On the average horizontal illuminance in rooms with one or two point light sources

Abstract

ABSTRACT To ensure high-quality lighting in indoor spaces, many objective parameters have been suggested in building codes and standards all over the world. Despite the emergence of luminance-based metrics, the average horizontal illuminance (E av) remains popular in practice. For the case of relatively small rooms with one or two point light sources, it is often intended to determine the point with horizontal illuminance equal to E av. It is also intended to have the computation for various room scenarios, so that the outcome can be predicted using a simple model. This study, therefore, aims to propose a method to identify the location of point of E av on horizontal plane in cuboid rooms with various sizes, with one or two point light sources, and to further verify the theoretical concept. To achieve the objective, scenarios and assumptions are described using mathematical tools, followed with verification using grid computations and Monte Carlo simulation of 10,000 random scenarios. Logarithmic models to predict E av value and its representative location are proposed. The room length-to-width ratio is found more influential, compared to the source luminous intensity characteristics, in affecting the location of point of E av.