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Born more than 50 years ago, heated floors have evolved greatly. Today very powerful, they are declined in electric version or with water and settle as well in the nine as in renovation.

Heated floor with water.

The heated floors were developed in the 1960s for collective housing. They were hydraulic systems consisting of large tubes embedded in a ravoirage surmounting the slab of the floor. They were fairly spaced and had to receive very hot water to heat the dwelling, with the result that the floor temperature was too high to be comfortable and impossible to adjust individually.

Low temperature floor heating (PCBT)

It's towards the late 1970s that the first low-temperature heating floors (PCBT) were designed. They have not only a custom regulation but also smaller tubes (Ø 14 to 20 mm) and more numerous. Dried in a slab or screed, they are sometimes made of copper and much more often based on crosslinked polyethylene. Depending on the type of support (flat slab, stud or grooved), the tubes are stapled with jumpers or held by the studs or grooves. In the latter case, the device is not covered with a coating coating (wet), but with a dry screed (6 mm thick cement-cellulose plates).
PCBT has the particularity of being powered from collectors (brass nurseries) located at the bottom of the walls, on each floor or in each room. They serve on the one hand to connect the tube loops and on the other hand, to modulate the flow rate. The tubes convey much less hot water than their predecessors, without losing comfort.
The floor does not heat the air (like a convector) but does radiate heat to the walls and furniture of the room. They thus participate in maintaining a homogeneous ambient temperature, including in high ceiling rooms. This is the advantage of so-called reversible heating floors that can also be used to cool the temperature of a dwelling in the summer by 2 to 3° C. Everything depends on the device that supplies the floor: boiler or solar collectors provide only hot water, but a heat pump (reversible) or a geothermal probe can deliver fresh water.

Eight terms to know
• BAO: oxygen barrier (avoids the risk of sludging and prolongs the life of the tubes)
• FEP: perfluoro-ethylenepropylene (formerly PFEP)
• PER: crosslinked polyethylene
• PE-RT: polyethylene resistant to temperature
• PIR: derived from polyurethane
• EPS: expanded polystyrene (HD: high density)
• PSEX: extruded polystyrene
• PU: polyurethane

Collector for underfloor heating.

The collector for underfloor heating must be installed as close as possible to the parts being dispensed in order to minimize the length of the pipes.

Electric radiant floor (PRE)

Variant of PCBT, the electric radiant floor (ERP) uses heating cablesin most cases in the form of frames 50 to 85 cm wide and 1.70 to 30 m long. Powered by a "cold link" consisting of two conductive cores and a ground wire, the cables take place on a synthetic mesh according to a step (space between the cables) from 13 to 25 cm. Defined according to the losses calculated in the part, the pitch makes it possible to be in conformity with the pfd values ​​not to be exceeded. The frames are stapled on a insulating plastic honeycomb or sometimes based on mineral wool (only for the purpose of laying a bonded floor). Insulation and frames are covered with a conductive screed based on mortar or concrete (Ø granulate <8 mm). Army of a welded wire meshit is she who broadcasts the infrared radiation emitted by the electric cables. The system is slaved to a thermostatic control room by room which offers customized operating ranges. Note that the smaller the piece to be equipped, the more the price of a PRE at the m2 is high.
The installation and connection of a PRE must be carried out in accordance with the provisions of the standard NF C 15-100 (available on The metal shielding cables must be earthed; just like the reinforcement mesh of the slab. In wet rooms, this mesh must also be connected to the local equipotential bonding. Finally, the installation must have a 500 mA differential protection.

Electric heated floor.

The electric or water heating floor installs imperatively on an insulator. The thickness of the latter depends on the quality of the soil, but also the room concerned: is it located above a heated room (kitchen, living room...) or unheated (crawl space, garage...)?

Wrapping cables: the points to know

The coating of the cables or tubes must be carried out using a mortar or concrete capable of receiving a bonded or sealed floor covering. Its thickness is less than or equal to 5 cm and its density higher than 1.7 t / m3. of the splitting joints are expected every 40 m² or at most every 8 m. The armatures - chosen according to the thickness of the screed or slab and the nature of the thermal insulation chosen - must be put in place so as to be coated and not to touch the heating elements. In wet rooms, the armature is connected to the equipotential bonding. No pipe or sheath should be embedded in this structure. Finally, the risers crossing the slab must be protected by sleeves.

The criteria for choosing the right heating floor

The step of screening

The pitch of electric heating floors is the distance between the turns formed by the cables or the tubes: the more the pitch is reduced, the more the pfd increases and the heat delivered homogeneous. The models with reduced pitch are the most comfortable.
Fixed by the regulations, the pfd can not, however, exceed 85 W / m2. It may, however, be increased by 25% (106 W / m)2) when the underfloor heating is regulated by a room thermostat NF category B or NF EN 60730.
When laying, you must respect a minimum distance between the electric frame and the following elements: 3 cm a pipe crossing vertically; 10 cm a wall or partition; 20 cm a masonry sheath, the wall of a partitioned or masonry staircase or the outer wall of a flue; 40 cm from the edge of the footprint of the fireplace, stove, insert...

