Underfloor heating step by step

Benefits of the underfloor heating:

  • The heat from heating systems is released uniform
  • A pleasant aesthetics (without radiators)
  • A 40% lower consumption than a traditional system
  • A more natural and therefore healthier for the human body heat, because the heat penetrate the body from the feet up, yielding an optimal temperature distribution
  • It does not raise the dust (the dust rises only to a flow temperature greater than 45°C)
  • For ambient temperatures 22-24°C inside the flow water temperature needed is only 35 – 40°C

1. For any house new or old it is important to be well insulated. Both walls and windows (qualitative, with high insulation characteristics) and roof. Insulating the roof should be treated with the utmost importance because it loses the greatest amount of heat.

2. For a new building it is advisable to know from the beginning what kind of underfloor heating is desired to calculate the correct dimensions of doors, windows and staircases.

3. The calculation of these dimensions is very easy: the height dips of doors, windows and stairs (at ground floor) is calculated by adding 13 cm. These 13 cm are composed of anti condens pvc foil + 3 cm of extruded polystyrene (or thicker it depends if you put polystyrene under the floor slab) + plates with grooves for the floors of 2.3 cm (it can put without this plate, on drawn foil or wire netting) + underfloor heating pipe 1.7 cm + over pipe 4.5 cm of screed (cement + sand + water + additive) + 1.5 cm final finish (tiles or parquet). The screed thickness of 4.5 is optimal to dress the pipe heating system through the underfloor. If the screed thickness exceeds 4.5 cm it is not a problem, because up to 7 cm of screed the system works but it will warm hard to start for heat to homogenise.

So increasing the concrete slab is equal to 3 cm of polystyrene + 2.3 cm board + 1.7 cm pipe + 4.5 cm screed + 1.5 finish (tiles or parquet) resulting 13 cm.

Upstairs, eliminating the 3 cm of polystyrene, is reached 10 cm.

4. Before installing underfloor heating should be finalized hot and cold water distribution in plumbing. We must take into account the dimension of underfloor heating discussed above. It is calculated the dimension of the underfloor heating in sanitary items. Should avoid siphons from floor if through them do not pass a washbasin, otherwise water from hydraulic guard can bring to bad odors. The place of water pipes and leaks should be more perimeter (on the edges of the plumbing) to make as much space for the heating plant in floor.

5. It should be established the distributor / manager place of underfloor heating, preferably in a central area. Then is positioned the columns for underfloor heating. The height of a distributor is 60 cm at final height (parquet or tiles).

6. The length of the box depends on the temperature control kit, in the sense that it is attached to a distributor or not. Fitting boxes recessed in wall are the following lengths: 555 mm, 785 mm, 950 mm, 1250 mm. Below is a table with dimensions on length, with or without distributor.

7. It is positioned wires for the system automation. We need a voltage of 220 v and cable of 3 x 1.5 mm in the distributor box.

8. Are established the areas where we want to program or adjust the temperature (or do nothing if you want a single temperature). Usually the halls are coupled with baths; the bedrooms with bathroom and dressing rooms; other bedrooms together; living separate; kitchen with the living room (if they are in common areas). Note that if the open areas are meeting it is mounted and a thermostat. It is positioned away from sunlight or wetlands, in a neutral zone.

9. It is calculated the number and thickness of wires that needs thermostat affiliated with automation unit that command the actuators.

10. The wires to the thermostat is positioned to the distributor that connects the fields to floor related area that we want to order / adjust. In brief – a thermostat per distributor per controlled (adjustable) area.

11. It notes the wires arriving in distributor from where we pulled every wire (so we know how to tie the automation).

12. The house is plastered.

13. After plastering the house, remove the excess of the material from the floor and clean the dust.

14. On the concrete slab spans the PVC foil, bending edges of 5 cm to prevent condensation.

15. It is mounted the perimeter band from right to left, with cut side up (for guidance, with writing up) with foil to the inside room. It is unglued only adhesive tape from wall, and not that of the foil. Attention! Do not spend perimeter tape ends but apply them one after the other.

