<p>The topic of energy consumption and greenhouse gas emissions in the construction industry has been widely discussed. Passive heating and cooling systems are a viable solution to mitigate these impacts. However, implementing these systems during the building design process faces several obstacles. This research focuses on the barriers to adopting passive systems in residential building design, with a case study of Iran. A mixed-methods approach was adopted to investigate these barriers, which included a literature review, semi-structured interviews, and exploratory and confirmatory factor analyses. The literature review and semi-structured interviews identified different statements that explained the reasons behind the limited adoption of passive systems in residential building design in Iran. Thirty-nine experts in building energy efficiency evaluated 86 statements using a 5-point Likert scale. Through exploratory factor analysis, 17 sub-categories were identified and grouped into financial, social, training, and legal barriers. Confirmatory factor analysis through structural equation models was utilized to examine the interrelationships among the various obstacles to achieve an optimal outcome. To overcome these barriers, modernizing legal policies, emphasizing energy sufficiency and renewable energy sources, in conjunction with energy-efficient systems is recommended. Additionally, architectural education should provide students with the required knowledge and skills for building passive and active system design. Furthermore, energy efficiency systems should be guaranteed by either the government or the private sector, which could enhance aesthetic appeal and symbolic capital.</p>