Iran's traditional architecture has been admired by architects regarding its aesthetic values and wise architectural and structural solutions, but very rarely is it discussed why this architecture is not used any longer, or how it can be adapted to contemporary living and architecture standards, specifically in contribution to its environmental considerations. In recent decades, energy crisis, depletion of natural resources and environment pollution have been challenging issues especially in fossil-fuel dependent countries like Iran and more specifically in hot and arid regions with a challenging climate. At present one important trend in response to these emerging problems is to assist architects and designers by providing them guidelines for a more sustainable approach in architectural design specifically developing countries of Iran, where sustainability is a new debate and normally misused or misunderstood with very high-tech architectures or smart buildings that require high grey energy to be constructed and advanced technologies to operate. In Iran, with thousands of years of architectural background and a huge legacy of traditional architecture, while the traditional architects did not have access to high technological solutions, they tried to find very simple but efficient local low-tech solutions for a more environment-friendly architecture to deal with the sever climatic conditions of hot and arid desert area. These solutions were used, upgraded and passed from one generation to the next till the reformations of the 20th century in Iran, while different reasons caused these simple sustainable solutions in Iran-s traditional architecture to become abandoned. This resulted in a contemporary architecture that follows global style all over the country, regardless of huge climatic and contextual differences in the country that covers a wide range of climates including cold mountains in the west, moderate climate of the Caspian sea area in North, very hot and humid gulf side areas in the South near the Persian Gulf as well as the very extensive area of hot and humid central deserts. This dissertation focuses on the lessons and inspirations from sustainable Iranian traditional housing solutions in hot and arid region, and assess them according to modern architectural design criteria to see which solutions can be used again, which ones must be changed and which ones cannot be utilized any longer. By implementation of empirical research, four successive phases are defined for the project: - Selection of comprehensive case studies - Defining the relevant evaluation system, - Evaluation of case studies in terms of environmental sustainability - Conclusion and recommendations 7 The research is fulfilled by using mixed (qualitative and quantitative) method through an inductive approach. For the beginning, this project starts to discuss if traditional architecture in Iran was sustainable or not. In order to get to a more accurate discussion, contemporary architecture is also evaluated. Therefore case studies from among both traditional as well as contemporary types of housings are selected. In order to avoid subjective evaluation and to do the evaluation in a more scientific way, the major challenge is to find the right baseline for evaluation of sustainability in the selected case studies. Since Iran does not yet have any sustainability evaluation system for buildings, the probable choice is to select among the existing evaluation systems worldwide. This research first discusses the practical solutions to evaluate sustainability in houses, and then goes through a brief review of the existing national and international evaluation systems in the world, and the sub-categories they use for evaluation, all of which share lots of similarities and all claim to have the capacity to be used internationally. According to the climatic similarities between Iran and the US, the author finally selected LEED evaluation system as one of the oldest, simplest and most user-friendly and widely internationally used evaluation systems. Nevertheless due to the limitations of using an evaluation system for both traditional and contemporary housings in their very different contexts, and due to the emphasis in existing evaluation systems such as LEED that encourage the users to use specific housing equipment or appliances for achievement of higher credits, this dissertation draws a proper evaluation system that works parallel with LEED in a critical viewpoint in order to define solutions that are adaptable at the architectural design stage. The evaluation topics defined finally, focus on five major features of architectural sustainability including: - Water - Energy - Ground and Land Use - Material - Health and Wellbeing. In each category, contemporary and traditional case studies are investigated and evaluated to find out which is more sustainable; the traditional or contemporary housing and to learn the sustainable strategies adapted in each group.