A base case model is a more potent dose for applied research; the passive architectural design for sustainability requires optimised experiments. However, experimenting with physical developments require construction and deconstruction until they achieved the optimal scenario. These wastes resources and time; hence, base models' development as useful instruments in the optimisation design process is desirable. Lecture theatres in universities have no specific design model whereby optimising one may not apply to the other. Therefore, this research evaluated a base model for lecture theatre regarding spatial configuration, daylighting potentials, and optimised window-to-wall ratio (WWR) for tropical daylighting. A study of ten existing lecture theatres in eight universities within eight states in Nigeria's hot-humid climate was analysed descriptively for the base model. The study employed Simulations with IES-VE software. The daylighting performance analysis adopted the daylighting rule of thumb, daylight factor, work plane illuminance (WPI), and WPI ratio. The results show that a typical lecture theatre in the study area has a dimensional configuration of 12×20 m floor plan, 6 m ceiling height, and a window wall ratio (WWR) of 13%. In the deduced base model, 4H was required for adequate daylighting against the thumb's 2.5 H daylighting rule. The research concludes a low window-wall ratio with poor daylighting quality and quantities in the base model; therefore, it implies that the daylighting was not a criterion in the designs. However, the experiment revealed a progression in daylighting performance with an increase in WWR from the base case until 30% WWR. Beyond that, there was a decline in the daylighting performance. Therefore, 30% WWR was optimal for daylighting performance in lecture theatre retrofitting within the tropical climate
