How the thermoacoustic cooling works in the control

Cooling underfloor heating: perfect against heat

Our summers are now tough: every year, waves of heat reach us. But only a few can afford an air conditioning system or have the conditions for installation. However, modern underfloor heating can also work in the other direction and cool the room.

Underfloor heating can be adjusted to heat in winter and cool in summer.


A heater should warm rooms and also cool them? What may sound strange at first, has long since ceased to be contradictory in practice. The laws of physics allow a temperature control system that works in both directions. With the noticeably warmer periods in summer, consumers are increasingly interested in alternative cooling methods, as air conditioning systems are often associated with high acquisition and operating costs. Existing underfloor heating is suitable as a cooling element: What works with hot water can be reversed with cool water.

A reversible heat pump is required for this. This uses the ground to transport the warmth of the earth's interior into the house in winter or to release the warm room air to the environment in summer. Because the earth has an ideal property for this: it only warms up superficially in summer and freezes only a few centimeters deep in winter. In the layers below (up to 50 meters), however, the temperature remains relatively constant at around 10 degrees Celsius.

How does cooling heating work?

The prerequisite for the reversible function is a surface heating system: The most popular system is underfloor heating. Whether heating or cooling is required - the same distribution network can be used. However, it must be ensured that the cooling water flow temperature is at least 18 degrees (two-pipe system) so that no condensation can form. Otherwise the floor covering can be damaged or mold can form. With an increased building cooling load, two-line systems are no longer sufficient. Larger buildings or rooms with large glass surfaces in particular require more cooling and are therefore dependent on four-wire systems. In such systems, separate distribution systems are used for heating and cooling.

Whichever distribution system is chosen: a modern heat pump is a must to effectively cool rooms. The principle of a heat pump is similar to that of a refrigerator. The heat pump also has an evaporator, compressor, condenser and expansion valve. If you want to use the heat pump for cooling, it can be enough to reverse the direction of flow of the compressor and the expansion valve. In addition, depending on the required cooling capacity, the user can choose between two different variants, passive or active heat pump cooling.

Passive cooling by means of a heat exchanger

In principle, this is "natural" cooling with the help of a heat pump. As long as the room temperature in summer is above that of the ground, the heat can easily be transported down into the geothermal probes via a heat exchanger. This cooling principle is based on the temperature difference between the earth and the house.

Only a few elements such as heat exchangers, valves and a circulation pump are required for this cooling process. The disadvantage is the low performance that cannot compete with air conditioning systems. One advantage is the particularly energy-saving factor, since there is only a low power consumption for the circulation pump. A cost-efficient variant, which, however, could be too weak in midsummer, depending on the space and size.

Actively lower the room temperature

With active cooling, the entire heat pump cycle is reversed. If an air source heat pump can extract heat from the outside air, it is also possible to extract heat from the inside air. Active cooling is suitable for both geothermal heat pumps and air-water heat pumps. The extracted heat is transferred to the actual (e.g. earth) with the help of the compressor, which in this reverse scenario serves as a heat receiver / heat sink. This actively reduces the room temperature.

To do this, a 4-way valve and a second expansion valve must be installed in the cooling circuit. Even if the active cooling has a higher power consumption than the passive method, the energy balance is in the green area compared to cooling systems such as air conditioning. The great advantage of active cooling is also the cooling capacity, which can easily reach a room temperature of 20 ° Celsius in summer and, unlike air conditioning, does not dry out the air.

Smart control of the cooling and heating system via WLAN

Thanks to new technological achievements, the control of such cooling and heating systems is also becoming more and more intelligent. There are already providers of smart home solutions that work via the WLAN network. It doesn't matter whether there is an internet connection - the house's internal WiFi network alone is sufficient for mobile control. For example, a house can have different heating zones that are individually regulated.

It can be controlled using mobile devices such as smartphones, making it a solution that can be conveniently carried out from the couch. The smart control can take place in real time or plan which temperature should prevail and when. If you are currently on vacation and would like to arrive at a cool home afterwards, you can set it up on your smartphone beforehand.

Can I retrofit underfloor heating?

In principle, this is possible with certain renovation solutions. There are several underfloor heating systems that are suitable for retrofitting. Interested parties should try to compare the various manufacturers. Simple assembly should be guaranteed even in difficult circumstances. It is important, for example, that the system is installed directly on the existing substrate such as screed, tiles or wooden floorboards. Elaborate demolition work is not necessary.

What are the advantages and disadvantages of cooling underfloor heating?

On the one hand, there is a high level of living comfort: because those who use underfloor heating for heating and cooling ensure pleasant temperatures all year round. If geothermal or water heat pumps are used that are equipped with a passive cooling function, the operating costs are low. On the other hand, however, there is the limited output of the heating. The surface heating can only dissipate part of the excess room heat with high heat loads. In order to compensate for this disadvantage as much as possible, ideal planning is necessary.

A contribution by:

  • Nick Gretzinger

  • Sarah Janczura

    Sarah Janczura is content manager and responsible editor for After an internship with a focus on social media, she worked as an online editor in a digital agency. She writes about technology, research and career topics.