Bad experiences with construction quality, the energy crises of 1973 and 1979, complaints about "sick buildings", thermal, acoustical, visual and olfactory discomfort, the need for good air quality, the move towards energy efficiency, decarbonization and sustainability ? all these have accelerated the development of a discipline that, for a long time, was hardly more than an academic exercise: building physics. The discipline embraces domains such as heat and mass transfer, building acoustics, lighting, indoor environmental quality, energy efficiency, and, in some countries, fire safety. Through the application of physical knowledge and its combination with information coming from other disciplines, building physics helps to under-stand the physical phenomena governing building parts, building envelope, whole building and built environment performance ? called urban physics. Today, building physics has be-come a key player on the road to highly performing new buildings and renovations.
This book deals with heat, air and moisture transport in building parts or assemblies and whole buildings with emphasis on the building engineering applications.
Compared to the third edition, this fourth edition has been expanded in chapter 1 to include the physical determination of the thermal conductivity of materials, together with an in-depth discussion of all the effects of thicker insulation layers. In chapter 2, additional information has been added on wind pressure and the evaluation of condensation inside the building com-ponents, while a new chapter 4 on material properties has been included. The whole book, including the figures, has been revised and restructured where necessary.

Dr. Ir. Hugo S.L.C. Hens is an emeritus professor of the University of Leuven (KULeuven), Belgium. Till 1972, he worked as a structural engineer and site supervisor at a mid-sized architectural office. In 1975, after his predecessor and promotor professor A. de Grave suddenly passed away and after defending his PhD-thesis, he stepwise developed the unit Building Physics at the Civil Engineering Department. He taught Building Physics from 1975 till 2003, Performance Based Building Design from 1975 till 2005 and Building Services from 1975 till 1977 and from 1990 till 2008. Hugo Hens authored and co-authored 68 peer reviewed journal and 174 conference papers about the research done, helped curing hundreds of building damage cases and acted as coordinator of the CIB W40 working group on Heat and Mass Transfer in Buildings from 1983 till 1993. Between 1986 and 2008, he was operating agent of the Annexes 14, 24, 32 and 41 of the IEA EXCO on Energy in Buildings and Communities. He is a fellow of the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE).

Introduction
1. Heat Transfer
1.1 Generalities
1.2 Conduction
1.3 Heat Exchange at Surfaces by Convection and Radiation
1.4 Building Related Applications
1.5 Problems
2. Mass Transfer
2.1 Generalities
2.2 Air
2.3 Water Vapour
2.4 Moisture
2.5 Problems
3 Heat, Air, and Moisture Combined
3.1 Why?
3.2 Material and Assembly Level
3.3 Whole Building Level
3.4 Problems
4. Heat, Air, Moisture Material Properties
4.1 In general
4.2 Dry Air and Water
4.3 Thermal Properties
4.4 Air Properties
4.5 Moisture Properties
5. Postscript
6. Problems and Solutions