16. Mount the polystyrene (3 – 5 cm). Cut the places where pipes / columns / current will pass. Where are many passages with pipes do not cut the polystyrene into small strips rather fix them with screed or adhesive.

17. Mount plate with grooves (I recommend Taker plate). Try to keep the lines or steps, that they be from 5 to 5 cm.

18. Calculate the heat demand.

19. The heat demand (number of watts required per level) is equal sq x the height of the level x 35 watt/mc (if the insulation is made with polystyrene of 10 cm and windows are of good quality). If we want to know the power plant required for heating, divide the necessary of heat to 1000 watts. Remember that this is an empirical calculation, covering, the calculation itself is more laborious and requires taking into account several aspects.

20. How much heat we can produce with underfloor heating system? Here’s a pocket calculation (simplistic):
For tiles, marble, travertine, etc., at step 20 cm between the pipes the result is 100 watt / sq.m. At step 15 cm between the pipes the result is 120-130 watts/sq.m and at step 5 cm between the pipes are obtained 150-160 watts/sq.m. For parquet with thickness up to 14 mm (triple stratified), at step 15 cm between the pipes we get 60-70 watts/sq.m, at step 10 cm between the pipes 90 watts/sq.m and at step 5 cm between the pipes the result is 100 – 110 watts/sq.m.

21. It is calculated the necessary length of pipe depending on the choice of the final finish or zone (parquet or tiles; garage or viewing area). After the calculation of the necessary of pipe for that level it will be able to know the type of the distributor needed.

22. There are 4 types of areas for which is calculated the total length of the pipe:
Garage – step of 20 cm between the pipes is 5 ml/sq. m. Eg: 23 sq. m x 5 = 115 ml of pipe.
Viewing area – windows to the floor level, with HP = 0. If the doors have a wide open, we are interested in their length. In this case is as follows: the length of the zone (in front of the window) x 1 m width, at step 5 cm that is 20 ml/sq.m. Eg: if a glass with HP =0 has 3.3 m then 3.3 sq. m x 20 ml = 66 ml. Thus we produce a hot air barrier (natural convection), so the glass does not sweat and condensation does not occur. Be careful do not forget to remove these areas from the total area, so you get an accurate result.
Tiled area, marble or other materials based on lime and other derivatives – at step 15 cm are obtained 7 ml/sq. m. Usually for toilets is using a 10 cm step because the surfaces are small and we can adjust the general heat demand.
The parquet area (with thickness up to 14 mm, triple stratified) at step 10 cm between the pipes is obtained 10 ml/sq. m.
Some aspects related to the flooring installation – It must be approved by the manufacturer for such a work, it must have a good thermal resistance (specified by the manufacturer) and usually is used the double layered with slats, case in which the heat uses only 3-4 mm of noble wood. The parquet sticks to screed with a special elastic adhesive, the screed must first be properly dry, at low temperature by turning the heat. The screed has to reach the optimal values of moisture approved by the flooring manufacturer. After which the screed dried it is indicated that the parquet slats to be stretched on it and allowed to dry up at 8°C, thus avoiding the parquet to work very hard (not to deform). Many professionals in installing the parquet apply an epoxy resin over screed to prevent the moisture infiltration. If the screed is well dry it is not necessarily to be applied the resin.

23. Here’s a concrete example for calculating the necessary of the pipe for one level: tiles 30 sq. m = 210 ml, parquet 60 sq. m = 600 ml of pipe and 12 ml (12 sq. m of viewing area) = = 240 ml. For 23 sq. m of garage = 115 ml. Thus result a total of 1165 ml of pipe required for this level (eg: ground floor).

