In this research the thermal performance of ready-made garments (RMG) factory building's envelope has been measured on the basis of internationally established indoor thermal comfort range for the workers. A three-dimensional model has been developed to conduct thermal simulations for typical RMG factory. The simulated factory has been divided into three different zones based on their activities and results have been analyzed by means of statistical distributions. Two types of variables were considered in this study, these were 'thickness of the exterior wall' and 'type of the local construction materials'. Nineteen different exterior wall construction types have been observed through simulations. Prior to the simulations, thermal properties of available local materials were measured in the laboratory. From the analysis, it was found that change of building exterior wall materials and their constructions have significant contributions on the indoor thermal environment of RMG factory building particularly in production spaces. It was also observed that in brick constructions using 2nd class local brick's potentially results in higher indoor temperature leading to poor thermal condition. However, the thermal performance of 3rd class local brick constructions has been found relatively better than other types because of porosity and physical properties of the materials used. (C) 2015 Elsevier B.V. All rights reserved.