What’s thermal mass?
When you leave a brick in the sun for an hour and then take it inside into a cool room, the brick stays warm, retaining the heat from the sun. Likewise, taking a cool brick out into the sunshine, the brick will take longer to heat up than for example a thin sheet of metal. This illustrates the principle of using heavy, dense materials such as concrete in a building, increasing its thermal mass. It means that less energy is used to heat the building up or cool it down, (technically, regulating internal ambient temperature) as and when the outside temperature fluctuates: night and day, or in winter and summer. The soil on the roof adds thermal mass and helps to reduce energy use making the Lowhouse a more sustainable home.