24. After calculating the total length of pipe it is calculated the number of circuits necessary for that level. Eg: divide the 1165 ml of pipe to 95 ml/circuit = 12.26 circuits, so it will mount a distributor of 12 circuits with a box of 1250 cm width (in case of the existence of a temperature reduction kit) or a boc with 950 cm width if you do not want a temperature reduction kit.

25. It is important to check the technical data of temperature reduction kit to find out whether it matches with the surface on which the system will be installed. It should be checked and the number of square meters which the kit supports them. If the information does not correspond it will mount a pumping group with tub with 3 way with a more powerful pump. So in this case it is better to consult a specialist. Note that a pump of 25/6 does not lead more than 80 sq. m. The next model is 25/7 and leads between 120-150 sq. m.
Attention – if the temperature adjustment kit is installed in room service at distance of distributor it is indicated to increase the heating pipe diameter columns. For a distributor of 12 circuits it is using a 28 mm copper pipe or its equivalent in other materials. Thus the flow of hot water is optimal for all the circuits.

26. If there is a gas boiler it can be mounted a loss header on central, proper size with it and it can put a pump (with specifications of calculation results) thereby eliminating 3-way valve. If the circulation pumps are mounted in technical room it is necessary to pose a cable 2 x 1.5 from automation distributor pump. So the automation will interfere with the pump phase and it will start and stop at order of the automation.

27. In conclusion, for a distributor of 12 circuits are necessary 24 eurocon connections of 17 x 3/4, and 24 curved wire of 17 if the level is perfect. For larger areas it is preferred a stronger kit with temperature control that will not fit in the box distributor and will be mounted in the equipment room. In this case the box will remain 950 cm width.

28. The foil remaining on perimeter band will stick on plate with grooves such that not be too stretched or do not remove the perimeter band from the plastered wall.

29. Having all the calculations for pipes and the required number of circuits you can start laying the pipe on plate with grooves, considering the calculations made.

30. It’s good to have an unwinding of the pipe to be able to maneuver coils of 600 ml, thus preventing large losses of pipes (heads). Thus the pipe will run properly on the floor it will not twist or it will not quit the clamps / grooves. It is advisable to calculate the amount of pipe to know how many circuits will make from the coil.

31. For a home it is recommended a serpentine variant of worm type. It should be realized measurements to fit in the calculated values and it is indicated to not exceed 120 ml of pipe/circuit to not be necessary more powerful circulation pump (additional cost). The average value for a circuit field is 95 ml, after leaving the distributor and to return to it. It is indicated circuits to be calculated such that be as equal but it is not necessarily a serious problem if in certain situations a circuit is 115 ml and another 40 ml. In such situations using flow flowmeters, with indicators with which we can adjust the flow of water on each circuit. An optimal value is around 1.5- 2.5 l / m.

32. Next is pressure test – hold the circuit for 17-30 minutes at 9 bar, then lower the pressure of 6 bar during the screed pouring. After pouring and drying of the screed (2 days) the pressure may be lowered to 3 bar.

33. For a correct screed it will perform a calculation of necessary additive. This additive should be introduced in the composition of the screed and it is delivered in the underfloor heating package. The calculation is as follows: at a screed of 6 cm (including pipe) is required 400 grams of additive per sq. m of poured screed. It is advisable to read the instructions printed on the can of additive.

34. After finishing the screed it can start the drying process. Do not mount anything on the screed surface until it is completely dry. It begins with a pipe temperature of 15°C for 5 days, then it can rise by 5°C per week. The expertise of the specialist in flooring can tell when it has reached the optimal level of moisture and when it can start installing the parquet.

35. It is indicated that on the distributor box to write how many ml has each circuit and where they came from.

36. It connects automation according to drawings received. Note that a thermostat can order one or more actuator for the circuits affiliated to the thermostat area. Do not forget to pass to the pump phase (+) through automation (so the phase interrupts). The neutral and grounding binds directly to the current pump circuit.

Following these indications it will ensure a properly executed underfloor heating which will operate at maximum efficiency.

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