• Renovation
  • Radiators
  • Underfloor heating

Reduced energy cost with low temperature solution 

A successful case study from Germany shows how households can dramatically reduce their energy costs in one fell swoop with the help of the expertise of Purmo.
Ulow E2 hallway

Clearly defined targets for temperature reduction

In this case, the owner and developer of the house, which dates back to 1990 and has a total of three storeys, decided to replace his old oil heating system (70/55) with a modern heat pump system (40/35) and to convert to a surface heating system used in combination with state-of-the-art low-temperature radiators. This would allow the temperatures within the heating system to be drastically reduced, which would result in lower energy consumption and low distribution losses.

Special solutions required due to restrictions

A number of limiting factors had to be taken into account here during the practical planning phase. For example, the low ceiling height in the basement ruled out the installation of conventional underfloor heating and the use of wet screed was not possible. The installation of radiators was not an option either and also not desired due to the limited amount of space.

Special solution with milling system for the basement

This meant that a special solution had to be found for the basement: a milling system developed especially for this purpose. This system, which involves milling channels in the existing screed and setting the pipes into them, offers obvious advantages: no increase in the height of the floor structure, no introduction of moisture, no drying time, full compatibility with all standard floor coverings, and an ideal installation spacing of just 12.5 cm. Other features, such as the very high heating capacity, the excellent controllability thanks to the low construction height, and the practically 100 % dust-free installation were also decisive factors (also ideal for clinical areas). Furthermore, the floor layer can start laying the floor covering without delay.

Flexible milling system

The milling system requirements are very flexible, however: the existing screed only needs to be about 40 mm thick to allow milling of the channels. Of course, the screed has to be dry, load-bearing, smooth, levelled and free of any pipes, cables or conduits. A short site visit was agreed to check the feasibility.

Rapid construction progress with milling system

The channels were quickly milled in the existing screed, after which the underfloor heating pipes, 14x2 mm, were laid with a pipe spacing of 12.5 cm. Then the stainless-steel heating circuit manifold with adjustable flow meter was installed. The underfloor heating system was then filled and vented and a leak test was carried out. The client was given a briefing and again made aware of the 10-year warranty that Purmo gives on all surface heating systems as part of the FLOORTEC Complete System Warranty.

Flexible solution for the ground floor with the FLOORTEC Dry System

On the ground floor, it was not possible to use conventional wet screed because the static load would have been too great for the wooden beam ceiling to support. Due to space limitations, the client was unhappy with the alternative of using radiators. The heating contractor therefore decided to use Purmo’s FLOORTEC Dry System, whose product properties satisfied the existing conditions: the low weight of approximately 14 kg/m² (including dry screed panels) and the very high load-bearing capacity of up to 5 kN/m² were the decisive factors, in addition to the fact that no moisture was introduced, no drying times were necessary and compatibility with all common floor coverings was ensured. Here too, the floor layer was able start work immediately.

Low installation height with dry system

Particular emphasis was placed on ensuring very good controllability by keeping the construction height to a minimum: a total thickness of just 35 mm was achieved by using 30-mm-thick EPS elements, which accommodate the 16x2 mm composite pipes, and a 5-mm-thick load distribution layer (strongboard) on which tiles, laminate and parquet thicker than 15 mm can be laid directly. The excellent heat distribution and the resulting uniform heat in the room were also important to the client. These requirements were met mainly thanks to the FLOORTEC Dry System, which has full-area aluminium lamination laid directly on the system element where the pipes are curved.

Low-temperature radiators on the upper floor ensure excellent controllability 

At the request of the client, ULOW-E2 low-temperature radiators from Purmo were installed in the bedrooms and workrooms on the upper floor. These offer up to 80% more output than conventional radiators and allow quick adjustments to thermal comfort, even with compact radiator dimensions and low temperatures of less than 40° C. This means that the ULOW-E2 runs at the same temperature level as the underfloor heating system – in other words: no second mixed circuit (no mixer, pump, control unit etc.) is required.

ULOW-E2: dynamic increase in output on demand

The rapid response heating function (boost mode) of the ULOW-E2 increases the radiator output even further – in our example, from 1027 W to 1247 W.
The ULOW-E2 radiator system used here also offers further advantages: the option of switching from heating to cooling or “ventilation”, a central connection system for flexible installation, temperature difference control by means of room and flow sensors (fans only run if delta T > 3K), and very quiet operation (only approximately 25-28 dB in comfort mode). The operating voltage is between 5 and 12 V and the power requirement of the fans is about 0.7 W. The client also had strict requirements regarding room aesthetics. These were easily satisfied by the elegant design of the ULOW-E2, which has been awarded the RedDot design award.

Summary: Heating costs effectively reduced

The building was refurbished without any problems and in accordance with the specifications, using different heating surfaces in each case. The specifications regarding temperature, output and weight were met and it was even possible to lower the temperature further, by as much as 2 to 3 K, resulting in an additional reduction in operating costs. Reducing the flow temperature by just 5 K cuts the operating costs by 10 to 15%. Also, the heating surfaces are now equipped to efficiently transfer low temperatures to the rooms in the future. This would be useful, for example, if a solar system is fitted at a later date. The refurbishment will not only continue to be kind to the customer’s pocket in the future but also to the environment, thus improving the quality of life for future generations.