Selecting the type and installation of heated floors

Full heating of the room gives a much greater effect than local heating using a heater or battery. Full heating means heated floors. This method of heating a room was used in Ancient Rome. Back then, the prototype of a modern heated floor looked like a furnace with a pipe running under the floor and releasing gas. Today, heated floors operate much safer, as water or electricity is used for heating.

There are three types of heated floors:

• electrical,
• water,
• infrared.

Electric heated floors

Since electricity is an environmentally friendly energy carrier, this method is used in various buildings and premises. Floor heating is carried out using a one- or two-wire resistive cable. In the case of a single-wire resistive cable, a single conductor with high resistance is used. In a two-level cable, a copper conductor is laid together with a resistive one.

Also read materials:

On the outside, an insulating and heat-resistant shell, as well as a grounded shell, is used.

Heated water floors

Heated water floors are a structure made of pipes with hot water supplied from a gas or electric boiler. This is the most economical type of heated floors. The downside is that heated water floors are not allowed to be installed in apartments of multi-storey buildings, with the exception of the first floors.

Heated water floors are optimal for cottages and private houses.

Infrared heated floors

This type of flooring has appeared on the construction market relatively recently. For the operation of such floors, a film with infrared radiation is used. Anatomically, it looks like strips made of carbon conductors embedded in a polymer film. The thickness of this film is only 0.4 mm. Its main advantages include ease of installation and operation without screeds. Infrared floors do not emit harmful radiation. They are more economical in comparison with the two previous types of floors. When choosing a flooring covering over film, you need to consider that some of them may not withstand heat. These types of coverings include parquet floors and varnished flooring.

How to install electrically heated floors?

Electrical floor coverings can be used:

• as the main heating method;
• as an additional one.

So, if electric floors will be used as the main source of heating, then it should be no less than 5 cm. In this case, the area of ​​​​the installed floors should be about 70% of the total area of ​​​​the room. As an additional source of heating, electric floors are used to maintain a general microclimate together with other heating devices. For this purpose, they are used for bathrooms and swimming pools, as well as for apartments on the first floors.

Before you begin installing heated floors, you need to make sure that the electrical wiring is ready to connect additional power. You should also know what allowable current can pass through the fuses.

Installation of concrete water floors takes place in several stages:

1. The entire room must be divided into equal sections, their area should not exceed 40 square meters.
2. The rough surface of the floor must be covered with insulation materials.
3. Next, you should lay the reinforcing mesh and install the pipe contours.
4. The heating system needs to be tested.
5. made of concrete.
6. After all the above steps, you can proceed to finishing work.

Marking the room is necessary in order to avoid cracks in the concrete screed due to temperature changes. The ratio of plots should be 1:2.

There are many ways to lay pipes, for example:

• spiral,
• double snake,
• snake

However, it is worth considering that when installing pipes in internal walls, you need to take as small a step as possible. At one end the pipe must always be attached to the supply manifold, and at the other - according to the design diagram.

Even in ancient Rome, a floor heated by stove gases was known, but over time the principle was lost. In Korea, this method has existed for thousands of years, and currently the country is one of the leaders in the production of heated floors.

Modern technologies for heating a house through the floor implement two methods: electric and water. It is more convenient to use electric heating elements. Heating with hot water through the floor in multi-storey buildings is prohibited. In a private home, its use is beneficial if a heat source other than expensive electricity is used.

Compared to radiators, heated floors are 10-15% more economical, since the comfort zone moves down and less energy is required to heat the room.

Calculation of underfloor heating power

If electric floor heating is the main one, its power should be 180-200 W/m2, if additional - 120-140 W/m2. It is selected by the strength of the current passing through the heating cable, or the distance between the laid turns.

It is advisable to make the power a little more than the calculated one, since the thermostat turns off the heating when the required temperature is reached. About 80% of the room area is heated. The distance from the walls is 5-7 cm. The cable should not be laid under household appliances and bulky furniture without legs.

The advantage over radiators is the uniform heating of the room. Due to this, it is possible to reduce the average temperature by 2-3 o C, which will reduce energy consumption. The most effective underfloor heating will be under ceramic tiles. It should be remembered that it can be not only cold, but also hot for the feet. Here it is advisable to use a separate thermostat that maintains a comfortable temperature.

