Understanding Thermal Mass Design Principles

Thermal mass acts as a "heat bank" during winter and a "cool sink" during summer.  Thermal mass building materials (e.g. mud brick, Timbercrete masonry, kiln fired brick) absorb and release heat energy at the right times to moderate the internal "comfort zone" temperature. The illustrations below explain how thermal mass works.

During a summer day thermal mass materials absorb heat from the hot air inside a home and keep the house cooler.  At night natural ventilation can cool the house by releasing the heat absorbed in the thermal mass materials.

During a winter day thermal mass materials absorb radiant heat from the sun in a well designed and correctly oriented home. At night as the house internal temperature cools down the heat stored is released back into the house to keep it warmer.