The urban heat island (UHI) phenomenon and the dependency of buildings on fossil fuels were the two main issues that formed this dissertation. UHI results in higher air temperatures in dense urban areas compared with their suburbs and rural surroundings. This phenomenon affects human health through thermal discomfort. Furthermore, in the Netherlands, it is estimated that by 2050 the air temperature could be up to 2.3°C warmer as compared to the period of 1981-2010. Besides, the energy consumption of buildings is responsible for 30 to 45% of CO2 emissions. 31% of this consumption belongs to residential buildings. Residential buildings can play a major role in reducing the CO2 emissions caused by fossil fuel consumption. One of the passive architectural design solutions is the courtyard building form. Courtyards have been used for thousands of years in different climates in the world. In hot climates they provide shading, in humid climates they cause a stack effect helping ventilation, in cold climates they break cold winds and protect their microclimate. In temperate climates (such as of the Netherlands), the thermal behaviour of courtyards has been studied less. In this dissertation, low-rise residential courtyard buildings were therefore studied among (and along) different urban block types in the Netherlands. As the first step, computer simulations were done as a parametric study for indoor and outdoor thermal comfort. Field measurements were done in actual urban courtyards and in dwellings alongside urban courtyards in the Netherlands (and in a similar temperate climate in the US). A scale model experiment later followed the simulations. Some of these field measurements were used to validate the simulation models. These efforts answered the two main research questions: 1) To what extent is a dwelling alongside an urban courtyard more efficient and thermally comfortable than other dwellings? 2) To what extent do people have a more comfortable microclimate within an urban courtyard block on a hot summer day ...