Do Concrete Buildings Disperse Heat Better?

Concrete’s Thermal Properties

• Concrete has excellent thermal mass, or the ability to absorb, store and later release significant amounts of energy, as the Portland Cement Association puts it. Its thermal mass helps homeowners and managers of commercial buildings to save substantially on heating and cooling costs because of concrete’s ability to reduce or at least delay heat transfers. Understanding concrete’s thermal properties and designing buildings to enhance them results in lower energy use, fewer spikes in heating or cooling demand and the ability to shift most energy use to off-peak times when utility rates are lower.

Using Concrete to Cool Buildings

• When the weather is hot, concrete’s thermal mass quickly soaks up that heat gain, helping to keep interior temperatures cool and comfortable. The surface of interior concrete walls and floors stay cool -- below the air temperature -- which creates both radiant and convective cooling. The heat absorbed during the day is lost or dispersed to the cooler night air, especially when windows are opened or the building is otherwise thoroughly vented at night, such as with a whole-house fan. This allows the heat-dispersing cycle to begin again the next day.

Using Concrete to Heat Buildings

• In climates where keeping buildings warm is the main concern, concrete’s thermal mass can help collect and store solar energy -- and heat from other sources used to heat interiors -- and radiate it into building interiors, helping to reduce energy bills. Buildings designed for passive solar energy collection, with south-facing windows, interior concrete floors and other thermal mass collectors, allow low-angle winter sun to shine in. By design, the concrete absorbs that solar heat and later releases it, helping to warm the building at night.

Using Concrete for Radiant Floors

• Embedded tubing or voids in concrete make it possible to heat floors as well as building interiors at very low cost, thanks to concrete’s thermal properties. Radiant floors can also cool floors and buildings. Instead of heating – or cooling – the air, radiant floors spread hot or cold temperatures through the concrete. As the website Green Building Elements explains it, people and pets are more comfortable at lower overall temperatures when floors are warm. The same is true when cooling with radiant floors. Radiant floors thus create comfort with much less energy use.