REFURBISHMENT WITH RETANOL® SCREED
The two main reasons for renovating a screed are:
1. the increase in living comfort through underfloor heating and
2. the change from radiators to underfloor heating.
This enables a lower flow temperature. This in turn is absolutely essential for heat pumps and is the key to lower heating costs.
In most cases, the biggest challenge in an energy-efficient renovation with underfloor heating is the lack of installation height.
This is due to the fact that the floor structure was previously designed and constructed without underfloor heating. A heated screed is generally thicker than an unheated screed, as the heating pipe must be added to the minimum nominal thickness of 45 mm (pipe cover). This results in a layer thickness of approx. 65 mm for a zero screed. This rule does not apply to a Retanol® screed. In plain language, this means that you can realise a screed thickness including heating pipe of 35 mm in residential construction with Retanol® Xthinn NeaTherm. Compared to a screed without Retanol®, you save 30 mm construction height and can install a screed with underfloor heating despite the low construction.
RETANOL® SCREEDS OFFER MAXIMUM IMPACT SOUND INSULATION
A thin-layer screed makes it possible to increase the nominal thickness of the substructure (impact sound insulation, thermal insulation or levelling) depending on the available construction height. This is an important feature, especially for impact sound insulation, in order to guarantee living comfort. As a rule, the thinner the impact sound insulation, the lower the impact sound improvement factor. There are solutions in the 5-10 mm range made from PUR-bonded rubber fibres, for example, which have a good impact sound improvement factor, but are generally quite cost-intensive. These solutions make sense if Retanol® Xthinn NeaTherm (35 mm with heating pipe) does not provide more than 5-10 mm of impact sound insulation. This structure is shown in the diagram on the left.
EPS impact sound insulation is generally cheaper than bonded rubber fibres and starts at a nominal thickness of 15 mm (as a tacker board to support the underfloor heating). Here too, the thicker the material, the higher the impact sound improvement factor. The specifications for impact sound improvement and the nominal thickness depend on the manufacturer. The solution with Retanol® Xthinn NeaTherm and 15 mm EPS impact sound insulation is shown in the centre of the diagram.
The more structure available, the thicker the impact sound insulation and screed can be. If, for example, the maximum impact sound insulation has been achieved with 25 or 30 mm and there is still enough construction height available, a screed with Retanol® Xtreme NeaTherm and a pipe cover of 30 mm can be installed. The higher mass of the screed in turn increases the impact sound insulation. The diagram on the right shows the structure. Mineral wool can also be used as an alternative to EPS impact sound insulation.
It is important to note here that increasing the impact sound insulation in relation to the screed mass has a much greater effect on impact sound insulation. It is therefore advisable to maximise the impact sound insulation and cover the rest of the structure with a Retanol® Xthinn NeaTherm or Retanol® Xtreme NeaTherm screed. This allows you to achieve the best possible living comfort.
Features Retanol® Xthinn NeaTherm IN COMPARISON WITH Retanol® Xtreme NeaTherm
| RETANOL® XTHINN NEATHRM | RETANOL® XTREME NEATHERM | |
| Minimum pipe cover | 20 mm (35 mm with pipe) | 30 mm |
| Drying times | After the 6th day | After the 5th day |
| Heating phase | 5 days | 4 days |
| Screed quality | F6 | F6-F8 |
Thin layer with the ideal bulk density and therefore mass
The bulk density of a Retanol® screed is approx. 2,200 kg/m³, which equates to 22 kg/m² per 10 mm screed thickness. A Retanol® Xthinn NeaTherm screed with a total thickness of 35 mm therefore weighs more than 77 kg/m². This corresponds to approx. 60 % of the weight of a conventional cement screed (1,800 - 2,000 kg/m³) with a nominal thickness of 65 mm and is therefore ideal for structures with a low construction weight. At the same time, a Retanol® screed has enough mass to ensure impact sound insulation. We can check which solution makes the most sense for your project in a personal discussion with one of our consultants.
