N latitude For south-facing windows, the shading geometries provide guidance for the appropriate dimensions of roof overhangs. However, situations may require a different geometry, depending on the balance between heating and cooling loads for the particular building and factors such as required window sizes and building practices. Additional shading strategies such as vertical louvers may be needed. The tables containing average climatic condition information list monthly and yearly values for the following parameters. Average clearness index, Kt.
Degree days indicate heating and cooling requirements of buildings.
They are defined as the difference between the average temperature for the day and a base temperature. If the average is greater than the base value, the difference is designated as cooling degree days. Because clouds decrease the amount of solar radiation reaching the earth, stations in cloudy regions will have lower values for Kt than stations in regions will fewer clouds. For example, data for 3 p.m. include the illuminance received from 2 p.m. to 3 p.m. The hours for March and December are local standard time. The hours for June and September are either local standard time or daylight saving time, depending on whether the staion observes daylight saving time.