Underfloor heating power: what it depends on, how to calculate correctly, drawing up a plan, how much it consumes, heat loss

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Modern systems of underfloor heating entered people's lives not so long ago, but took root immediately. The advantages of this type of heating are felt as soon as you start using them. And, it does not matter if it is an additional heating network or the main one.

But you need to choose the right one characteristic - the power of the warm floor. It is determined by the manufacturer, taking into account the design of the heating element.

The content of the article:

  • Average floor temperature
  • What affects the power of a warm floor
    • Thermal insulation of the room
    • Is it the main source of heating
    • Type of flooring
    • Room type and size
    • Mounting type
    • Type of thermostat
  • How to calculate the power of a water heated floor
    • Planning
    • Area definition
    • Heat loss calculation
    • Coolant consumption
    • Laying step and contour length
    • Floor power
    • Boiler performance
    • Circulation pump
  • Calculate the power of the electric floor heating
    • Which underfloor heating system to choose
    • Determine the temperature in the room
    • How to cut consumption costs

Average floor temperature

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There are several legislative documents that define the so-called acceptable and optimal microclimate indicators. One of them is SanPiN 1.2.3685-21. It indicates that the acceptable indicator is the one at which people already become uncomfortable. But at the same time, there is no harm to health.

Underfloor heating power

The optimal indicator is the one at which comfort is reduced by only 20%. That is, a person does not spend any serious costs on thermoregulation.

The optimal parameter according to GOST has exact temperature limits:

  • minimum - +12 ℃;
  • maximum - +28 ℃.

The exact temperature value depends on two factors: the season and the type of room. The latter is, for example, a bedroom, a living room, a corridor, a bathroom, and so on.

The development of SanPiN was attended by doctors who, knowing human physiology, accurately set the comfortable temperature in living quarters according to the seasonal factor:

  • summer 22-25 ℃;
  • winter 20-22 ℃.

Now for the types of premises:

  • bedroom - 18-20 ℃;
  • living room - 19-21 ℃;
  • for children at night - 18-20 ℃, during the day - 20-23 ℃, for babies not lower than +20 ℃;
  • toilet - 19-21 ℃;
  • bathroom - 24-26 ℃;
  • kitchen - 19-21 ℃, if cooked often, then 17-18 ℃.

Therefore, in each room, the temperature of the warm floor can be different. But there is an average value, which is determined by SNiP, - + 26-27 ℃. At the same time, the indicator is lower than the value of the radiator temperature regime. Hence the savings that they talk about when it comes to a warm field. By the way, Europeans have different standards - + 21-22 ℃.

What affects the power of a warm floor

There are many factors that affect the power of a warm floor:

  1. Climatic conditions of the region.
  2. Is the house insulated or not?
  3. The number of windows in the room.
  4. Warm floors are the main heating system or additional.
  5. The dimensions of the room and its purpose.
  6. Type of flooring.

Everything is clear with the region - the further north, the more power you need to choose underfloor heating.

Do you have underfloor heating in your house?

Yes, completely in the whole apartment / house.


Yes, partially. In some rooms.


No, but I plan to do it during the renovation.


Voted: 1

Thermal insulation of the room

Thermal insulation is more difficult. After all, the main factor influencing the choice of power is the heat loss of the building. The larger they are, the more powerful the heating should be. This means that energy costs will increase, for which you will have to pay more. For example, the walls of a panel house have heat losses in the range of 50%, which is completely unacceptable in modern realities.

Therefore, it is recommended to insulate all building structures of the house or increase their thickness. The first option is both simpler in terms of construction and cheaper. A prerequisite is the installation of insulated entrance doors and multi-chamber plastic or wooden windows.

The number of the latter does not greatly affect heat loss, because this figure is low compared to other elements of the building. It is 10% of the total losses.

Is it the main source of heating

If underfloor heating is the main heating system, then the recommended power for residential premises is 160-200 W per m². If this is an additional system, then 110-140 watts. If an unheated volume is located below, then the indicator increases to 130-160 W per square meter. In damp rooms, the power increases to 160-180 watts.

There is one point that not everyone pays attention to. It is designated in SNiPs. If the area on which it is decided to lay underfloor heating is less than 70% of the total area of ​​the room, then this type of heating system can only be used as an additional one.

For example, if the area occupied by the furniture is 35%, then the power of the heated floor to be laid should be calculated taking into account the above indicated requirement. In numbers - it should not go beyond 110-140 W / m².

Type of flooring

There are difficulties with choosing the power of a warm floor, depending on the material for finishing the floor base. It depends on the thermal conductivity of the lining. For example, for ceramic tiles, this parameter is 0.5-0.9 W / m K. For linoleum - 0.2, for laminate - 0.1.

That is, the larger the value, the more intense the material passes through itself thermal energy and the heating works more efficiently. Accordingly, the power should be less. In this regard, ceramic tiles win, lose laminate.

Room type and size

Specific power, taking into account the types of premises, per 1 m² of area:

  • residential and kitchen, located on the 1st floor of the house - 140-150;
  • residential and kitchen, located on the 2nd floor and above - 120-130;
  • bathrooms and toilets - 140-150;
  • glazed loggias and balconies - 180-190.

