THE SIMPLE CHARACTERISATION OF THERMAL MASS IN BUILDINGS
Authors: Williamson, Terence
Building designers are aware that components of different thermal mass – heavyweight or lightweight – affect the thermal performance of a building. The dynamic thermal behaviour can influence the internal room temperatures, effects of intermittent heating/cooling performance and peak heating/cooling loads. The relative effect of thermal mass in different contexts is however often difficult to assess and the search for a simple metric to describe the effect of thermal mass has been the subject of investigations. This paper gives a brief history of research mainly in Australia aimed at characterising the dynamic thermal performance of opaque building elements. A summary of various mathematical approaches is introduced. Early work at the Commonwealth Experimental Building Station, Sydney (CEBS) and CSIRO, Division of Building Research, Melbourne (DBR) is described and how this work later developed into computer simulation programs. Recent research on the development a mass-Enhanced R-value to characterise the energy performance of concrete sandwich panel walls, and a project that introduces a novel metric (the T-value) to represent the dynamic behaviour of walls is discussed. The paper concludes with speculation on how a simple “thermal mass factor” can be incorporated into the Building Code.