Thermal performance prediction of shaded sunken courtyard buildings in a hot arid climate

Abstract

Extensive studies in the literature have shown that earth sheltering is an effective energy conservation strategy for buildings in cold regions; however, its potential in reducing the heat gains in buildings located in hot-dry regions has not been thoroughly investigated. The purpose of this study is to quantify the potential of the shaded sunken courtyard concept as an energy conservation strategy in hot desert regions, and the effect of integrating other passive strategies such as insulation, soil shading, and evaporation (vegetation and irrigation) to maximize the thermal benefits of the sunken courtyard concept. The soil and climate conditions of Kuwait are used as a case study. The thermal performances of a wide range of shaded sunken courtyard configurations are analyzed based on the following design parameters: (1) courtyard geometry, (2) thickness of the soil cover over the roof, (3) insulation, (4) shading of the courtyard and/or the soil surface over an extended building footprint, (5) evapotranspiration at the ground surface, and (6) soil's thermal properties. This investigation is based on a thermal simulation computer program developed herein in FORTRAN to calculate heat flow rates through the sunken building envelope on an hourly basis. The program CONDUCT is used to solve the two-dimensional, partial-differential, heat-conduction equation assumed in the design problem through the fully-implicit finite-difference technique. The results show that, in skin-load-dominated-buildings, the shaded sunken courtyard concept could reduce the energy consumption by 23% in one-story buildings, 28% in multi-story buildings, and up to 35% with the application of other thermal modification strategies when compared to aboveground shaded insulated buildings of equivalent sizes. In larger scale buildings, the effectiveness of the sunken courtyard concept varies from 31% in skin-load-dominated buildings (with 2 W/ft2 of lights and equipment) to only 11% in internal-load-dominated buildings (with 6 W/ft2 of lights and equipment). Design guidelines and rules-of-thumb are suggested, and a series of charts are provided as tools to help designers quickly predict the thermal performance of any shaded sunken courtyard configurations (excluding internal loads) that fall within the selected ranges.