Heating costs in operation
Reduce heating costs by approx. 5-20% with Retanol® screed! Click here for the video:
THERMAL CONDUCTIVITY RETANOL® SCREED
Due to its higher bulk density, a Retanol® screed has a better thermal conductivity of up to 2.4 lambda (V). Compared to a calcium sulphate screed with poor thermal conductivity, the energy-efficient Retanol® screed transports more energy to the screed surface in the same amount of time. The result: the higher the thermal conductivity, the more efficient the underfloor heating.
More energy at the same flow temperature with Retanol® screed
The theory is logical. What does it look like in practice? The results of the test are shown in the thermal images. The fields with 65, 45, 35 and 30 mm pipe overlap are arranged from left to right. The cross-sections are also visualised in the diagram below the thermal images. The screed thus becomes thinner from left to right and more stable in its properties with Retanol® F5 and F6 (flexural tensile strength). The pipe cover can therefore be reduced compared to a zero screed. The results are clear: the thinner the screed and the higher the strength and thermal conductivity, the more heat/energy reaches the surface. Compared to the calcium sulphate screed with 65 mm pipe cover (top left), the Retanol® F6 screed (right) is 3.3 °C warmer on the surface.
The heating curves as a solution for lower energy costs
The recording of the heating curves of the individual fields illustrates what is possible with a Retanol® screed compared to a zero screed. It is clear that the aim is not to quickly heat up the screed and thus the room, but to lower the flow temperature with a Retanol® screed compared to a zero screed. If we take the CT-F4-H45 curve (zero screed with 45 mm heating pipe overlap) as the optimum heating curve and therefore heating speed, then the flow temperature would have to be increased for the heating curves/screeds below in order to supply the room with the same amount of energy as our initial curve/zero screed. The situation is similar with the curves above, i.e. Retanol® F5-H35 and Retanol® F6-H30, but here the flow temperature does not have to be increased, but can be lower than the flow temperature for our initial curve/zero screed as F4 with 45 mm pipe overlap.
HEATING CURVE SHIFT WITH RETANOL® SCREED
This derivation can now be transferred to the heating curve. A heating curve is generally set by the heating engineer. The heating curve defines the flow temperature with which the underfloor heating is controlled depending on the outside temperature. The colder it is outside, the higher the flow temperature must be in order to achieve the desired temperature in the house/flat. Flattening the heating curve thus reduces the energy required to bring the water to the desired flow temperature at any given time. This is exactly what is possible with a Retanol® screed and is shown in two steps in the diagram. Step 1: flattening the heating curve by reducing the nominal thickness so that the heat has a shorter path to the surface. 2nd step: the further flattening of the heating curve due to the higher thermal conductivity, as a Retanol® screed has a lower thermal resistance and therefore the heat reaches the screed surface more effectively.
COP value as a function of the flow temperature for heat pumps
For heat pumps in particular, the low flow temperature plays a decisive role in increasing efficiency. The COP value (coefficient of performance) describes the ratio of the heat output of the heat source and the required drive energy (electricity). With a COP value of 4, 1/4 of the energy provided is the amount of electricity, e.g. from the power grid. This means that the higher the COP value, the more efficient the heat pump. Two things can be seen in the graph. Firstly, the COP value increases as the outside temperature rises (air source heat pump). This is due to the fact that the delta between the heat source (air) and the flow temperature becomes smaller and therefore less electricity is required. The second effect is that the curve describing the COP value increases disproportionately with a lower flow temperature. This means that the percentage energy saving also increases as the flow temperature falls. In figures, this means that a reduction from 65 to 60 °C only results in a COP value increase of 0.2. Lowering the flow temperature from 40 to 35 °C increases the COP value by approx. 0.7, making a Retanol® screed the second component for more sustainable heating alongside the heat pump.
Energy efficiency classes with RETANOL® screed
The bulk density of a Retanol® screed and the thermal conductivity increase with the screed quality. At the same time, the nominal thickness can be reduced depending on the surface load.
The zero screed has the energy efficiency class EK 0. The table shows the nominal thicknesses that can be achieved with EK 1 to EK 3 with Retanol® screed.
| Energy efficiency class | 2 kN/m² | 3 kN/m² | 4 kN/m² | 5 kN/m² | 7,5 kN/m² | 10 kN/m² |
| EC 0 C25-F4* | H45 | H55 | H65 | H75 | n.a. | n.a. |
| EC 1 C35-F4 | H40 | H50 | H55 | H60 | n.a. | n.a. |
| EC 2 C40-F5 | H35 | H45 | H50 | H55 | H75 | H90 |
| EC 3 C40-F6 | H30 | H30 | H40 | H45 | H70 | H85 |
*Cement screed/Untreated screed
- The energy efficiency class is determined by the screed quality and the minimum or maximum nominal thickness (minimum nominal thickness + 5 mm)
- For thicknesses of more than 10 mm including the tolerance, the energy efficiency class is reduced by one class.
The reduction is repeated every 10 mm. - The higher strengths are accompanied by the following advantages in terms of the energy efficiency of a Retanol® screed:
× Higher bulk density and lower air void content
× Higher thermal conductivity
× Nominal thickness reduction - EK 1/2 = e.g. Retanol® EKA, Retanol® Reducer 48, Cored® Reducer 48
- EK 3 = e.g. Retanol® Xtreme
Heating cost savings with Retanol® screed
The reduction in flow temperature can be determined from the excess energy/surface temperature depending on the energy efficiency class. This means that the flow temperature in residential buildings can be reduced by between approx. 3 and 4 degrees compared to a zero screed. This results in energy savings of 7.5 to 10 %.
HEATING COST SAVINGS OVER 50 YEARS WITH RETANOL® EK 2 FOR DISTRICT HEATING
Expressed in figures, a Retanol® screed and a district heating connection will save you €50/m² over 50 years, based on approx. 10 % energy savings with EK 2.
| Screed | Costs/m² | Savings/m² |
| Untreated screed | 500 € | |
| Retanol® screed | 450 € | 50 € |
HEATING COST SAVINGS OVER 50 YEARS WITH RETANOL® EK 2 FOR HEAT PUMPS
Expressed in figures, a Retanol® screed and a heat pump will save you €66/m² over 50 years,
assuming approx. 10 % energy savings with EK 2.
| Screed | Costs/m² | Savings/m² |
| Untreated Screed | 660 € | |
| Retanol® screed | 594 € | 66 € |
WE WILL FIND THE PERFECT SOLUTION FOR YOU!
PCT Performance Chemicals GmbH Ltd.
Tel.: +44 (0) 1925 500845
E-mail: enquiries[at]pct-chemie.com
WE WILL FIND THE PERFECT SOLUTION FOR YOU!
PCT PERFORMANCE CHEMICALS GMBH
Tel.: +49 7159 4062-0
E-mail: info[at]pct-chemie.de