All above indicated power values ​​are given without taking into account heat losses. To establish the exact parameter, professionals with special equipment are invited.

Mounting type

Regardless of the type of underfloor heating, it is laid on a prepared base. It should be smooth, repaired, insulated. Another layer is added to the water variety - waterproofing in the form of a membrane laid on the base.

The installation of the heating network itself is carried out according to three technologies:

  1. A ceramic tile is mounted on top of the heating element using an adhesive composition.
  2. A cement-sand screed is poured over the heating element. The thicker the latter, the longer it warms up. Accordingly, for some time there will be an overexpenditure of energy.
  3. dry technology. It is used when finishing the floor base with a laminate. Here it is necessary to understand that the laminate is directly laid on the heating system only if the latter is an infrared film floor. In other cases, a flat solid layer of plywood, OSB or chipboard is installed. There is another cheaper option - laying the heating element in pre-prepared strobes made in the floor.
Mounting type

Type of thermostat

The main characteristic of the thermostat is the switched power, which varies in the range from 3 to 3.5 kW. The exact value can be found in the product data sheet.

This thermostat parameter depends on the power consumption of the underfloor heating. Here it is not specific, but general. That is, the one that is consumed by all square meters.

For example, the total area covered by the heating element is 20 m². Specific power on underfloor heating, it is also passport, 120 W for additional heating, 180 W for the main heat source.

Now you can calculate the total power:

  • 20x120 \u003d 2400 W or 2.4 kW;
  • 20x180 \u003d 360 W or 3.6 kW.

If the selected thermostat has a switching indicator equal to, for example, 3.35 kW, then it can be installed in an underfloor heating system that operates only as an additional heating network.

How to calculate the power of a water heated floor

It is not difficult to calculate the power for warm water floors. To do this, you need to know four indicators:

  • the area on which the heating element is laid;
  • coolant consumption;
  • with what step the heating element is laid;
  • heat loss of the room.


If a water-type or rod infrared floor heating system will be installed in the rooms, then there is no need to draw up a plan. The reason is that plastic pipes and carbon rods easily carry loads from heavy furniture, musical instruments and household floor appliances.

The plan is needed if other varieties are used: cable, cable on mats, infrared film. Therefore, a room is drawn on a sheet of paper on a scale with the exact location of furniture and other heavy objects. Everything that remains free of them should be covered with a heating element.


Area definition

With water and rod options, everything is clear. They will cover the entire floor base with an indent from the walls within 10-15 cm. The other three options will have to tinker. To do this, the plan drawn on paper, or rather the surface free from furniture, must be divided into regular figures. The easiest way is if these are rectangles, the area of ​​\u200b\u200bwhich is equal to the multiplication of their sides. The areas of all the figures are added up, it turns out the area for heating.

You can do the opposite. Calculate the total area of ​​the room. Then separately calculate the area of ​​​​furniture and other items. Sum up the last and subtract the result from the total.

Heat loss calculation

There is a formula by which heat losses are calculated - Q \u003d ST / R, where:

  • S is the area of ​​the room;
  • T is the difference between the internal and external air temperature;
  • R is thermal resistance with the unit m² K/W.

The last characteristic is not thermal conductivity.

This formula calculates the heat loss of building structures: walls, floor, ceiling, windows and doors. Then the obtained values ​​are summed up.

For example:

  • ceiling height - 3 m;
  • room width - 5 m;
  • its length is 10 m;
  • windows measuring 1.5x1.4 m;
  • temperature inside the room +20 ℃, outside -20 ℃.

First you need to calculate the area of ​​\u200b\u200beach building structure:

  • walls: (5+10+5+10)x3=90 m²;
  • floor and ceiling separately: 5x10=50 m²;
  • window: 1.5x1.4 = 2.1 m².

Total area of ​​building structures: 192 m².

The coefficient of thermal expansion is a tabular value. Depends on the thickness of the materials used and their thermal conductivity. For example, floors made of cement screed with a thickness of 10 cm and insulation thickness - mineral wool - 5 cm:

  • R screeds: 0.1/1.75=0.057 m² K/W;
  • R mineral wool: 0.05/0.037=1.35.
  • total R - 1.4 m² K / W.

And in this way all building structures are calculated, the value of which is summarized.

You can calculate the heat losses of each structure separately. Same floors:

Q \u003d 90x40 / 1.4 \u003d 2571 W or 2.57 kW.

The obtained values ​​of heat losses of each building structure are summarized in one indicator.

Coolant consumption

This calculation is carried out only for the water system of underfloor heating. It is made in order to choose the right circulation pump that drives hot water through the hollow pipes of the system.

For this, the formula is used: G=0.86Q/∆t, where:

  • 0.86 - heat capacity of water;
  • Q - thermal power in W;
  • ∆t is the temperature difference in the return and supply circuits.

Laying step and contour length

Here it is necessary to speak only about the water and electric cable warm field. The latter has a wider choice, which depends on the power of the warmest floor per 1 m².

