Are light wells suitable for illuminating residential spaces? Normative discussions

Abstract Light wells in residential buildings represent a context that has received relatively little attention in daylighting analyses. This study aims to analyze the daylighting performance of a residential space with a window facing a light well, in order to contribute to the revision of NBR 15575:2013. The study conducted 1,152 daylighting analyses considering windows facing a light well, located on the first and fourth floors of a 4-story building. Clear and intermediate skies were considered in four Brazilian cities with different latitudes. Both the prescriptive method and point-in-time simulations were applied. The effectiveness of achieving daylit interior spaces through light wells strongly depends on the geometry of the light well and the external illuminance conditions of the city. Narrow light wells were found to be unsuitable for adequately daylighting the lower floor spaces. Furthermore, the prescriptive method was insufficient in representing daylighting originating solely from external wall interreflections. The study found that intermediate and superior performance levels, when achieved through point-in-time or spatial daylighting availability simulations, were never attained for the first-floor space. Therefore, the authors recommend that dense urban canyon situations and light wells be carefully considered in the revision of the standard.