High stability and durability, excellent load distribution combined with low weight – these properties make OSB a modern and popular material in interior design. Its environmental footprint also provides compelling reasons for using OSB. The boards are made from renewable timber and store more energy and CO₂ than is used or emitted during the manufacturing process.
Good reasons to use OSB as an installation board for underfloor heating. Although OSB tends to distribute heat rather slowly, the operating principle of thin-layer underfloor heating ensures that even a system using milled OSB installation boards achieves excellent heating performance.
The installation of the thin 10 mm pipes close to the surface, together with the narrow installation spacing, ensures that the majority of the heat is transferred directly to the room via the floor covering. Filling the milled grooves with a filler compound specifically designed for underfloor heating further improves horizontal heat distribution.
Nonetheless, underfloor heating with OSB subfloor panels requires significantly less screed than conventional installation systems. This makes the system lighter, reduces the cost of construction chemicals, and allows the floor covering to be laid after a short drying time. The milled pattern ensures maximum flexibility when laying the pipes. Depending on the condition of the existing floor, the required load-bearing capacity and the requirements for sound insulation and fire protection, the installation can be planned as either a single-layer or multi-layer system.
Like all FLEXIRO kits, the OSB underfloor heating system is connected to existing heating systems via an RTL control box, allowing thermal comfort to be retrofitted room by room.
Technical data for OSB underfloor heating kitHeating capacity and other technical information193 KB
PDF installation instructions – OSB underfloor heatingInstructions with all the necessary information for retrofitting a FLEXIRO underfloor heating system with milled OSB boards.2 MB
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:
| Clip-on rail | Studded panel |
| Most cost-effective, simple installation method | The higher costs are partly offset by the reduced need for levelling compound |
| Tolerates uneven floors | Requires a level and dry substrate |
| Fixed with screws | Fixed using adhesive. In addition, a reinforcement mesh is pre-fitted underneath the studded panels at the factory |
| Medium drying time | Short drying time |
| Installation pattern: Meander | Laying pattern: Maximum flexibility. Spiral laying is also possible. |
| Additional dowel hooks are required for tight bending radii | Secure and even support for the heating pipes close to the surface |
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.
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.
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.
We provide answers to the most important questions about insulating a low profile heating system.
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