This chapter presents the main physical concepts and basic techniques for natural ventilation and gives orders of magnitude that allow comparing them. Residential and tertiary buildings have been identified as the largest energy end users, mainly for heating, lighting, appliances and equipment. Air-conditioning technology and the availability of cheap energy allowed architects and engineers to keep buildings at a comfortable temperature whatever their orientation, insulation level, shading and thermal mass. Growing evidence shows that individuals are more likely to adapt to seasonal variations when they are given the opportunity to control solar shading and air velocity, thus allowing larger variation range for indoor air temperature when natural ventilation is used. When properly designed, stack ventilation systems use both wind- and buoyancy-driven pressure differences. Double facades can be used for solar-assisted stack ventilation or balanced stack ventilation. The symbiosis of building envelope and building equipment forms the basis for intelligent buildings.
