Based on Parts I and II, the need for a different view on IEQ is emphasized, including ‘new’ assessment procedures and models as well as the need to consider the built indoor environment as a system with sub-systems. A view in which IEQ is approached in an integrative multi-disciplinary way, taking account of possible problems, interactions, people and effects, focusing on situations rather than single components. While currently available performance indicators for healthy and comfortable indoor environments are presented and discussed in Chapter 8, Chapter 9 presents available information for defining a conceptual framework of cause-effect relations (patterns) for different scenarios (homes, schools and office buildings) and for major end-points (e.g. asthma, learning ability, productivity, and dry eyes and skin).