A Comparative Analysis of Thermal Performance, Annual Energy Use, and Life Cycle Costs of Low-cost Houses Made with Mud Bricks and Earthbag Wall Systems in Sub-Saharan Africa

Abstract

Given the high demand for low-cost housing by the low-income earners, coupled with the tropical climate experienced in sub-Saharan Africa, new-built housing stock needs utmost attention to cost, durability, and efficiency. With the walls accounting for a substantial proportion of the total building cost, choice of a wall system for use in building construction is critical. This choice usually depends on how durable, comfortable, ecological, and economical a given system is, to meet both the quality standards and low-cost aspects of housing. Although the earthbag building system allows for the construction of strong, affordable, and sustainable housing, it is not widely known. As such, its sustainable characteristics have gone unrecognised throughout the building industry. This paper examines and compares the thermal properties and total Life Cycle Costs (LCC) of earthbag walls with the commonly used burnt brick walls - based on the Degree-Days method and Life Cycle Costing analyses of building walls located in one of the hottest regions in Uganda. In-situ measurements of temperature and heat flux were conducted in accordance with ISO 9869 and the annual energy requirements obtained. The total LCC were calculated based on the initial construction costs and annual energy costs attributed to the building wall systems. Earthbags housing was found to be thermal-physically better than the brick wall with a lower U-value resulting in lower annual energy requirements and a huge saving in annual energy costs of up to 83.2%. This saving, coupled with low initial construction costs made the earthbag unit 68.7% cheaper than the burnt brick unit over a 30-year period. Therefore, this study findings suggest earthbag walling system as an economically viable and technically feasible low-cost construction option for rural areas and low-incomers earners’ housing in warm climatic conditions, a characteristic of sub-Saharan countries – so as to promote regional development.