On the Assignment of Target/Ambient Illuminance Ratio in Designing Mean Room Surface Exitance

Abstract

ABSTRACT In the application of lighting design objectives (LiDOs) procedure, the target first reflected flux (FRF) may at times underestimate or overestimate the expected FRF based on the specified mean room surface exitance (MRSE). In that case, further manipulation of the direct illumination is required. To avoid such remedial actions, the appropriate target/ambient illuminance ratio (TAIR) for each room surface shall be assigned. This article aims to propose methods to optimally assign the TAIR values, demonstrated through analytical calculation and worked examples. In the recommended scenario, the designers are given the freedom to choose the desired TAIR for each surface, except for the last (n-th) surface, which must be computed individually to guarantee that the specified MRSE is achieved in the actual result. An optimization approach to minimize the energy associated with the total direct flux is also proposed using Monte Carlo simulation technique, which can be done using a simple calculation spreadsheet, in which the lower and upper boundaries for each TAIR value are introduced as input. Overall, this article has contributed to giving better insight on the MRSE design calculations, while helping lighting designers to satisfy the target appearance, without losing too much flexibility.