The key building characteristics that affect cooling load calculation include construction materials, material properties (U-values, R-values, shading coefficients, solar heat gain coefficients), size, color, shape, location, orientation, external and internal shading, and occupancy type and time of day. These factors influence the amount of heat gain and loss through the building envelope, which in turn affects the cooling load. For example, a building with large windows and south-facing orientation will have a higher cooling load due to increased solar heat gain.