thermal mass

Refers to the thermal storage capacity of a material. Some dense materials have a high capacity to regulate the heating and cooling of adjoining space by absorbing and radiating heat over time. These dense materials can absorb and retain solar energy during the day for gradual release at night or in cool weather; or reduce internal temperatures by drawing coolness from within for release on hot days.

Examples of materials with high thermal mass include masonry, rocks, earth and water.

Thermal mass is generally considered when constructing walls and floors in environmentally friendly buildings. North-facing walls and floors are constructed with high thermal mass materials to increase the passive heating and cooling capacities in those spaces.

Materials with high thermal mass are generally poor insulators – this means that to use thermal mass effectively, external insulation should be considered where relevant.