What Is Thermal Mass?

Basically, thermal mass refers to a material’s ability to absorb and store heat energy. The next question is: what does thermal mass have to do with decorative concrete, and specifically, a polished concrete floor?

Concrete has what is known as high thermal mass. Because it is a dense material, concrete can absorb and store a considerable amount of heat energy. (In comparison, lighter materials like timber can’t absorb and store as much heat. For this reason, timber is known as a material with low thermal mass.) While concrete stores heat energy during the warmer part of the day, it releases this energy when the temperature drops later on. This release can be an efficient way to keep a home warm year round, and polished concrete floors can play a large part in this.

A polished concrete floor, with its high thermal mass, can absorb, store and release heat over a wide area of the home. This should lead to lower heating bills and a more comfortable environment within the home because thermal mass can moderate temperatures, and average out day/night extremes (please ensure you do your research to compare the different products and their performance). But just putting down a polished concrete floor does not guarantee you’ll be able to take maximum advantage of thermal mass. Some key factors should be taken into consideration.

Good planning and design will help to make your polished concrete floor an energy efficient feature, as well as an aesthetically pleasing one. For example, when exploiting thermal mass as a source of passive heating during winter, it should have maximum exposure to sunlight. You’ll need the correct ratio of glazing to concrete to help achieve this. Conversely, minimum exposure to sunlight is required during summer to avoid overheating. With this in mind, shading becomes a very important part of the design process.

The orientation and layout of the floor is something else to keep in mind, as is insulation. Adequate insulation is needed to prevent released heat energy from being lost too quickly. Even floor coverings should be looked at. Polished concrete floors must be exposed to capture heat energy; rugs and carpet act as impediments to thermal mass in this regard.

Thermal mass can also be used to cool a home during summer. It does this by drawing in and storing the heat in the air. As this energy is released later in the day, good ventilation is needed to stop the home from overheating; yet something else to consider. With all these things to think about – and they are worth thinking about for financial and environmental reasons – expert advice should be sought at the planning stages. The Australian government’s Your Home website is a good place to start, and will help to guide you in the right direction should you decide to use the thermal mass of a polished concrete floor as a way to passively heat, and cool, your home.

Images from Australian Government, Your Home