Concrete Slab - Thermal Performance

Thermal Performance

There are two main thermal considerations. The first is the question of insulating a floor slab. In older buildings, concrete slabs cast directly on the ground can drain heat from a room. In modern construction, concrete slabs are usually cast above a layer of insulation such as expanded polystyrene, and the slab may contain underfloor heating pipes. However, there are still uses for an uninsulated slab, typically in outbuildings which are not heated or cooled to room temperature. In those cases, casting the slab directly onto a rocky substrate will maintain the slab at or near the temperature of the substrate throughout the year, and can prevent both freezing and overheating.

The second consideration is the high thermal mass, which applies to walls and floors, or wherever the concrete is used within the thermal envelope. It is a disadvantage where the rooms are heated intermittently and require a quick response, as the concrete takes time to warm up, causing a delay in warming the building. But it is an advantage in climates with large daily temperature swings, where the slab acts as a regulator, keeping the building cool by day and warm by night.