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Both installation methods allow for the safe and rapid installation of a low-profile underfloor heating system. Whether installing using clip rails or studded panels, it is essential to ensure that the subfloor has sufficient load-bearing capacity beforehand.

Clip rails are screwed to the subfloor and can accommodate unevenness, such as that found in wooden floors. Studded panels allow for flexible installation patterns and reduce the need for levelling compound. Here are the specific advantages of the installation methods in detail:

The maximum permissible length of the heating circuit in water-based surface heating systems is largely determined by the fluid dynamics of the pipework. As the length of the pipework increases, the pressure drop caused by frictional resistance rises continuously. This pressure loss depends on the internal pipe diameter, pipe material, surface roughness, flow rate, and the temperature and viscosity of the heating medium.

Particularly in the case of small-diameter heating pipes, such as PE-RT pipes with an external diameter of 10 mm, comparatively high specific pressure losses occur due to the reduced hydraulic cross-section. If, in addition, a higher flow rate is required due to high heating loads, the pressure loss increases disproportionately. At a flow rate of 86 l/h, the specific pressure loss of a 10 mm PE-RT heating pipe is typically around 7–8 mbar/m (R).

For a heating circuit with a pipe length of 50 m, this results in:

Δp≈7.5 mbar⋅50 m≈375 mbar

In addition to the pipe length laid in the heating surface area, all supply and return pipes must be taken into account hydraulically, as these also contribute to increasing the total resistance.

In the case of heating circuits operating in parallel within a heating circuit manifold, the hydraulically most unfavourable or longest heating circuit always determines the required head of the circulation pump. For this reason, the individual heating circuits should be designed to have pipe lengths that are as uniform as possible. To ensure uniform heat distribution and defined flow rates, hydraulic balancing in accordance with accepted engineering practice is also required.

To ensure reliable operation within a wide variety of system configurations whilst meeting the requirements for energy efficiency, hydraulic stability and standard-compliant system operation, the maximum recommended heating circuit length for FLEXIRO systems is limited to 50 m. This design takes into account typical operating conditions of modern low-temperature surface heating systems and enables operation with standard high-efficiency circulation pumps without impermissibly high pressure losses or flow velocities.

Under favourable hydraulic conditions — for example, with powerful high-efficiency pumps, low system temperature differentials or reduced flow rates — the technically feasible heating circuit length may be slightly exceeded in individual cases. However, the maximum permissible pressure losses, the pump design, and the requirements for hydraulic balancing and uniform heat distribution must always be taken into account.

The function of heat distribution plates is clear from their name. Thanks to the excellent thermal conductivity of the materials used – usually aluminium or galvanised steel – the plates transfer heat from the heating pipes to the floor surface. This ensures even heat distribution and minimises thermal bridges between the pipes. The use of heat conduction plates increases the energy efficiency and response speed of the underfloor heating system. The required thermal comfort is achieved at a lower heating water temperature, which offers further energy benefits, particularly when used in conjunction with heat pumps.

Heat conduction plates are mostly installed in combination with dry-build systems, as the materials used here, such as gypsum fibre, polystyrene or wood, have lower thermal conductivity compared to wet screed. In standard wet screed systems using screed concrete or cement screed as the casting compound, heat conduction plates are rarely used, as the concrete handles the heat distribution.

Heat conduction plates are also unnecessary for low profile underfloor heating systems, as the thin pipes used here can be laid at close intervals. Furthermore, laying the pipes close to the surface ensures direct heat transfer into the room via the floor covering.

These are the reasons why the thin-bed heating system is effective even without heat-conducting plates

Wet installation

Our 10 mm systems use special studded panels or clip rails to secure the pipes. This ensures that the heat-carrying pipes are fully enclosed by levelling compound. The levelling compound acts as a heat-conducting layer and ensures heat transfer directly to the floor covering. For these reasons, we also recommend using a levelling compound specifically designed for underfloor heating systems to embed the pipes in our OSB and dry screed systems.

Tight installation spacing

Due to the flexibility of the thin PE-RT pipes, which allow for small bending radii, they can be laid at tight intervals of 10 cm or less. As a result, the temperature difference at the floor surface between two pipes is so small that no metal plates are required for the cross-distribution of heat

Potential air pockets

Heat-conducting sheets can be problematic in very thin floor constructions. If the pipe does not fit perfectly within the sheet, insulating air pockets can develop, which have a negative impact on heating performance. In thin-layer systems, the direct bond between the pipe and the grouting compound is crucial for stability and heat conduction.

Acoustic risks

If heat-conducting plates are not absolutely firmly bonded to the pipe, they can expand when heated and cause noise (cracking).

 

If you have any project-related questions regarding the use of heat conductive plates, please feel free to contact our technical support team.

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The straight or angled connectors for quick and secure connection of two pipe ends can be easily loosened again. To do this, turn one side of the connector anticlockwise and hold the collet clamp pressed down while pulling it off. The connector can now be easily removed from the PE-RT pipe.

The exact procedure is shown in the manufacturer's video:

• https://www.youtube.com/watch?v=mpjG-BdLHLI

We are often asked how much it costs to retrofit underfloor heating per square metre. Before answering this question, we first enquire about the initial situation. How many rooms are to be retrofitted? How large are the heating surfaces? What is the condition of the floor? When was the house built? Is there thermal insulation? Is there a heating load calculation? Can the installation be carried out by the customer?

With the information on the initial conditions, we can suggest a suitable underfloor heating system and thus specify the costs for the heating technology.

However, the costs for retrofitting underfloor heating also include the costs of installation, the expenses for construction chemicals and, if necessary, for the disposal of the old floor. Our tips on cost calculation explain exactly which cost items need to be taken into account here.

Typical costs for underfloor heating

The Multibox 4K-RTL for connecting a retrofitted underfloor heating system to the existing heating system has a flow shut-off valve in addition to the RTL valve. The flow shut-off valve is particularly useful when individual heating surfaces need to be serviced or repaired. In these cases, the water does not have to be removed from the entire heating system. It is sufficient to drain the affected heating area.

In addition, the Multibox housing is dimensioned so that even the quadruple distributors for connecting up to 4 heating circuits fit comfortably in the flush-mounted box. They are covered by the housing and protected from direct contact with building chemicals.

All features of the Multibox 4K-RTL