ABSTRACT
Most new developments on a site will have some sky obstructed by existing buildings, topography or vegetation. Any obstructed sky, particularly for cloudy climates, represents a potentially signifi cant loss of daylight available to a building. It is, therefore, important to have a good awareness of the obstructions on the site and the sky blockage they will create at locations on the façades of the new buildings. To check if good daylighting on an obstructed site is possible, a simple assessment can be made by drawing a section of the new building and an existing obstruction. Draw a line from a point 2m above ground level on the new building to the top of the obstruction and measure the angle between the line and the horizontal, as shown in Figure 16.1. If this angle is less than the critical obstruction angle h given in Table 16.1 for various latitudes then there is potential for adequate daylighting of the new building.
