Thermal Mass

The ability of building materials to store heat is referred to as thermal mass. Building materials that have a high thermal mass, such as internal bricks and masonry and a concrete slab with hard floor coverings, can store large amounts of heat without a large temperature change.
In places where the difference between day and night temperatures is eight degrees or more, there are benefits in using high levels of thermal mass inside north-living zones to stabilise internal temperatures in both summer and winter. The correct use of thermal mass inside a house can significantly improve both thermal comfort and energy efficiency.