The geometry of the urban consists of solid and void, buildings and streets. Proper street orientation and layout of homes can have considerable effect on the shading, which affects the urban micro-climate. The street geometry as defined by height/width ratio, sky view factor and the orientation which is defined by its long axis, can influence the absorption and emission of incoming solar and outgoing long and short wave radiations which, has a significant impact on the temperature variations within the street canyon.

The objective of this research is to evaluate and to compare mutually the microclimate variation of urban street canyon according to its geometry: size (Sky view factor) and orientation in down town of Constantine-Algeria (semi arid climate) and to see how both factors affect the thermal comfort level in the street. The methodology is based on numerical modeling by means of the 3D model Envi-met. In general, the results show that there are less air temperature variations but demonstrate that a number of useful relationships exist between the geometry and the microclimate.