Rule of Thumb for Daylighting of Rooms with External Obstructions

Abstract

A daylighting rule of thumb or simplified formula for side-lit room with external obstruction has been presented by Littlefair. Based on Littlefair's formula and daylighting simulations generated by AGi-32, a modified rule of thumb for daylighting is proposed for a location in Sydney, New South Wales (Latitude −35° South and Longitude −150° East). Previous daylighting rules of thumb for Sydney based upon simulations using Lumen Micro 8 are revisited and revised. Lumen Micro 8 has been noted for its tendency of giving higher illuminance readings compared to other simulation software. In this research, AGi-32 is utilized in daylighting simulation of medium to large size rooms with external obstructions angles ranging from 5° to 80° from the window sill height (or work plane). The impacts of different surface reflectances (0% and 25%) of external obstructions on indoor illuminance are also examined.