Heating elements

The following floor heaters can be found on the modern market:

• cable;
• film infrared;

Before you make a heated floor, you should choose the right one from all the variety.

The principle of operation of all types of elements is the release of heat or radiation when an electric current passes.

1. Cables are divided into resistive and self-regulating. The first has constant power and can be single- or double-core. Self-regulating consists of two parallel conductors with a conductive polymer located between them. When the temperature changes in individual sections, the current in them changes, and the cable is not in danger of local overheating. It is mounted in a cement screed 3-5 cm thick.
2. The film infrared heater consists of a conductor in the form of strips of laminated carbon foil. Electrical current is supplied through conductors to graphite strips, which generate infrared radiation, heating the flooring located above. Unlike cable, heat is evenly distributed over the entire surface, like the sun's rays. The heater is designed for installation under floor coverings without glue or screed. It does not tolerate alkaline environments well, but with waterproofing it can be laid under tile adhesive.
3. A heating mat is a thin cable with one or two cores glued to a fiberglass mesh. The elements are connected to each other and to the power source using special terminals. Their width is 0.5 m, and their length can vary. Even for complex layouts, they are easy to assemble by connecting to each other with terminals. The joints are additionally secured with sealant or tape. The mats can be placed in the adhesive layer when laying tiles. This does not require waterproofing.

How to install a heated floor

There are different ways to create a warm floor. Heating in each of them is carried out by a certain type of heaters.

Preparatory work

In most cases, thermal insulation is used, especially if underfloor heating serves as the main means of heating. The material used is polystyrene foam with a density of 35. Depending on what is located below, its thickness is chosen as follows:

• concrete slab on the ground - 100 mm;
• balcony or 1st floor with a cold basement - 50 mm;
• first floor with heated basement - 30 mm;
• room above the first floor - 20 mm.

Thermal insulation is glued or fastened with dowels (at the same time as the mesh). Floors are leveled if necessary. If the distortions are large, a rough screed is laid. The floor is treated with a primer that improves glue adhesion and protects against mold. A waterproofing film is laid on the insulation. A flexible tape insulator is laid along the walls. You can use foam strips.

A recess is made in the wall under the thermostat and a groove is made to the floor.

Cabling

You can lay out a heated floor yourself if you follow all the instructions correctly. The heating cable is laid with a given pitch in the shape of a snake. It is fixed to the metal mesh with mounting tape.

A thermostat is installed in the wall. It is placed in a mounting box, fixed with alabaster in a recess in the wall. A corrugated tube with wires comes out of it through a groove, which goes into the heating zone. The temperature sensor is located between the turns of the wire. You should immediately consider the option of replacing it without destroying the screed. Places where heating is not required should be avoided.

After installation, the cable resistance is measured, and the electric floor heating is checked for functionality, after which it is de-energized until the end of operation.

Screed

The screed is prepared from a solution of cement and sand in a ratio of 1:3 with the addition of a plasticizer. The floor will be durable if its thickness is made at least 3 cm. Fiber fiber can be added to the mixture for reinforcement. Laying is carried out according to the beacons, with the mortar leveled according to the rule. As soon as the screed has dried, lay the ceramic tiles on a special adhesive designed for heated floors. Final hardening occurs within a month. Before this time, the floor cannot be turned on.

Laminate can also be used as a covering for underfloor heating, but it must be made specifically for this purpose. Ordinary material is afraid of low humidity, and also releases harmful substances when heated.

How to use a heated floor

Warm floors are convenient because there is no direct access to the heaters. In addition, when using it, the heating temperature is low. Typically the floor is turned on at 70% of maximum power. In our climate, it is better to use it as a means of additional heating. Using underfloor heating as the main source of heating is not the most economical way due to the high cost of electricity.

It is especially convenient to use electric flooring where ceramic tiles are used. Its high thermal conductivity requires additional heating so as not to create discomfort for the feet. This heats the entire room.

Conclusion

Electric underfloor heating creates comfort when used as an additional source. It can be laid in a cement screed, in a layer of tile adhesive or directly under the laminate. The uniqueness of the elements lies in the fact that any of them provides the necessary heating of the floor surface and the room.

