Passive solar heating has been the subject of many investigations. It is a fact that the largest part of the civilized world lives in places where winter heating is the primary concern of people and the major consumer of energy resources. This chapter describes the large extent methodology of PASCOOL, with complementary material where more novel aspects follow. A major step towards introducing an awareness of passive cooling issues into energy-conscious building design was the European project PASCOOL, which was a continuation of the previous project PASSYS, but focused on passive cooling with emphasis mainly on Southern European countries. The penetration of AC in Southern European and other Mediterranean countries makes it imperative to address passive cooling techniques, be it through heat gain reduction or through the use of natural sinks. Research should be concentrated on the study of the microclimate around buildings, redefining thermal comfort under transient conditions, improving air quality aspects and developing alternative cooling systems.