Formal sustainability in Iran’s arid regions: optimizing thermal performance through vernacular bioclimatic strategies

Vernacular architecture in Iran’s arid regions reflects climatic adaptation, socio-cultural identity, and spatial logic, yet its translation into formal sustainability frameworks remains limited. This study examined formal sustainability in 20 historical structures across Isfahan, Kerman, Shiraz, and Yazd using spatial documentation, semi-structured expert interviews (<i>n</i> = 12), and literature-derived data. Results show courtyard-centered layouts, adobe walls, and passive systems – particularly windcatchers (badgirs) and double-layer domes – reduced cooling loads by up to 70%.  Socio-spatial features such as andaruni/biruni zoning create thermal gradients that enhanced microclimate control while reinforcing cultural resilience. Material intelligence, including high thermal mass and albedo optimization, further supported energy efficiency and replicable design. Although direct measurements were unfeasible, triangulated evidence enabled a contextualized framework for passive integration.  Addressing regulatory and material constraints, policy incentives are proposed to scale vernacular techniques in urban housing. Ultimately, a thermally grounded model links vernacular architecture to energy efficiency and formal sustainability in arid regions.