Case studies provide essential evidence about the performance of buildings. They also illustrate the methods by which a technology can be implemented as well as highlighting problems. Various case study buildings (both new and retrofit) that incorporate mixed mode, natural ventilation and low energy cooling are reviewed in this paper. An outline of the tasks that ventilation is required to perform is also presented. The results show that many buildings perform well and can provide good thermal comfort and air quality for much of the occupied period. Various solutions have been introduced to extend the range and climate in which such buildings can operate. These include pre conditioning the air using underground labyrinths or buried pipes, the inclusion of pre-heating and cooling coils, and the use of thermal mass combined with night cooling. Design and operational faults include incorrect assumptions about heat gains, the failure of components, inaccessible components, structural failures and problems with outdoor air quality. These aspects are described in more detail in the paper.