Abu Dhabi, the Capital City of United Arab Emirates, evolved through various stages since its formation. However, unlike other Golf cities, policy makers, planners, and designers sought to guide its growth and development towards a sustainable responsive city. Sustainability has become a central theme of policy and practice, and the design of the built environment is playing a major role towards this. Abu Dhabi developed the World renowned City of Masdar, as a model of sustainable development and design, and established the Estidama Rating System to enforce specific sustainable applications. This aim of this study is to examine the cost-effectiveness of shifting the development of Abu Dhabi from a conventional approach to a sustainable one. In particular, it sought to determine whether vernacular design and architecture could help to address the quest for a sustainable city. The methodology adopted for this research was based on quantitative and qualitative approaches. Three buildings were selected to determine the cost-effectiveness of the proposed sustainable solutions. 1. Masdar building was studied to represent what is classified as a sustainable prototype. 2. Educational Building of Abu Dhabi Police Academy, which has an open courtyard at the centre of the building, represents a vernacular design. 3. Administrative Building of Abu Dhabi Police Academy, which has a closed atrium in the centre without any skylight, represents a conventional building design. The research involved an environmental investigation of power consumption, carbon dioxide emissions, indoor and outdoor temperature, indoor and outdoor relative humidity, and levels of indoor carbon dioxide. Monitors were installed in the three prototype buildings for a period of time, and the results of the readings were compared and analysed. In addition, a questionnaire survey was used to determine the impact of the three buildings on sustainable lifestyles and attitudes. Ninety users of the three buildings responded to the questionnaire. Their responses were also compared and analysed. The results of the monitoring of the thermal performance, power consumption and carbon dioxide levels indoors confirmed that most indoor temperature readings were similar due to the use of air-conditioning in the three buildings. However, cooler temperatures were recorded in similar rates in the alleyways of Masdar and in the courtyard of the Police Academy Educational building. In some cases, courtyard spaces in the Educational Building in the Police Academy recorded even lower temperatures than those of Masdar. These readings were much higher than those of the outdoor exposed temperature, whether in Masdar or in the Police Academy outdoor spaces. Considering that the cost per square meter of the Masdar prototype was almost the double of the other prototypes, these findings challenged the cost-effectiveness of the prevailing Masdar City approach. The results also highlighted the importance of the architectural heritage of Abu Dhabi to address the sustainability agenda, including its implications on planning and building regulations. The findings of the questionnaire survey revealed that there were no significant differences between user responses of Masdar and the Police Academy buildings. These also questioned the cost effectiveness of the Masdar prototype. However, the results also confirmed that the lack of awareness of the sustainability agenda for the users of the three buildings, thus highlighting the wider implications on the sustainability agenda.