This thesis presents a new graphic tool to identify and select bioclimatic strategies according to climate conditions and comfort requirements. The Comfort Triangle relates outdoor daily temperature variations with the modification of thermal performance achieved indoors, using two key variables, average daily temperatures and temperature swings. The variation between indoor and outdoor average daily temperature shows the effectiveness of passive heating and cooling strategies, while the relation between indoor and outdoor swings show the capacity of the building to moderate, control or maintain temperature variations in relation to comfort requirements. It is shown that many bioclimatic strategies aim to modify one or both of these variables. Part 1 introduces concepts of bioclimatic design; Part 2 provides a literature review and defines the state of the art in bioclimatic design, while Part 3 describes the development of the comfort triangles for analysis and evaluation of different bioclimatic design strategies. Part 4 tests the tool using case studies at the urban, architectural and building scales, to demonstrate and verify the use of the Comfort triangles in wide range of different climates, situations and building types. Studies using the comfort triangles at the urban scale show how the built environment produces modifications of climatic conditions, modifying the temperature swing and increasing average temperatures. At the architectural scale, studies show the impact of building form, orientation and shading on average temperature and temperature swing. At the construction scale, studies of indoor and outdoor conditions show the results of different materials used in different climates. The Comfort Triangles clearly identify the impact of the built environment, permitting a visualization of the change in two key vectors, average temperature and temperature swing. The final part of the thesis analyses the results of the case studies to show the value of this new graphic tool that offers a valuable complement to existing bioclimatic design tools, emphasizing the dynamic nature of thermal performance in natural conditioning. It is shown that the comfort triangles provide a new way to analyse projects in different climates and promote the selection of appropriate bioclimatic design strategies.