Thermal inertia of heating – an advantage or disadvantage?

Thermal inertia of heating – an advantage or disadvantage?

One of the often mentioned features of heating systems is their thermal inertia. Depending on the design and purpose of the building, it can be considered as an advantage or a disadvantage of a particular system. How should this concept be understood?

What is thermal inertia?

Thermal inertia should be understood as the ability of a given body to maintain specific thermal parameters. A heating system with low inertia starts to heat the building in a very short time from starting up the heat source.

 The small heat capacity of individual components makes the system heat up quickly, but also quickly cool down – when the source is turned off, the receivers will almost immediately stop heating. An example of devices characterised by low inertia are water heaters – they have a small water capacity, and the flow rate of the medium is relatively high.

On the other hand, high thermal inertia means a slow heating of the system, but also a long maintenance of heat after the source is shut down. A good example here is underfloor heating.

Disadvantage or advantage?

Low thermal inertia is undoubtedly an advantage when a heating system that quickly responds to a change in settings or ambient conditions is needed in the building. A dynamic rise in temperature is especially desirable in facilities used at certain times of the day. Afer all, a production hall or an office do not need to be heated at full power when no one is working.

Heating with high thermal inertia is more difficult to control. Nevertheless, this feature can be an advantage when the comfort of people who permanently stay in the building matters. Large temperature fluctuations caused by switching the heating system on and off may adversely affect users' well-being. High inertia of the system (e.g. underfloor heating) and the entire building prevent a rapid rise or sudden drop in temperature. Accumulation of heat also positively affects the operation of some heating devices, such as heat pumps, which are sensitive to frequent switching on and off.

Adjust the system to your needs

The general identification of the phenomenon of high or low thermal inertia of the heating system as its disadvantage or advantage is a very big simplification. Much depends on the intended use of the building. In the case of facilities used at a given time during the day (industrial halls, warehouses, office buildings, shops), the dynamics of the heating operation – that is the lowest possible inertia – will probably be more important. In this case, you should choose water air heaters, electrical devices or other systems with forced circulation that accelerates the distribution of heat.

A residential house is a different case – here we usually try to keep the temperature at a more or less fixed level throughout the day. The speed of adjustment will not always be the most important. The slow temperature change in this case gives you more comfort. Its control is more difficult, but not impossible, you should simply plan a specific heating cycle. Radiators or the underfloor heating that slowly reacts to a change in the parameters of supply will be a good choice.