Manifestations of sustainable design require renewable resources, impact the environment minimally, and connect people with the natural environment. This article is aimed to investigate the concept of Iranian traditional courtyards, as microclimate modifiers, for sustainable building design in hot-arid regions. To this end, a quantitative field survey is conducted to analyze various physicalel ements including the orientation, dimensions and proportions of enclosed and open spaces, physical bodies (opaque walls), and transparent surfaces (openings) as well as natural elements (water and soil) in nine valuable Iranian traditional courtyard houses from BWhs mesoclimate. In conclusion, all survey-based data are integrated to proposea physical–environmental design model for courtyards in this region. Proposed model can be generalized to all design cases, where located in BWhs mesoclimate with similar environmental conditions.