Thermal Mass Walls

There are two thermal mass walls incorporated into our house, flanking the games room.


The thermal mass walls make a striking, and useful, feature inside the house.

Thermal mass works on the basis that a large amount of energy is needed to heat or cool something that is thick and dense. High amounts of thermal mass in a building stabilise temperatures, as the house is then slow to absorb or release heat and doesn’t respond to the daily fluctuations of temperature. Materials such as concrete and stone provide high levels of thermal mass.


Both mass walls visible from outside the house.

Our two thermal mass walls are made from laterite stone which were sourced from a stockpile at the north end of the farm, cleared out of paddocks in the 1970’s by Davids father and uncles to make way for cropping. There are other types of rock which have higher thermal mass properties, but we chose to make use of what we had available locally.


Construction of the thermal mass walls underway, January 2011

The walls run north-south. They are completely internal walls expect for a 3m length of the eastern wall, which is exposed on one side. It is the intention to provide seasonal cover to this outside section – one day.

In summer, when little to no sunlight falls onto the walls, they remain cool.

In winter, thanks to the full length north facing windows in these rooms, the thermal mass walls receive sunlight – on the eastern side of the walls in the morning and the western sides in the afternoon. The stone traps the warmth from the sun, slowly releasing it back into the house at night, keeping us at a pleasant temperature.


Sunlight falling on the eastern thermal mass wall through the window, late autumn, 2016.