What is Thermal mass

In simple terms, thermal mass is the ability of a material to absorb, store and release heat.
Materials such as concrete, bricks and tiles absorb and store heat.
- they are therefore said to have high thermal mass.
Materials such as timber and cloth do not absorb and store heat
-  they are said to have low thermal mass.

In considering thermal mass, you will also need to consider thermal lag.
Thermal lag is the rate at which heat is absorbed and released by a material.
- materials with long thermal lag times (for example, brick, thick steel > 6mm and concrete) will absorb and release heat slowly;
- materials with short thermal lag times (for example, thin steel sheeting< 2mm ) will absorb and release heat quickly.