How Do I Work?

Evacuating heat by using cooler air outside when available. An open window with a fan will hasten the removal of heat in your home. 

The mass inside the house can be us as thermal storage. By running the fan during a cool evening, your home will start a much lower temperature the next. This can delay the activation of your AC.

Thermal mass is simply any solid or liquid material that can capture, hold, and store heat. Essentially, almost every object inside our homes can be considered to have thermal mass. Everything, from your living room couch, the rug in your dining room, and even the can of soda sitting on your counter, can store heat inside your home.

Thermal mass acts as a thermal battery. During summer it absorbs heat during the day and releases it by night to cooling breezes or clear night skies, keeping the house comfortable. In winter the same thermal mass can store the heat from the sun or heaters to release it at night, helping the home stay warm.

Source: Your Home Australia