Basis weight Retanol® Xthinn NeaTherm
| Screed type | Nominal thickness | Weight kg/m² per mm | Basis weight/m² |
| Untreated screed | 65 mm | 2,0 kg/m² | 130 kg/m² |
| Retanol® Xthinn NeaTherm | 35 mm | 2,2 kg/m² | 77 kg/m² |
Our Agent products
Jointless with shrinkage class SW 1 acc. to DIN 18560-1/BS 8204* with Agent X®
*UK only
Energy-efficient refurbishment with Retanol® screed
A thin-layer Retanol® screed has another very important advantage, especially when carrying out an energy-efficient refurbishment with a heat pump. As a radiator, the thermal conductivity and nominal thickness of the screed is the decisive factor for efficient heating. High thermal conductivity and a thin-layer screed can significantly improve the efficiency of underfloor heating. The flow temperature can be reduced with a Retanol® screed compared to a conventional screed. This correlation is the key to greater efficiency, especially for heat pumps. Lowering the flow temperature by 1 °C reduces energy costs by approx. 2.5 %. Depending on the initial situation, the flow temperature can be reduced by approx. 2-8 °C. As a result, a Retanol® screed reduces heating costs by approx. 5-20 %. This advantage is included in a renovation screed with Retanol®.
Find out more about lowering the flow temperature and adjusting the heating curve here:
Results of the thermal images
Die ThThe theory is logical. What does it look like in practice? From left to right, the fields are arranged with 45, 30 and 20 mm pipe overlap. The cross-sections are also visualised in the graphic 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 an untreated 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 untreated screed with 45 pipe overlap (top left), the Retanol® Xhtinn NeaTherm screed (right) is 4 °C warmer than the zero screed at the same flow temperature.
TEMPERATURE CURVE
As can be seen in the graph, 20 minutes after the start of the heating phase, the measured temperatures in the measuring field are at a constant distance. This temperature difference remains approximately the same over the entire heating process. Above all, the curves do not equalise.
This in turn means that a Retanol® screed can be heated with a lower flow temperature compared to a conventional screed in order to achieve the same heating behaviour and thus the desired room temperature compared to a untreated screed.
Reducing heating costs with Retanol® Xthinn NeaTherm
Before starting the floor covering work, functional heating in accordance with DIN EN 1264-4/BS EN 1264* is carried out from the 21st day after screed installation to confirm the function of the underfloor heating. The screed is then heated to support the drying process. The screed is heated until it is ready for covering. This heating process takes at least 26 days and is absolutely essential for the progress of the construction process in preparation for the floor covering work. The costs incurred by district heating, heat pumps or external heating sources are hidden costs that are not usually calculated. With an external electricity-powered heating source, costs of up to 40 euros per m² can be incurred for the heating phase of 26 days. This means a doubling of the calculated screed costs. The solution to reduce these costs is the shortened heating phase of Retanol® Xthinn NeaTherm, whereby the heating phase can be reduced to five days. This saves you more than 5 euros/m² with district heating and up to 33 euros with an electricity-powered external heating source. In most cases, the reduction in heating costs is greater than the investment in Retanol®. This means that Retanol® reduces your construction costs compared to a zero screed.
*UK only
You can find detailed information about the heat sources and their consumption here:
| RETANOL® | Untreated screed | |||||
| Heat source | Costs* | Heating days | Expense** | Heating days | Expense** | Savings** |
| Extern Öl | 0,78 € | 5 | 3,50 € | 26 | 20,28 € | 16,78 € |
| External power | 1,54 € | 5 | 7,70 € | 26 | 40,04 € | 32,34 € |
| Heat pump | 0,47 € | 5 | 2,35 € | 26 | 12,22 € | 9,87 € |
| District heating | 0,24 € | 5 | 1,20 € | 26 | 6,24 € | 5,04 € |
*per m² and day **per m² Assumption: oil consumption 0.3l*, electricity consumption external heating source 2.9 kWh*, electricity consumption heat pump 1.56 kWh*, district heating 1.56 kWh*, oil: 2 €/l and 2.92 kg CO2/l, electricity: 0.4 €/kWh and 0.42 kg CO2/kWh, district heating: 0.15 €/kWh and 0.19 kg CO2/kWh
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
