A scientific study

Delicate natural stone can be installed on Proline ENERGY without any damage

A scientific study shows that significantly lower deformation behaviour in the Proline ENERGY surface heating and cooling system compared to mineral-based heating screed.



Natural stone flooring is becoming ever more popular. Thanks to the abundance of colours, structures and surfaces, these natural materials are popular particularly among architects. Types of natural stone such as Estremoz, Bianco Perlino and travertine make an impressive display but they are also extremely delicate. This is especially true in regard to their use in conjunction with underfloor heating. In practice, installers who have laid delicate natural stone on common wet systems (heating pipes within the screed) complain about the frequent formation of cracks caused by the low strength of these types of attractive natural stone.

From a physical standpoint, natural stone is the ideal covering for underfloor heating because, compared to ceramic tile, it takes just a fraction of the energy to heat up the material. In addition, the thermal conductivity of natural stone is up to three times better than that of tile. Thus, from a sustainability standpoint, natural stone holds a clear advantage over tile—except for the problem with cracking.  

Proline ENERGY provides a proven solution to the problem. Proline ENERGY supplies underfloor heating in a dry-construction system, offering a very interesting alternative to the classic, very time-consuming process thanks to its lower installation height, shorter installation times and inherently shorter warm-up times.

Manfred Rupprecht, Civil Engineer and Sales Technician at Proline Systems GmbH, reports, "Through our continuous exchange of ideas with natural-stone expert Detlev Hill, it has become clear that our Proline ENERGY surface heating system is the ideal partner for natural stone. A scientific study to demonstrate the decoupling effect of the Proline ENERGY design was conducted under the title 'Deformation of natural stone slabs on underfloor heating systems with low installation height'.

The University of Applied Sciences Augsburg (Faculty of Architecture and Civil Engineering) tackled the problem in the summer of 2016 and worked under the direction of Prof. Dipl.-Ing. (Graduate Engineer) Manfred Schnell to investigate the various deformations of natural stone slabs on heating screeds compared to Proline ENERGY. The student carrying out the experiment, Patrick Allerberger, received scientific support from none other than Mr Detlev Hill, the renowned natural-stone expert in Germany.

Setup and series of tests

The scientific study included six different setups to investigate the various deformation behaviours of the Estremoz, Bianco Perlino and travertine types of natural stone in relation to the heating system in use. The load tests compared the use of a conventional heating system (screed design) to the Proline ENERGY underfloor heating system in two design variants, one in combination with the ENERGY PES decoupling sheet and another with a levelling compound as a load-distributing layer. The natural stone slabs mentioned above were installed on all these design variants. To determine weak points in the slabs and joints, no cross joints were used in these tests; instead, 80 x 20 cm slabs were installed in a running bond pattern and suitable sizes were installed in a modular pattern.

In various heating phases (supply flow temperature of 45/60/65/70 °C) the Augsburg scientists simulated conditions typically found in real-world installations. The measured changes in dimension were evaluated and led to the following result:

Critical deformations and damage when using heating screed
In the test setup with the classic wet system (screed), the natural stone slabs deformed far more than with Proline ENERGY. Furthermore, approximately five days after cooling, cracks became visible on the surface of the Bianco Perlino. Thus it was scientifically determined that the deformation behaviour of a heating screed affected by changes in temperature is significantly greater than with Proline ENERGY BasicLine. The clearly identifiable deformation behaviour of the screed also led to evident damage to the delicate types of natural stone. This damage did not occur in the design using Proline ENERGY BasicLine and ENERGY PES. The maximum expansion values were approximately three times as high for the heating screed as for the dry-construction system. From this, it is evident that the system with Proline ENERGY BasicLine pipe support elements has a much better decoupling ability and protects against deformation damage compared to heating screed.

This made it possible to provide a scientific analysis showing that visually appealing, yet physically delicate types of natural stone, and even types of installations without cross joints, can be used on Proline ENERGY BasicLine with the ENERGY PES decoupling sheet without experiencing damage.

Proline ENERGY – Surface heating and cooling systems in dry construction

ENERGY lets Proline provide two ground-breaking water-based surface heating and cooling systems at once: ENERGY BasicLine (made of expanded polystyrene) and NatureLine (made of soft wood fibres) with laminated aluminium heat-conducting plates. Both systems can be installed as pipe support elements in dry construction without screed. An extremely low installation height (starting at 32 mm) and a low weight per unit area, short response times and low supply flow temperatures of only approx. 30° C put both systems in an optimal position to exceed the German Energy Savings Ordinance (EnEV) 2016 requirements, including for use in renovations.In addition to the technical and economic quality of the systems, the quick and easy installation of ENERGY BasicLine and NatureLine is another feature as well as reasons for the continued success. The heat distribution in the surface is supported by innovative control technologies, which are also offered if necessary.