Work out sky view factor instantly with clear inputs, formula shown and shareable results.
Sky view factor is the fraction of the hemisphere visible from a point, and for the centre of an infinitely long street canyon it equals the cosine of the angle from vertical to the building parapet. A low factor means less daylight during the day and, more importantly, less radiative cooling at night, which is the mechanism behind the urban heat island.
Sky view factor
SVF = cos(arctan(H / (W/2))) at the centre of a street canyon
Aspect ratio
H/W, the height to width ratio of the canyon
SVF = cos(arctan(H / (W/2))) at the centre of a street canyon. Sky view factor is the fraction of the hemisphere visible from a point, and for the centre of an infinitely long street canyon it equals the cosine of the angle from vertical to the building parapet.
Because surfaces cool by radiating to the cold sky. When buildings block most of the hemisphere, that heat is radiated to other warm surfaces instead and the street stays hot after dark.
This calculator takes 2 inputs: Street width between building faces, Building height. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.