that though all three models predict that the one facing south-west will receive the maximum solar radiation annually, the results indicate that there are discrepancies in predicted radiation level received in other directions. The deviation among the three models reaches almost ±10%.

Keywords: Solar radiation; Building design; Building simulation