An important indicator taken into account when installing a warm floor is the amount of energy consumed. Thanks to the installation of such a system, energy costs for heating the premises are reduced by about 15%. Warm air rises upwards, so when using a radiator for heating, more energy is needed to warm it up below. With a warm floor, this problem does not arise. To accurately determine the amount of energy consumed, first calculate the total power of the underfloor heating, and then the specific power of the heating equipment, which is determined in watts per square meter.
Required data for calculation
Significantly affect the calculations of the features of the room. If it is poorly insulated, unheated rooms or external walls with two or more windows adjoin it, the energy consumption for heating the room will be higher, so the power of the heated floor should be higher. However, in simplified calculations, only the area of the room is taken into account, although in this case it is more correct to take into account not the area, but the volume. The result of a simple calculation will be close to reality if the ceiling height in the room is approximately 2.7 m. If the ceilings are high, the system power, other things being equal, should be higher, since more energy is required to heat a larger volume of air. Then a correction factor must be included in the calculations.
The type of underfloor heating also has some influence on the calculation, since the power of different types of heaters per square meter differs. Heat transfer largely depends on the thermal conductivity of the floor covering: tiles, self-leveling floors are optimally suited for installation. Wood conducts heat poorly; it is not recommended to install such a system under wooden floors.
If the floor is to be used as the main heating medium, its power should be 180-200 W / m2, if as an additional one - 100-160 W / m2, provided that the system is laid over the entire area.
The area on which the furniture is installed or dense carpets are laid are not taken into account in the calculations, since the manufacturer does not recommend laying underfloor heating in these areas.
An important feature: be sure to take into account the possibilities of electrical wiring. In older homes, the wiring may not be able to withstand the high power of the system.
Calculation of capacities per square meter
When heating any room in any building, there will be more or less heat loss. To calculate them accurately, you need to take into account the geographical location, the number of storeys of the room, the area of the windows, the material and thickness of the walls, and other parameters. It is convenient to use special calculators for calculations or to resort to simplified calculations.
Let's say the heat loss is calculated in one way or another, then to calculate the total recommended power, you should resort to the formula:
Pud. = Pset. / Sуwhere
- Sу. - the area on which the warm floor will be laid;
- Pust. - the required total capacity of the system;
- Rud. - specific power of the warm floor, i.e. power for 1 m2.
You must first calculate Pust. according to the formula:
Pset = 1.3 × Pp, Where
- Pп - heat loss;
- 1,3 - correction factor, taking into account that the power of the heating elements should be approximately 30% higher than the heat loss.
Suppose that in a room with an area of 17 m2 the heat loss was 2000 W, then Pset. = 1.3×2000 or 2600W.
Let the underfloor heating system be laid on 70% of the area, we calculate 17 * 0.7 = 11.9 m2. This is the area of the warm floor. So, substituting the values into the first formula, we get 2600 / 11.9 = 218 W / m2. This is the power density of the system that is used as the main heat source.
It should be borne in mind that the power density requirements will differ depending on the purpose of the room. These data are indicated in the table reflecting the requirements for the specific power of the underfloor heating used as an additional source of heating (heat losses are compensated by radiator heating).
| Appointment of the room | Average power values, W / m2 |
| Glazed balcony (loggia) | 180 |
| Bedroom | 120-130 |
| Kitchen | 120-130 |
| Living room | 120-130 |
| Children | 140 |
| Bathroom | 140-150 |
| Rooms on the first floors | 140-160 |
If linoleum or laminate is used as a floor covering, the specific power of the warm floor should not exceed 100-130 W / m2.
The required power for heating the room is calculated by the formula Pset = Psp × Sу, so 120×11.9 = 1428 W.
It is recommended to install a warm floor, the power of which is 20-30% higher than the recommended one. The power reserve is necessary for the normal operation of the equipment, since it does not have to constantly work at its limit.
Calculation depending on the types of underfloor heating
Components for underfloor heating devices differ in type, power, length and width. To find the best option taking into account the calculated values, you need to understand the features of each variety.
Electric cable
A single-core or two-core resistive heating cable is used for the system device. It costs less than the rest of the underfloor heating. The cable is laid with coils or a snake, secured with special clamps, and poured on top with a coupler. Do not shorten the resistive cable. Because of this, the resistance changes, the current increases and the entire system setting gets lost.
