Thermal inertia in buildings: A review of impacts across climate and building use

A building with a great amount of thermal mass is able to time-shift and flatten out heat flow fluctuations; this is referred to as the thermal inertia of a building. This paper presents a literature review focussing on the reported impacts of building thermal inertia on thermal comfort and energy use for space heating and cooling. A wide range in research methods, building types and climatic conditions considered by the respective authors, contributes to a large spread in research outcomes. As a general tendency it can be concluded that for most buildings and climates, higher amounts of thermal mass at the inner side of the thermal insulation appear to be beneficial with regard to improving thermal comfort and reducing the energy demand. The impact on energy demand is however relatively small. With an order of magnitude of a few percent for most cases, other design parameters such as thermal insulation of the building envelope and solar heat gains will be more significant. The paper reviews some practical applications exploiting the effect of thermal inertia in design and operation of HVAC systems, and concludes with a discussion on the apparent discrepancy in simulation outcomes and suggestions for further research.