Physics - Specific Heat Capacity

In practical terms, it is a useful measure of how much thermal energy can be absorbed by a material. Those with lower specific heat capacities will absorb less and vise versa. This is particularly useful to heating engineers and householders as it enables them to make informed decisions about what materials to use for things like storage heaters and central heating systems.

Central heating systems exist in different forms but the most common ones use water. In such systems, as hot water passes through the system it gradually transfers its stored thermal energy to the surroundings, heating the different rooms in the house. Since water has a high specific heat capacity by the time it reaches the last rooms there will still be enough of the heat it absorbed left to warm them. A substance with a low specific heat capacity would be cold much sooner.

One system that is very popular is underfloor heating. This is not a new idea - the Romans had underfloor heating over 2,000 years ago (look up 'hypocaust' if you want to know more). The most efficient of this type of system, which uses specific heat capacity to the maximum, is to lay a concrete slab as a base. Plastic water pipes are then laid down across the whole surface of the slab and then buried in what is called a 'screed'. The screed is also usually based on concrete. Concrete has a good specific heat capacity - not as good as water but high enough to make it a good heat storage medium. Warm water is then pumped through the pipes and heats up the concrete, which gradually absorbs the heat energy, releasing it slowly into the room. When the water pump and water heater are switched off, the concrete still has a lot of stored heat that it can release into the room. Because the heat is coming from the whole of the floor, it is a very efficient way of heating a building.