The thicker the screed, the greater the heat loss. The optimal concrete thickness is about 5 cm, therefore, self-leveling floors are mainly used. Only in some cases, in order to save money, when the night electricity tariff is lower, it is advisable to organize a thick 10-15 cm heat-accumulating screed. At night, it will warm up and during the day it will give off heat to the room.
In those areas where furniture is placed or the floor is covered with a dense fabric, it is impractical to lay a heating cable. This leads to waste of energy, overheating of the cable and damage to furniture, because the resistive conductor heats up evenly. If, for any reason, it is necessary to lay it in areas with poor heat transfer, you need to use a self-regulating option. Its resistance depends on the temperature at the site. However, due to the high cost of this variety, underfloor heating from a self-regulating cable is practically not made. Thus, the power of the underfloor heating should be calculated taking into account only areas free of furniture and carpets.
The heating cable has a linear power of 10 to 60 W per m2 and on average there are 4-5 turns per square meter. In total, the specific power of the cable floor is 120-150 W / m2. If the linear power is not indicated, you can calculate it by dividing the total power of the cable by its length.
When calculating the specific power of the underfloor heating from the heating cable, an important parameter should be taken into account - the laying step. It is calculated using the formula:
h = Sу × 100 / Lkabwhere
- h - laying step;
- Sу - heated area;
- Lkab - length of cable.
The optimal distance between the loops is 7.5–10 cm. With the most dense laying, there is a possibility of self-heating of the electric cables - it will not have time to give off heat. In this case, the service life of the warm floor is reduced.
Thermomat
It is much more convenient to use the cable in the mats than the conventional heating cable. The mats do not need to be fixed, it is enough just to spread them on the floor, make a self-leveling thin screed, put laminate, parquet on top, and lay tiles. Cable underfloor heating in mats will feel great under a layer of tile adhesive.
For the manufacture of thermomats, a two-core resistive cable is usually used, so you cannot cut the mat along the conductors. Only the polymer mesh on which it is attached can be cut. The specific power of the thermomat is 100-150 W / m2, much less often 200 W / m2. If the system is to be used as an additional one, it is enough to take the specific power values from the table above, in accordance with the type of room, and select a thermomat of a suitable power.
Infrared film
Infrared film is made from carbon. It is very thin and can be installed under almost any floor covering. Features of infrared film in principle of action: infrared radiation heats not air, but objects. Also, the film floor has a high efficiency - it reaches 95%. It is necessary to lay such a floor in a dry way, making sure that there is a gap of 20 cm from the edges of the film and walls (pieces of furniture). You can cut the film not anywhere, but usually only every 25 cm.
The specific power of such a system varies from 130 to 230 W / m2. To accurately calculate the required value, you will need a scaled floor plan, made on graph paper, with an exact plan for the layout of the film. The laying area is calculated from it. For example, it is equal, taking into account the necessary indents - 10 m2 (total area - 17 m2). You need to calculate the percentage of the total area of the room: Sу × 100% / Stot... It turns out 10 × 100/17 = 58.8%. If the area is less than 60%, then an IR film with a specific power of 220 W / m2 is chosen, if more than 60%, then from 160 to 220 W / m2. If necessary, calculate Pset by the formula Pset = Psp × Sу or for a specific example 220 x 10 = 2200 watts.
Power consumption reduction options
The financial costs of heating a room when using a floor heating system can be significant. There are several ways to reduce power consumption and save money:
- The house or apartment must be properly insulated. If the heat losses are insignificant, it will be possible to save 35-40% of energy, thanks to this, financial costs will be reduced by the same amount.
- About 30% of electricity can be saved by installing a thermostat at the coldest point in the room. The system will automatically turn on and off when the set threshold is exceeded or the temperature drops below the set value.
- In some regions, different tariffs have been introduced for day and night consumption of electricity. In this case, it is recommended to install a two-tariff or three-tariff meter, install a cable floor, fill in a thick heat-accumulating concrete screed and turn on the warm floor at night.
- Underfloor heating should be laid only on areas free from furniture. Installation under carpets and furniture harms the system itself and leads to waste of thermal energy.
By lowering the room temperature by one degree, you can save about 5% of the total cost.
The underfloor heating system allows you to create the most comfortable indoor climate. But before you buy a cable, mats or IR film, you need to calculate the required power of the warm floor per square meter. The features of the material are such that it is impossible to simply take and cut off the excess cable or film.
