This addendum changes the daylighting definitions to coincide with those in ASHRAE/IESNA Standard 90.1 to facilitate consistent use of these terms. Some changes are semantic, such as changing from daylight zone to daylight area and changing from adjacent to vertical fenestration to primary sidelight area. For the daylight area under skylights and under roof monitors, geometric relationships between obstructions, heights, and distances from glazing are provided to allow daylight areas to extend beyond obstructions where appropriate. Clerestory was deleted since roof monitor sufficiently describes roof elements other than skylights. The changes to toplighting are not substantive but are proposed to utilize the same text as ASHRAE/IESNA Standard 90.1 to ensure consistent use. Effective aperture has been replaced with sidelighting effective aperture, again to coincide with ASHRAE/IESNA Standard 90.1. For background documentation on the analysis used to derive sidelighting effective aperture, refer to www.h-m-g.com/ASHRAE_Daylighting.