Insulation and thickness

Insulation is essential to the durability and efficiency of the structure. With its low thermal conductivity, the expanded polystyrene is a very good thermal insulator. Its acoustic performance is also excellent. The polyurethane resists moisture, the extruded polystyrene (XPS) compression and shock. The polyisocyanurate
(PIR) takes all these advantages and incorporates biobased elements.
The hydraulic heated floors often exceed 10 or 15 cm (insulation + screed + coating). The thermal resistance of the insulation must be at least R = 0.75 m2.K / W on heated ground and 2.1 m2.K / W on basement, cellar or crawl space (1 and 2.2 for a PRE). The choice of insulation of less than 45 mm is advised in renovation. It must be ensured that the thickness of the assembly does not reduce the ceiling height too much (2.40 m minimum from the finished floor).

Coatings compatible with a heated floor

Lay a laminate floor on a heated floor.

Before the progressive commissioning of a floor heating, it is imperative to wait two weeks in order to avoid any risk of cracking of the screed.
Floor covering must be as conductive as possible (thermal resistance R <0.15 m2.K / W). That's why we meet so often with sealed mineral materials: ceramic tiles, slabs or mosaics in limestone, marble, granite... laminate floors and the multilayer parquets are possible on a floor heating water or electric provided not to be too thick (less than 15 mm for a floor) and to have a CSTB Technical Opinion * authorizing it for this type of job. Same thing for textile or plastic coatings whether they are floating or glued on the support.
* Scientific and Technical Center for Building

4 electric heated floors

Electric heated floor.

Finimetal - Cosymat

  • Step: 19.5 cm
  • Weft width: 50 and 80 cm
  • Weft length: from 3 to 10 m (50 cm); from 7.5 to 32.5 m (80 cm)
  • Power: from 150 to 2600 W
  • Inner envelope cable: PVC
  • Ext. of cable: PER
  • Fixing: by riders
  • Insulating support: Grooved PIR slotted interlocking slabs
  • Coating: mortar screed
  • Price: from 27 € / m2

The +: the price

Electric heated floor.

Thermor - KS

  • Step: 17 cm
  • Weft width: 60 and 85 cm
  • Weft length: 2.4 to 8.7 m (60 cm); from 1,7 to 28,6 m (85 cm)
  • Power: from 150 to 2600 W
  • Inner envelope of cable: FEP + PER
  • Cable outer cover: PVC
  • Fixing: by riders
  • Insulating support: not supplied
  • Coating: concrete slab or mortar screed
  • Price: from 35 € / m2
The +: pretram on plastic lattice

Electric heated floor.

Atlantic - Domocable

  • Step: 17 cm
  • Weft width: 60 and 85 cm
  • Weft length: 2.4 to 8.7 m (60 cm); from 1,7 to 28,6 m (85 cm)
  • Power: from 150 to 2600 W
  • Inner envelope of cable: PER
  • Ext. cable: PVC
  • Fixing: by riders
  • Insulating support: not supplied
  • Coating: fluid screed, mortar screed, concrete slab
  • Price: from 36 € / m2
The +: handy and easy to cut

Electric heated floor.

Deléage - Infracable

  • Step: 16 cm
  • Width of frame: 85 cm
  • Frame length: from 1.76 to 26.1 m
  • Power: 150 to 2400 W
  • Inner cable cover: PER
  • Ext. cable: PVC
  • Fixing: by riders
  • Insulating support: not supplied
  • Coating: conductive screed or fluid screed, tiled or sealed tile mortar
  • Price: from 48 € / m2
The +: its reduced dithering

4 heated floors with water

Heated floor with water.

Rotex (Daikin) - Monopex

  • Thickness: 35 mm
  • Dimensions: 1 x 2 m
  • Tubes: PER Ø from 14 to 17 mm
  • Fixing: by riders
  • Insulating support: smooth and self-locking PSE slabs
  • Coating: floating dry screed
  • Price: from 42 € / m2
The +: exists in rolls of 10 m

Heated floor with water.

Comap - Exact Biofloor

  • From 25 to 120 mm
  • Dimensions: 1.20 x 1 m
  • Tubes: PER Ø from 14 to 20 mm
  • Fixing: by riders
  • Insulating support: Grooved-grooved PU slabs on four sides with interlocking
  • Coating: floating dry screed
  • Price: from 48 € / m2
The +: the grid for cutting

Heated floor with water.

Schlüter - Bekotec EN

  • Thickness: 23 mm
  • Dimensions: 0.90 x 1.20 m
  • Tubes: PE-RT Ø 14 mm
  • Fixing: by interlocking between the studs
  • Insulating support: self-adhesive EPS slabs
  • Coating: floating dry screed
  • Price: from 48 € / m2
The +: reduced thickness of screed (8 mm above the studs)

Heated floor with water.

Uponor - Siccus FX

  • Thickness: 30 mm
  • Dimensions: 0.80 x 1.20 m
  • Tubes: PE-Xa BAO Ø 16 mm
  • Fixing: by grooves
  • Insulating support: interlocking PSE slabs
  • Coating: floating dry screed
  • Price: from 55 € / m2
The +: immediate circulation after the first heating

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