The floor is heated with electricity or water. Both methods are imperfect and have pros and cons. About, and in this article we will talk about how to make a warm floor using water and pipes, or rather, about how to make a water heated floor with your own hands and what is needed for this.

Operating principle of water heated floor

The coolant is heated in two ways:

In both cases, a reduction in coolant temperature is required: the operating parameters of the radiator system for which these sources are created are in the range of 65-95°C, while underfloor heating requires only 35-55°C. This range is explained by the fact that the temperature of a water heated floor, according to SNiP, cannot be higher than 30°C. Agree that it will hardly be pleasant to walk on a hotter floor.

To achieve the desired temperature, the hot coolant is mixed with cooled water from the “return” before entering the pipes. This way the required temperature is obtained, and then, through the underfloor heating manifold, it enters the pipes.

This is all the mechanics of how a water heated floor works, but there are some technological nuances that increase its comfort and simplify adjustment.

Temperature adjustment

In order to be able to maintain a comfortable temperature for the heated floor, there is a special device - a thermostat, or as it is also called a thermostat. This device works in conjunction with sensors that measure the temperature of the floor and coolant.

Water heated floor pie

Now let's talk about the structure of a heated floor: so that you know what and in what order to do when filling it with your own hands. A water heated floor is a multi-layer structure. An approximate diagram is shown in the figure.

Thermal insulation is first laid on a flat base (height difference no more than 1 cm per 1 m2). The choice of material and its thickness depend on the initial insulation of the floor and which room is located below (if there is one). The goal is to achieve minimal heat leaks. Then heating will be economical (you will pay little for it, and the house/apartment will be warm). Therefore, when choosing a material and its thickness, it is better to take the characteristics with a reserve: in this case it will definitely not be worse. If there is a heated room below, thermal insulation of 20-30 mm is sufficient; if there is an unheated basement or soil below, a solid thickness of 50 mm or more is required; in the northern regions, the thickness of the insulation can be from 100 to 150 mm.

Installation of a “pie” of a water heated floor

A damper tape is rolled out around the perimeter of the room or thermal insulation tape is laid; you can use polystyrene foam, expanded polystyrene or other sheet insulation (about 10 mm thick) cut into strips 10 cm wide; you can also use mineral wool cardboard.

This measure is necessary, firstly, to ensure that cracks do not appear around the perimeter of the floor due to thermal expansion, and also to reduce heat loss through the walls and foundation.

After the pipes are laid, you can begin pouring. A special composition is used - with additives that increase thermal conductivity. In some cases, to increase the strength of the structure and additionally protect the pipes from mechanical loads, a reinforcing mesh is laid on them, and only then the solution is poured. The concrete layer should be such that there is at least 3 cm of solution above the pipe. Only with such a thickness will the floor not “walk” underfoot and its temperature will not have pronounced hot/cold bands.

And there is one more nuance: Pouring a warm water floor with a solution should take place when the pipes are filled, that is, under pressure. Then they take on “working” dimensions and no problems will arise during further operation.

The most unpleasant moment in all this is the long drying time of the screed. At least 28 days must pass after pouring for it to acquire its final strength. But further work can begin after 7-10 days, if the average daily temperature was higher than +17°C.

While the concrete is gaining strength, the heated floor cannot be turned on. An increase in temperature will cause cracks to appear, which will negatively affect the thermal conductivity of the floor and its durability. So wait patiently for it to dry naturally.

Beacons have been installed for pouring screed - for many floor coverings the floor must be perfectly flat. Please note: thermal insulation is installed around the perimeter. Its height is higher than the height of the finished floor; after the screed has dried, the excess is cut off with a knife. A model with markings, like the one produced by Valtec, was used as a substrate for thermal insulation.

These are only the main layers of the water heated floor cake. Often, at the very bottom under the thermal insulation, a hydrobarrier (thick polyethylene film) is laid. It will protect the lower premises in case of leakage. It is often recommended to lay a heat-reflecting coating on the heat insulator so that the heat does not go down, but is reflected upward. But here it is worth remembering that it is useless to place aluminum foil or foil-coated materials in the screed: after a month or two, the foil collapses and turns into dust. If you use a heat-reflecting coating, it should be metallized. It is very similar to foil, but is made of other metals that perform well in cement-sand mortar for many years. As you can see, installing a water heated floor is not an easy undertaking, with a large number of components and components.

