The use of underfloor heating as the main or additional source of heating for a house or apartment is a popular “innovation” that has come to our country relatively recently. Compared to traditional methods, this heating method is more efficient and economical.
But, in order for such a system to work “like clockwork”, with maximum heat transfer, before installation, it is important to make a competent calculation of the heat of a warm floor, taking into account the peculiarities of its structure and functioning.
The design of the warm water floor system
Water type floors have a fairly simple design. In simple terms, they are concrete slabs, with a heating element inside, the function of which is performed by pipes filled with hot water. The coolant enters the pipeline from the distribution of the main heating system and, after passing through the full cycle, returns back. That is, we can conditionally say that a warm floor is the same heating radiator, only of a horizontal type, mounted on the basis of the room and protected from loads and damage during operation with a concrete screed.
Such a system consists of several layers following one after another.. It:
- Basepreviously leveled and prepared accordingly.
- Waterproofing pasting or coating type. In the first case, its function is performed by materials based on bitumen with polymer additives, reinforced with fiberglass or polyester. The second group is represented by mastics of bitumen-rubber, bitumen-polymer or cement-polymer type.
- Thermal insulation layer. To create it, foam or EPS (extruded polystyrene foam) is used. The thickness of this “layer” is determined by the calculation method.
- Roll insulation with a reflective surface (shielding substrate).
- Pipesincluded in the underfloor heating system.
- Concrete screedmade with the addition of a plasticizing compound and additionally reinforced with a reinforced mesh with cells of 100 x 100 mm, from a wire with a cross section of 3–4 mm.
- Finish flooring.
It operates as follows:
- Through the pressure pipe, the coolant (water), heated to the optimum temperature, enters the underfloor heating circuit.
- Having passed through the pipeline system, it transfers its heat to the screed, heating it to a temperature of approximately 27–36 C⁰.
- The cooled water moves to the return line, through which it flows into the boiler, where it is heated again.
That is, in fact, one of the main elements of the heating structure is thermal insulation.. Accordingly, when calculating a warm water floor, it is necessary to choose its thickness correctly.
For “cold bases” located above an unheated basement or soil, it should be at least 50 mm with a heat insulator density of 25 kg / m³.
Data required for the design of underfloor heating devices:
- Apartment plan or houses (with all floors).
- Information about type and composition of walls, windows and doors.
- Instructions regarding temperature regimeplanned indoors.
- Information about the place of installation of the heating boiler and its location relative to the floor level.
- Number of outlets and risers inside the house.
Based on these indicators, the calculation of heating with warm floors is made. First of all, for this a project plan is being drawn upwhich includes the following information:
- Number of heating radiatorsconnected to the system, their type and location.
- Scheme of the future location of the pipeline with pipe diameters and lengths of straight sections.
- Pipe layout indicating the distances between them and the temperature of the coolant (these two points can be combined).
- Radiator power dataincluded in the system.
- Setting Information its automatic part.
After drawing up a plan and project of the heating system, the power of the warm floor is calculated. This figure will depend on the following factors:
- Area and type of heated room.
- Features of its design and the nature of future operation.
According to these indicators, you need to select heat source power. It is calculated using the following formula:
Mn = 1.2 * Qwherein
MP is the thermal power;
Q – heat loss during operation;
1.2 — safety factor, varying from 1 to 1.2 units.
That is, in order to make a hydraulic calculation of a warm floor, it is necessary determine the amount of heat lossarising during its operation. They are equal:
Q = (V * Pt * k) / 860
V — the volume of the room (it is found by multiplying the area by the height of the ceilings);
Pt — the temperature difference between inside and outside the premises (to determine it, +20 C⁰ is taken as a basis — the temperature comfortable for a person in the room and the smallest negative value characteristic of this climatic zone in winter, for example ‑30 C⁰, etc.).
K — coefficient of heat resistance of the house (from 1.5 to 2).
Here it is necessary to remember that if the amount of heat loss per 1 sq.m of area exceeds 100 W, the room needs additional insulation. This is due to the fact that poor thermal insulation can lead to heat losses of up to 80 watts per square meter. m.
For those who find these calculations too complicated, a special program for calculating a warm water floor, which can be found on the Internet, can help. Example: http://teplo-info.com/otoplenie/raschet_teplogo_pola_online etc.
It is better to entrust the performance of basic design calculations and the selection of material when laying the floor to qualified specialists in this field. The same applies to the calculation of the electric floor heating.
In addition to the power of the heating system and the quality of the thermal insulation of the house, the heat in it will depend on other factors.for example:
- Thickness and type of insulation gender.
- Varieties of flooring.
- Number of windows indoors and the method of their glazing.
- Room location relative to other rooms in the house, etc.