For example:

  • laying step 7.5 cm under the screed, for which a 130 W cable is used;
  • step 12 cm - 150-160 W;
  • step 15 cm - 180-200 watts.

If underfloor heating is used as an additional heating circuit, the output can be reduced. The same reduction can occur if the heating element is placed under ceramic tiles directly on the adhesive.

Pipe is a little different. Here the dependence is not on power, but on the diameter of the pipe. For example, 16 mm:

  • 16 mm pipe diameter is laid in increments of 15 cm;
  • if the heat loss in the room is large, then the step is reduced to 10 cm;
  • you can increase the step to 20 cm if the floor heating is not the main source of heat.

A larger step can be used, but not in houses and apartments. It is used in industrial facilities, laying a pipe with a large diameter.

To calculate the length of the water circuit, the formula F \u003d S / h is used, where:

  • S is the heating area;
  • h is the step of laying the heating element.

If the length of the pipe circuit exceeds 100 m, then it must be divided into several sections with a temperature controller, a temperature sensor and a circulation pump connected to each.

Laying step and contour length

Floor power

This value in water heated floors is not very large. It varies from 40 to 150 W per square meter of surface. But it must be borne in mind that the distribution of the coolant, and, accordingly, heat, must occur evenly throughout the circuit.

There is such an indicator - the density of the thermal water flow. It is he who is taken when choosing a circulation pump. To calculate its value, use this formula Q=q/S, where:

  • q - heat loss;
  • S - heated area.

Boiler performance

It is rare that more than one heating boiler is installed in a house. Therefore, its power is determined taking into account the power of all heating systems, including underfloor heating. That is, for the calculation, the power values ​​​​of each room are taken, which are summarized.

An additional 15% is added to the value obtained. This is a reserve that compensates for the resource costs of the boiler itself, if it operates under the maximum passport load.

You can not carry out complex calculations, but take as a basis the ratio: 10 W of thermal energy is consumed per 1 sq.m of area. For example, if the total area of ​​the house is 100 m², then a 10 kW boiler is used to heat it.

Circulation pump

The longer the contour of the warm floor, the more powerful the pump must be bought. You can use the special formula Q=0.86 P/∆t, where:

  • 0.86 - thermal conductivity of water;
  • P - boiler power in kW;
  • ∆t is the temperature difference in the supply and return circuits.

Calculate the power of the electric floor heating

Before you begin to calculate the electric floor heating, you need to accurately determine several parameters of the heating system:

  1. Warm floor will be used as the main source of heat or as an additional one. That is, its power will be 150-200 W / m² or 110-150 W / m².
  2. What are the heat losses. If they are more than 100 W / m², then it cannot be used as the main one.
  3. Warm floors of the electric type are laid only on an area free from furniture.

The power calculation formula is P=PnS, where:

  • Pn is the power of the heating element;
  • S is the area of ​​the room free from furniture, outdoor appliances and outdoor musical instruments.

The first characteristic is indicated by the manufacturer in the product labeling. For example, the photo below shows that the power of the cable is 24 W / m. It says so - 24W / M.

Calculate the power of the electric floor heating

Knowing the cable laying step, you can determine how much heat it will give out, taking into account 1 m². For example, if the laying step is 15 cm, then 6 contours will be laid in one square meter. This means that the total power is 24x6 \u003d 144 W / m².

Knowing the last parameter and the heated area, you can accurately calculate the total required power of the electric floor heating. That is, multiplying the two characteristics together.

Which underfloor heating system to choose

If we talk about apartments, then there are only heated floors of the electric type. It is forbidden to connect the water system to the heating of the house. You can install a separate boiler or mount a complex water distribution unit. But all this is difficult, unprofitable and time-consuming. Therefore, only electric type.

Any of the above can be installed in a private house. It is better to give preference to water, because it is simply connected to the heating boiler through the coolant distributor.

Determine the temperature in the room

According to the standards, it is necessary to measure the temperature in the room at six points. Height 20 cm and 150 cm from the floor. Horizontally - in two opposite corners and in the middle of the room. Measurements are carried out for 10 minutes at each point.

The average value of three measurements at the level of 20 cm is determined, and exactly the same at the level of 150 cm. In the first case, the temperature should be within +27 ℃, in the second, not lower than +18 ℃.

How to cut consumption costs

Reduce electricity consumption can. To do this, you will have to do several important things:

  1. Conduct insulation of all building structures, accurately selecting the heat-insulating material, taking into account its thickness or thermal conductivity.
  2. Install windows and doors that are insulated.
  3. Use materials with high thermal conductivity for finishing the floor base.
  4. Correctly set the temperature on the thermostats, taking into account the time of day.
  5. Connect a double tariff to the house, which allows you to use electricity at night with a halved payment.

If a decision is made to install underfloor heating in a house or apartment, it is necessary first of all to calculate their power. If this is not done or the choice is made “by eye”, then there is a high probability that energy will be wasted. Plus - the microclimate in the rooms will not be comfortable.

How much does a warm floor consume. Electricity consumption of underfloor heating: video.

If someone already had the experience of choosing a warm floor in terms of power, tell us about it in the comments. Save the material in bookmarks so as not to lose useful calculation formulas.

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