1 - Heat and mass transport processes in building materials

Abstract

This chapter introduces heat and mass transport in terms of the fundamentals and their application in the field of materials and building physics. It is the scientific topic that underpins all aspects of energy efficiency and thermal comfort in terms of the materials that make up our buildings and occupied spaces. An overview of thermodynamics and the conservation laws are provided to serve as a refresher for some readers and as a basic introduction for others. The chapter then deals with heat transfer by providing explanations of the fundamental science and then applying this to topics that are relevant to material properties and their application in buildings. The introduction of mass to these materials (e.g. water) adjusts the thermal properties, which in turn can alter the driving potentials for mass transport, which affects the thermal properties, etc., hence the true situation in materials is fully transient and highly time dependent. It is essential to consider this for accurate analysis and understanding of fabric behaviour, or of the indoor environment behaviour in response to the fabric it is made of. It is also an essential approach for studying phenomena such as surface and interstitial condensation, mould growth, as well as implications of changes to fabric (e.g. retrofit upgrades) and for thermal comfort. Therefore the next section in the chapter introduces mass transport where the approach is to, again, provide explanations of the fundamental science and then apply this to topics that are relevant to material properties and their application in buildings. Clearly mass transport is a subject in its own right, as is heat transfer. However, the chapter concludes by making the important point that in reality the two occur simultaneously and are inter-dependent, which leads on to the subject of hygrothermal behaviour.