What should be considered when installing underfloor heating?

Handwerker mit oranger Arbeitsjacke, dunkelgrauer Arbeitshose, gelben Gummistiefeln und einer schwarzen Mütze auf dem Kopf steht in der Mitte eines Raumes, der gerade renoviert wird. Er steht auf den sichtbaren Rohren einer Fußbodenheizung und hat einen Schlauch in der Hand, aus dem Ausgleichsmasse auf die Rohre gepumpt wird.

Underfloor heating is a modern and efficient method to heat the interior rooms. In contrast with conventional heating radiators underfloor heating provides a regular heat distribution in the whole room and is furthermore invisible under the floor covering. A few aspects must be considered when it comes to installation. 

Overview

1. Trend for underfloor heatings

2. What is underfloor heating and how does it work?

3. What should be considered when choosing materials?

4. Which planning and preparation of the floor are necessary when installing underfloor heating?

5. Which consequences has the floor covering on the heat conductivity?

6. Do not forget regular maintenance

7. Conclusion and further information

1. Trend for underfloor heatings

Underfloor heating systems are becoming increasingly popular. No wonder: lower flow temperatures and uniform heat distribution ensure efficient use of heat energy. A well-functioning underfloor heating system therefore contributes significantly to energy efficiency, which in turn saves costs. Underfloor heating is not only, but especially suitable in combination with a heat pump. Heat pumps deliver lower flow temperatures than boilers. Underfloor heating can cope with this aspect better than traditional radiators. Underfloor heating also improves living comfort. It generates more even radiant heat than radiators, which are set significantly warmer. As a result and thanks to a better temperature gradient, residents generally find underfloor heating more pleasant. Cold feet are a matter of the past and comfort in the room is noticeably increased. A high-quality underfloor heating can also increase the value of a property. More and more potential buyers and tenants appreciate the benefits of underfloor heating, which increases the attractiveness of the property.

Good arguments for underfloor heating. Let's first take a look at how underfloor heating works.

2. What is underfloor heating and how does it work?

Underfloor heating is a heating system that is installed under the floor covering to distribute heat evenly throughout the room. There are two main types of underfloor heating systems: water-bearing and electric.

The water-bearing underfloor heating system uses hot water that circulates through pipes in the floor, while the electric underfloor heating conducts electricity through electric heating mats or cables to generate heat. This variant is easier to install and is particularly suitable for smaller rooms or as a supplement to existing heating systems.

With both system types, the heat is then released  upwards and ensures a pleasant room temperature.

3. What should be considered when choosing materials?

The choice of screed is of crucial importance. A heating screed should always be selected, i.e. a screed for which the manufacturer explicitly states that it is suitable for underfloor heating. Care should also be taken to choose screeds with a high thermal conductivity, so that the heat inside the heating pipes is better emitted into the room air instead of creating a heat build-up in the floor. The higher the thermal conductivity, the more efficient the whole underfloor heating construction. In new buildings, screeds with layer thicknesses over the heating pipes of 35 mm according to standards are usually chosen. They serve as a good heat accumulator and release energy into the room for a long time. 

In renovation projects, thin-layer floor constructions with smoothing mortars or levelling compounds are often used for reasons of space and weight. These systems are more expensive and do not store heat for as long, but they are somewhat faster than the more inert new construction systems.

In general, it is advisable to use flow-grade products wherever possible. On one hand, they wrap around the pipes much better and thus ensure additional efficiency of the system. On the other hand, heating screeds should be particularly low-shrinkage and low-tension. Otherwise, there is a risk of crack formation when the screed heats up and cools down. Saint-Gobain Weber offers various high-quality heating screeds, such as weber.floor 4180.

4. Which planning and preparation of the floor are necessary when installing an underfloor heating?

The installation of underfloor heating begins with careful planning and preparation of the floor. Underfloor heating can be installed both in new buildings and retrofits. In new buildings, underfloor heating can be optimally integrated into the building plans, whereas in a retrofit, special attention must be paid to the existing building structure. It is important to ensure that the floor can hold the additional weight of the underfloor heating. In any case, it is advisable to commission a specialized company to carry out the installation. 

Before starting the installation, the floor must be checked and prepared. Old floor coverings must be completely removed, and then the load-bearing capacity of the subfloor must be checked.

Installation depends on the type of underfloor heating. With water-bearing underfloor heating systems, the pipes are embedded into the screed, while electric underfloor heating systems are laid directly under the floor covering or into the tile adhesive. The correct installation technique is crucial for efficient heat distribution. In the case of major unevenness or pipes laid on the bare floor, a level surface should be created using a lightweight levelling compound. Thermal insulation and most often also impact sound insulation are required under every underfloor heating system. The heating energy should be directed upwards into the room and not into the room below. The heating pipes must be checked for leaks and filled with water before the screed or levelling compound is installed. 

The screed or levelling compound is applied in the previously planned layer thickness and is usually pumped to the job site via a hose. The freshly installed surface should be protected from draughts and direct sunlight during the drying time specified by the manufacturer to ensure even drying. The underfloor heating is then heated up and this is documented in a heating log. After this so-called functional heating, the flooring installer measures the residual moisture content of the screed with a carbide hygrometer. If the content is below 2% by weight for cement screeds and below 0.5% for calcium sulphate or anhydrite screeds, the screed is ready for covering and the top layer can be laid. Alternatively, the manufacturer can specify other covering maturities.

5. Which consequences has the floor covering on the heat conductivity?

The chosen floor covering has an impact on the heat distribution of the underfloor heating. While ceramic tiles, for example, enable good heat transmission, thick carpeting can impair efficiency. Suitable floor covering should therefore be chosen according to the heating requirements. Care should be taken to ensure that the floor covering is glued down, so that no entrapped air under the covering could unintendedly reduce the heat even further.

6. Do not forget regular maintenance

Just like for other heating systems, regular maintenance is important to obtain long-lasting efficiency. This includes checking the pipes, venting the system and adjusting the heating curve, if necessary. Long-term efficiency not only contributes to energy savings, but also increases the service life of the system.

7. Conclusion and further information 

In summary, the installation of underfloor heating requires careful planning, high-quality materials and professional execution. The advantages in terms of energy efficiency, room comfort and property value definitely make it an attractive option for modern heating systems. 

You can find more detailed information on the topic of underfloor heatings, such as several recommendations for constructions with underfloor heating or the most important regulations here.