System parameters

To make a warm water floor with your own hands, you need to know a few more features and rules that you cannot do without.

Which pipes to use

Pipes for warm water floors can be used as follows:

All these types of pipes can be used in both screed and deck systems. Moreover, it is necessary to lay coils of pipes without connections inside the floor. If the length of one bay is not enough, you can make several contours, each of which is displayed on.

Pipe parameters: diameter and length

The length of the pipe in one circuit depends on the diameter: the smaller the diameter, the shorter the length can be used, but circuits that are too long are unprofitable. And not only because a meter of such a pipe costs more, but also because there is too much water in the system, and it becomes too sluggish and ineffective. For any pipe material, it is recommended to use diameters from 16 mm to 20 mm. This cross-section is sufficient to heat any domestic space.

• When using metal-plastic pipes with a 16 mm cross-section, the maximum length of the circuit is 100 m, but in reality it is better not to exceed 60-80 m.
• When using pipes of the same material, but with a cross-section of 20 mm, a maximum of 140 m can be laid, but in reality - 100-120 m.

Approximately the same loop sizes can be used for other materials. If the declared quantity is not enough for the premises, several circuits are made, each of which is connected to the corresponding input/output of the collector.

If there are several circuits, the damper tape is rolled out not only around the perimeter of the room, but also separates the circuits. And one more nuance: in order to make it easier to maintain the same temperature with several circuits, it is advisable to make the circuits the same length.

Pipe laying diagrams and steps

Water heated floor without screed

Warm floors with screed have several significant disadvantages:

• it has a large height - the thickness of the water heated floor is 8-10 cm depending on the thermal insulation layer,
• weighs a lot (a cement-sand mortar with a layer thickness of at least 4-5 cm over the entire area has a solid mass);
• the screed takes a long time to dry;
• has low maintainability.

All these disadvantages lead to the fact that many people are looking for options for installing heated floors without screed. There is such an opportunity and this is it. They do not require “wet” work, are light in weight and height, and are quickly installed. Therefore, they are often used in houses with wooden floors (they cannot be screeded because of their heavy weight) or in rooms with low ceiling heights, where losing 10 cm to install a heated floor is unacceptable.

There are two types of floor heating systems: polystyrene and wood. In both cases, these are slabs in which there are special grooves for laying pipes. Polystyrene boards are a well-known high-density foam plastic in which grooves for pipes are molded. Wooden systems are made of chipboard or OSB. Since these materials have low thermal conductivity, to increase heat transfer, metal plates with similar grooves are placed in the grooves and on the plates, and pipes are already fixed in them.

After installing the pipes, you can immediately begin laying hard surfaces - laminate, parquet or boards. When using a soft coating, a rigid base is required - sheets of plywood, chipboard, etc. They are laid directly on top of metal pipes, secured, and carpet is rolled out on top or placed. When installing a heated floor without a screed under the tiles, the adhesive can be placed directly on the metal plates, but a special composition for heated floors must be used.

As you can see, it’s even easier to do it with your own hands than for a screed - the principle is clear, the work is not the most difficult, and not a lot of materials will be used. Moreover, you can not only mount ready-made polystyrene or fiberboard boards, but do everything yourself. It will take more time, but it will require less money.

Results

Do-it-yourself warm water floor is a difficult undertaking to implement, but realistic. Of course, you will spend more time - you need to figure everything out, digest a lot of information. But you will do everything yourself, and according to your mind, and not in the way that is faster or more convenient, and as hired workers often do. You will also save quite a decent amount - the services of builders are not cheap at all.

Ceramic tiles are an excellent material for flooring, and in some of their characteristics they leave far behind all “competitors”. So, in matters of hygiene, strength when installed correctly, durability, resistance to biological processes, humidity, thermal changes, it probably has no equal. If we add to this the high decorative properties and the possibility of implementing interesting design compositions, then the popularity of tiles among homeowners is quite understandable.

However, the main negative quality of tiles is the coldness of the material, which significantly limits the scope of its application. Even in those rooms where it is the best option - bathroom, kitchen, toilet, etc., it is not entirely pleasant to put your bare foot on the floor in the cold season. There is only one way out - to organize heated floors under the tiles.

