Thermal mass, in the most general sense, describes the ability of any material to store heat.
For material to providea useful level of thermal mass, a combination of three basic properties is required:
- High specific heat capacity-To maximise the heat that can be stored per kg of material.
- High density-To maximise the overall weight of the material used.
- Moderate thermal conductivity-So that heat conduction is roughly in synchronisation with the diurnal heat flow in and out of the building.