Over the past century, the urban population in the urban centres in Malaysia had significantly increased in size through extensive migration. Terrace houses have become the most common urban habitats in the densely populated urban centres throughout Peninsular of Malaysia in recent decades. / There is an on-going concern on identifying efficient ventilation and lighting solution for local housing. This research thesis focuses on ventilation components, specifically the air-well, which is a traditional mechanism to provide natural air-flow and natural day-lighting. It will explain the morphological transformation of the air-well in the design of terrace houses in the city of Johor Bahru in the past three and a half decades. First of all, this thesis introduces the role of the air-well in the design for local urban habitats of terrace houses with air-well. In addition, it explores the impact of the use of the air-well on the design trends of terrace houses. / As Tetsu Kubota and Supian Ahmad have identified in their recent research that with the global energy crisis and population growth, a few of issues concerning the design of terrace houses have emerged: (a) How have the local architects adapt the design of air-well in terrace houses to achieve a passive design in achieving good natural ventilation and natural lighting in a high density urban habitats? (b) How has the design of the air-well evolved with the changing needs of local inhabitants of terrace houses from the 1970s to the year 2005? / This thesis focuses on the provision for natural ventilation and natural lighting under Malaysian Uniform Building By-laws in terrace houses design from the 1970s to the year 2005 in Johor Bahru. In order to evaluate the design development trends for terrace houses in Johor Bahru in the past three and a half decades, six houses have been identified as specimen based on a list of formulated criteria. These six selected houses have been used as case studies in the core research work for this thesis. The examination started by studying the design for each house by means of gathering three main types of drawings for each house: plans, elevations and sections. From these six cases, a historical trajectory of design trends as evolved over these decades in Johor Bahru is identified. Then from the drawings gathered, the design performance in the provision for natural ventilation and natural lighting for each house by utilising the Y-architects’ natural ventilation and natural lighting calculation table has been carried out. / The evolution of the air-well in terrace houses have been discussed in the final chapter and it can be divided into three main phases over the identified historical time line: introduction of the air-well from 1884 to the 1970s; the elimination of the air-well from 1980s to the year 2000; and a re-conciliation of the air-well from around 2005 onwards. / Finally, this thesis concludes with observations on the design idea of the air-well, as a fundamental intelligence. The air-well not only provides a good relation with nature, but also a passage to an essential amenity.