External Shading for Passive Thermal and Daylighting Design a Case of Small Learning Spaces in Tropic Upland Climate of Nairobi

Abstract

In a tropic climate, cooling dominates the highest energy consumption for buildings (UN-Habitat, 2014). Approximately 50% of these cooling loads occur through the building envelope, mainly due to the building form and architectural shading devices. Buildings in Nairobi have not survived the vice either, despite the fact that the climate of Nairobi presents an opportunity for passive design (Kimeu, 2014). With good design, there is no need for either heating or cooling in buildings. Despite this advantage, the demand for thermal cooling and visual comfort remains an important issue in learning spaces in the City of Nairobi. Most buildings are marked as high-spenders on artificial lighting and thermal cooling (Moraa, 2019). This phenomenon is directly related to the design of the building envelope, in which external architectural shading elements fall. This study, therefore, explored and presented an external shading device as a contributor to the indoor thermal and lighting environment. The study aimed to find an optimal trade-off between visual comfort and thermal comfort using a shading device. The study adopted a case study approach and computer simulation to explore the performance of vertical, horizontal, and egg-crate types of external shading devices for thermal control and daylighting within small learning spaces. It was established, through literature and actual simulation, that the egg crate is the best performing external shade in the indoor lighting and thermal environment, while vertical shading was the least performing external shade. In addition, the sizing, shape, location and the material of the devices played a significant role in influencing the indoor lighting and thermal environment.