The next step in the design of this heating system is the calculation of the pipe pitch for underfloor heating. The uniformity of space heating and the required length of the pipeline depend on this.
Calculation of the length of the warm floor can be done independently, taking as a basis the data on the required power of the heating system, comparing the area of u200bu200bthe pipeline with the temperature of the coolant running in the system, according to the formula:
L — pipe length;
S — the area of the heated room;
N — laying step;
1.1 — pipeline margin of 10% (for bends).
When calculating a pipe for a warm floor, in this way, the length of the pipe to the collector, including distribution and return, must also be added to the value obtained.
In addition, the calculation of the warm floor by area is carried out by a graphical method.
To do this, on a sheet of graph paper placed over the sketch-project of the house, the location of the heating circuit is marked in accordance with the following rules and regulations:
- The length of the pipe in the heating circuit must not exceed 120 m. At the same time, there should be no joints and breaks at its outlet from the pressure manifold and the inlet to the return line.
- Pipes in the contour spiral should be located in increments of 10–15 cm.
- The thickness of the screed must match the diameter of the pipe. That is, for a pipeline of 16 mm, the fill layer should be 6 cm.
On average, pipe consumption per 1 sq. m of area is about 5 linear meters with a distance between the turns of 20–30 cm. That is, for a room of 20 square meters. m will need about 100 m of pipes. To facilitate the calculations, you can use a special calculator for calculating the underfloor heating on the Internet.
The temperature of the coolant in the system and the speed of its movement are determined by the averaged values:
- To warm up the surface to the optimum 25 — 37 ⁰С, its temperature should be 40–55 ⁰С.
- In this case, the coolant must move at a speed of 27–30 l / h (for a circuit with a diameter of 16 mm).
The pipe laying step is determined in accordance with the draft. For edge sections, it should be 10 cm, for the rest of the floor surface — 15, 20, 25 cm, but not more than 30 cm. For accurate calculations, there is also a program for calculating a warm floor, which can be found on specialized sites on the Internet.
Pipe laying methods
Having decided on the number of pipes and their diameter, you can proceed to the next important point: choosing the method of laying them.
It is used in rooms with internal walls, with an insulated outer wall. From a hydraulic point of view, this method is the most economical. The main disadvantage of this layout is the large temperature difference at the start and end points of the pipeline. This is due to the fact that hot water is supplied from one side, that is, at the end of the room, the cooled coolant will move to the return line, and the temperature there will be lower.
In addition, this option for laying pipes is quite laborious. Quite often it is made with a pipe pitch of 20 cm or more due to the fact that it is very difficult to bend them for a smaller pitch, especially when it comes to a pipe with a diameter of 18–20 mm. It is most rational to use such an arrangement of pipes in sanitary areas where it is necessary to bypass plumbing fixtures and devices, as well as to align adjacent areas of heating circuits.
This method has the same drawback as the previous one: uneven heating at different points in the room. Therefore, when using it, pumping units of increased power are needed, pumping water in the system at high speed.
Spiral or snail
With this method, the layout of pipes is made from the perimeter of the room to the center. Thus, uniform heating of the entire surface is achieved, which makes the operation of the warm floor as convenient and comfortable as possible. When laying in a spiral, pipes can be laid out on surfaces with any step, starting from 10 cm. This method is suitable for premises of any purpose and area.
For your floor to perform at its best, it is necessary to ensure its thorough thermal insulation, since, in its absence, heat loss can be 15–20% . To create a heat-insulating layer, the following materials are used:
- Mineral wool.
- Foam concrete.
- Glass wool.
- Technical traffic jam.
If there is an unheated room under the base of the floor, the thickness of the thermal insulation layer should be 20–25 cm.
Recently, special mats for thermal insulation have become widespread, which are plates with a minimum density of at least 25 kg / m3. Thanks to their use, heat during heating spreads in the “right” direction: from bottom to top. The most popular type of products of this type are polystyrene foam mats made by hydropellent stamping.
- high density (40 kg/m3).
- The presence of an upper relief structurein which it is convenient to mount pipes with a diameter of 18 mm.
- Ease of installation due to the presence of a lock connection, as in a laminate.
- Excellent thermal and sound insulation qualities.
Prior to installation, the cost of a warm floor is also calculated, which makes it possible to estimate the amount of financial costs for the entire range of works on the installation of a water or electric heating system.
Thus, in order for underfloor heating to perform its functions to the fullest and work efficiently and economically, it is necessary to draw up appropriate projects and make the necessary calculations.
This work can be entrusted to qualified specialists who will be engaged in the further installation of the heating system or perform it on their own by calculating the warm water floor using an online calculator.
In any case, well-made calculations will save a lot of money that will have to be spent on the future operation of underfloor heating, and will significantly increase their energy efficiency.