There are basically two options - a warm water floor or heating using electrical energy. This publication is devoted to how to organize an electric heated floor for further tiling with ceramic tiles.

So, you can lay both water and electric heated floors under the tiles. Water circuits are discussed in separate articles, but for now - about some of the advantages of electric heating:

• The temperature level in electric heated floors can be quickly and quite accurate regulation - water floors are much more inert in this regard, and some simply directly depend on the temperature of the coolant from the centralized heating system.
• Installation of an electric heated floor is simpler, often not requiring pouring a new screed - in water floors it is required. In addition, in order for the water circuit to justify its purpose, the screed must be thick enough - and this is a significant expense, labor intensive, and, most importantly, large additional loads on the floors, which is not always acceptable. And the height of the ceilings in standard high-rise buildings does not always allow the level of coverage to be raised high. With electric heating, such massive screeds are not required.
• For the reasons stated above, it is simply impossible to organize a heated water floor in a multi-storey building. By the way, the heat supply organization may not give permission for this due to too significant heat losses.
• Another plus of electric floors: there is no risk of a major accident with the risk of flooding your or even your neighbor’s apartment.

The disadvantages of such floor heating systems include only the relatively high cost of electricity. However, if the system is installed and adjusted correctly, and the heated floor acts only as an addition to the overall heating system, then the operating costs will not be particularly noticeable.

But the comfort in the room will clearly increase - a layer of ceramic tiles, being a good “heat accumulator”, is not only pleasant in itself, but also creates rising currents of warm air, evenly distributing heat throughout the volume of the room.

Which electric floor heating system is preferable?

First of all, if you decide to install electric floor heating under the tiles, you need to decide on its circuit diagram. There are four main options.

Warm floor with heating cable

Such a system has two extremes: it is the most inexpensive in terms of the cost of the necessary elements and accessories, but at the same time, it is the most labor-intensive method of all other electric heating options.

The main “tool” is the heating cable itself, which can also vary significantly:

• The simplest is single-core, with the usual resistive principle of operation - heating the conductor when an electric current passes, like a regular spiral, for example, in an iron.

The big drawback is the need to “loop” the cable to complete the circuit, which will require a special installation scheme. Heating is carried out simultaneously and evenly along the entire length - this is also not always good from an economical point of view.

• A two-core resistive cable has two conductors, one of which is a “spiral”, and the second only completes the circuit through a special termination. Installation, of course, is much more convenient, but the rest shortcomings remain same.

• Self-regulating two-core heating cables are the most modern and successful option. The two conductors here are separated by a semiconductor matrix that heats up when current passes. What is the characteristic feature: the conductivity of the matrix directly depends on its temperature - the higher it is, the less current passes. Moreover, this is typical for any, even the smallest section of cable. A unique self-regulation effect appears - maximum heating occurs only in cold places, and when a certain temperature is reached, the matrix simply “locks.”

The economic effect of such a floor is obvious. AND more one important advantage is that such a cable is easily cut to the required length - there are special sections for cutting with certain steps away from each other.

Mesh heating mats

A very convenient and extremely popular type of electric heated floor. By and large - the same two-core heating cable, but only fixed in a loop on a fiberglass mesh.

Such a system cannot be called cheap when purchased, but its installation is simple and straightforward. In this case with ceramic tiles, there is simply no need for any screed on top of the mats - the tiles can be laid directly on them.

Infrared rod heaters «Unimat"

The installation of such heaters also does not require any pouring on top - very convenient for installing ceramic tiles. In this system, two conductors are connected along their entire length by parallel rod heating elements that emit infrared radiation.

Rod infrared heaters "Unimat"

All rods are independent of each other and work with self-regulation, reducing energy consumption. The system is convenient, but its cost is even higher than that of mesh mats.

Infrared film heaters

One of the most economical modern floor heating systems, but not quite suitable for ceramic tiles. The reason is simple - the film will simply block the possibility of normal adhesion of the tile adhesive to the concrete base. Making the screed too thick on top pl elements - it is simply meaningless from the point of view of the principle of their operation. So such a heating system is more likely for “floating” floors - laminate, linoleum parquet, etc.

