The fact that people spend a major part of their lifetime indoors, together with the lethal COVID-19 pandemic which caused people to spend even more time inside buildings, has drawn attention to the significance of achieving Agenda 2030 SD goal number three: good health and well-being, in reference to the indoor environment. The research subject is the health and well-being of building users explored through the sustainable (passive) design principles having an impact on the comfort and quality of the indoor environment. It is set within a regenerative sustainability framework encompassing the physiological, biophilic, psychological and social aspects of comfort. The Comfort Assessment Model’s categories, to some extent, rely on the first author’s doctoral thesis, with further modifications regarding the passive design criteria and indicators. A comparative analysis of the model with international sustainability certification (rating) systems has been performed, proving the significance of introducing more passive design comfort (health) related criteria into sustainability assessment models. In addition, a focus group of expert architects contributed to the research conclusions by responding to a questionnaire addressing the issues of sustainability, comfort and passive design, in terms of the health and well-being of building users, which confirmed the relevance of applied passive design measures for providing comfort indoors and fulfilling sustainable development goals.