The film has perforations for supposedly good adhesion to the concrete base. However, according to experts, practice shows that the tiles on such a floor will very soon begin to “play.” There is, however, a way to lay such a floor using “liquid nails,” but this is very expensive and also raises concerns about the overall strength of the tiled covering.

Is everything ready to go?

• A warm electric floor system should release heat into the room, and not waste it in vain on heating the concrete floor. Therefore, you will need high-quality thermal insulation, under the rough screed, or roll flooring thermal reflective material (for example, foil foam) before laying the cable and pouring the closing screed.
• You should definitely check the completeness of the system - the presence of a temperature sensor and a control panel - a thermostat with the functions of turning on the system and setting the required temperature. This automatic device monitors readings from a built-in temperature sensor floor and automatically stops supplying electricity when it heats up to a user-set level.

• If you choose a system with a cable, you will need to purchase either mounting metal tapes or reinforcing mesh. The cable loops, after they are laid, will be attached to it.
• To compensate for temperature expansion, the perimeter of the room will need to be taped with a special damper tape.
• To lay the cable to the thermostat, you will have to punch a groove, and for the device itself, you will have to drill a socket in the wall. This will require a hammer drill.
• To check the safety of the assembled system, you need a special measuring device - a megger.
• And, of course, you need the required quantity of building materials and a set of tools for pouring screed or for installing the inlet directly onto the heaters - depending on the chosen system.

How to properly place heating elements

In order for the floor to fully meet expectations, it must be carefully constructed, and based on this data, a laying scheme must be drawn up, taking into account certain features.

1. First of all, you need to decide on the number of underfloor heating elements. In this case, they proceed from the intended purpose of the system being created, the area and specific features of the room:

• In the case where the “warm floor” is planned only as an addition to the overall heating system, about 100 - 130 W/m² will be required. If it becomes the main source of heat, the figure rises to 150 W/m², and for the first floors or for private houses with floors on the ground – even up to 180 W/m².
• Heating elements must cover at least 70 ÷ 75% of the room area. Cables should not be laid in places where stationary furniture will be placed - no closer than 50 mm from it. The same condition applies to stationary heating devices, only here the minimum distance increases to 100 mm. Ignoring these rules leads to overheating of cable turns in closed areas and to rapid failure.
• The required cable length is calculated as follows:

The heating area is calculated ( S)– according to recommendations given higher;

The required specific power is determined - ( PS) per unit area.

The specific power is taken into account ( Pp) the cable itself per 1 meter in length (its passport characteristics);

The required cable length will be: L = S × Ps : Pp

2. Now you can proceed to drawing up a laying diagram. What is taken into account:

The installation location of the thermostat is immediately outlined - this is where the “cold” ends of the cable should fit. This is where the temperature sensor wire will come from;

The temperature sensor itself should be located in the center of the cable loop, at a distance of about 500 mm from its beginning.

The distance between adjacent cables in the loop is determined ( H), based on existing, previously obtained data: H = S × 100: L.

The installation diagram should first be worked out on paper, and only then, after careful checking, transferred to the floor surface for installation in place.

How to install a heated floor with cable

• First of all, carefully prepare the floor surface - carry out minor repairs if necessary, clean it of debris and dust.
• A socket is made on the wall for installing a thermostat (its distance from the floor can, in principle, be any, but not less than 300 mm). A groove with dimensions of at least 20 × 20 mm is made to it. It is necessary to connect the power supply cable to the installation site of the regulator - this issue should be discussed with a specialist electrician.
• Spread over the entire surface of the floor thermo-reflective substrate. The sheets are laid end-to-end with the obligatory gluing of the seams with special tape.

• The next step is to install a reinforcing fiberglass mesh or attach mounting tapes to the floor to secure the cable.
• In accordance with a pre-drawn diagram, the cable layout is carried out.

If the cable is single-core , then the “cold” ends are connected through the couplings, which will go to the thermostat.

If the cable is single-core, both ends are connected to the thermostat

Using two-core The far end of the cable must be closed with a special plug coupling.

• The temperature sensor and its wire are inserted into a corrugated tube Ø 16 mm, with a length that allows it to be installed in the desired location and routed to the location of the thermostat. Such a tube should ensure free movement of the temperature sensor inside - so that it can be easily replaced in case of failure. The tube section is closed with a plastic plug.

• After installation is completed, it is necessary to check the electrical circuit of the cable - its conductivity and total resistance (must correspond to the passport data, with a deviation within ± 10%), and insulation resistance - measured using a megger. Safety will be maintained if this indicator is at least 20 MΩ.
• All wires are connected to the corresponding terminals of the thermostat. Only after this will it be possible to supply power and check the functionality of the system by briefly starting it. If everything works fine, the power is completely turned off to proceed to pouring the face screed. The groove on the wall is sealed with mortar, the regulator is finally fixed in its normal place.
• A prerequisite before starting pouring is gluing the damper tape around the entire perimeter of the room.
• The thickness of the screed cannot be less than 30 mm. Its filling can be carried out in the usual manner, with concrete mortar with the installation of beacons, or using self-leveling compositions. There are also special building mixtures directly intended for these purposes - they are enriched with plasticizers that eliminate the formation of voids and ensure the integrity of the coating.

After pouring the screed and gaining the necessary strength, you can proceed to laying ceramic tiles - this process in this case will not differ in any way from conventional cladding methods.

It is possible to operate a heated floor system with laid tiles in the design mode only after 3 ÷ 4 weeks from the date of pouring the screed.

Video: installation of a heated floor with a heating cable

Some features of installing floors with insulating mats

What are the characteristic features of using an electric floor heating scheme for tiles using ready-made mats:

• The base surface must already have internal thermal insulation, and thermo-reflective the substrate is not spread before laying the mats. produced with silicone heat gun or simply using strong tape.

• After laying all the mats, switching and checking electrical parameters, they proceed to installing ceramic tiles directly on the heaters themselves. The layer of tile adhesive should be 8 ÷ 10 mm. It is recommended to use a special adhesive for underfloor heating that is resistant to heat and frequent thermal changes.

• You can use the heated floor after laying the tiles within 15–20 days (this period should be specified in the instructions for use of the specific tile adhesive).

Video: installation of heating mats under ceramic tiles

There are small nuances when laying rod mats. For the automation to work correctly, they will definitely need thermo-reflective substrate, but the thickness of the tile adhesive when laying the coating must be at least 20 mm. Sometimes in this case it is more profitable to use a self-leveling coating, and only then lay the tiles.

Approximate diagram of installation of a heated floor under tiles with UNIMAT heaters

So, organizing electric floor heating under the tiles is a completely doable task, although quite labor-intensive. It will require special care and precision, especially when switching electrical connections. However, if you follow all the technological steps exactly, everything should work out.

Building your own home always involves solving a huge range of problems, and one of the most important is always ensuring a comfortable microclimate in all residential areas. In the harsh winter conditions that characterize most of Russia, organizing an effective heating system becomes a major task.

Most owners of private housing prefer the usual water heating schemes, open or closed, with the installation of radiators in the premises in the required calculated quantity. This scheme is time-tested and has long proven its effectiveness. However, it also has serious disadvantages - uneven heating of rooms and the creation of horizontal convection flows that are not always pleasant. It doesn’t matter, in a private house it is much easier to eliminate such disadvantages than in a city apartment - nothing prevents the owner from making water floor heating with his own hands.

If in a multi-storey building such a modernization of the heating system is not always possible for a number of administrative or purely technological reasons, then in the conditions of individual housing, when you have your own and there are no significant restrictions on the height of the premises, this seems to be a completely feasible task. Of course, it cannot be called completely simple - you will have to carry out a lot of calculations, purchase high-quality materials and equipment, and perform a significant amount of construction and installation work.

Basic design of a water floor heating system

At its core, a water “warm floor” is a system of pipes located under the surface of the floor covering, through which coolant circulates from a common heating circuit.

Schematically, the general “pie” of water floor heating looks like this:

The usual structure of the heated floor “pie”

• The basis for installing a warm water floor is usually a leveling concrete screed (item 1). It may already have its own insulation (for example, expanded clay) or be without it.
• To prevent absolutely unnecessary spending thermal energy to warm up the base of the floor or interfloor ceiling, a layer of effective thermal insulation will be required (item 2). This level is not laid only if thermal insulation is provided by the design of the leveling screed itself.
• Another layer of thermal insulator - foil backing (item 3) will increase the heating efficiency by reflecting the heat flow from the pipes, directing it to warm the upper layers of the floor. In some cases, when using special insulating mats for heated floors, they do without it.
• Heating of a heated floor array is necessarily accompanied by its rather significant temperature expansion. To prevent deformation around the perimeter of the premises, use a special damper tape (item 4), which will serve as a compensator.
• Main element T heated floor - a system of pipes through which the coolant circulates (item 5). In the process of laying out the pipes, they are attached to the thermal insulating substrate with special brackets (item 6) or are fixed by other methods, which will be discussed below.
• Most often, a concrete screed is poured over installed pipelines (item 7). It not only becomes a reliable basis for laying the finishing coating (item 8). The screed will act as a powerful heat accumulator and promote uniform heating of the entire floor surface, so there are certain requirements for its thickness.

Certain changes may be made to the presented diagram. For example, in some cases, when using special components, you can do without pouring the top screed by using the so-called modular design of a heated floor with profile thermo-reflective metal plates.

However, it is not enough to simply lay the pipes - it is necessary to ensure stable circulation of the coolant through them for uniform heat transfer. Therefore, the most important component of a heated floor is the manifold system, thanks to which the required liquid pressure is created and the required temperature is maintained. Usually, special manifold cabinets of one or another level of complexity and saturation with automation are installed for these purposes.

Now, after a brief acquaintance with the general structure of the underfloor heating system, it makes sense to consider all its elements in more detail.

What materials are required for a water heated floor?

Let's leave out the device of the lower leveling screed - this rather relates to general construction work. The main condition is that it ensures a flat and horizontal surface and has appropriate waterproofing. The concrete surface should not have significant flaws (cracks, crevices, potholes, areas of instability, etc.)

In addition, we proceed from the assumption that the starting screed does not have significant insulation. Means, Firstly we have to deal with its thermal insulation. For these purposes, special mats for heated floors are usually used.

Thermal insulation mats for heated floors

Mats for heated floors can be made in several versions.

• In some cases, for example, when installing water heating on the second floor of a house, provided that the rooms on the first floor are heated and the general thermal insulation requirements of the building are met, rolled mats made of foamed polyethylene with a foil coating may be sufficient.

Their thickness is insignificant - about 3 - 5 mm, however, they can effectively insulate the ceiling and redirect the heat flow upward. They are laid end-to-end in strips, with the metallized surface facing up, with obligatory gluing along the seams, preferably with foil tape.

• More reliable in terms of protection against heat loss are slabs made of extruded polystyrene foam. This material has a high density (about 40 kg/m³) and can easily cope with the load placed on it - the weight of pipes with coolant, screed, finishing coating, pieces of furniture and dynamic influences during operation.

As a rule, such slabs have a system of tongue-and-groove locks, which greatly simplifies their installation. The thickness can be different, from 20 to 100 mm - it is always possible to choose the right one, depending on the degree of insulation of the floor base. Typically, for floors on the ground or above unheated basements (basement rooms), a material with a thickness of 50 to 100 mm is used. If there is a heated room below, you can limit the thickness to 30 mm.

• More convenient to use are ready-made mats made from the same extruded (EPS), designed specifically for heated floors. They can be made in the form of rolls like a “tractor caterpillar” or like an “accordion”.

Very often they are immediately coated with foil thermo-reflective layer. Another significant convenience is that many of these mats have marking lines - this will significantly simplify the process of laying out the water circuit.

• The most modern and convenient approach would be the use of profile mats, which are designed taking into account the need to fix the water circuit pipes. They are provided with relief protrusions ( so-called "bobs"), arranged in a specific order. The shape of these bosses can be different, but they are always located in such a way that pipes of the required diameter are securely fixed between them.

The most comfortable are profile mats with polymer coating

The material for the manufacture of such mats is the same EPS, but usually they have a protective polymer coating, which also becomes an additional waterproofing barrier. Such mats have a system of locks for mutual interfacing, which ensures the solidity of the laid layer. Another advantage is that when pouring the finishing screed on top of them, no additional reinforcement will be required - this role will be taken over by the relief of the surface of the mats.

Prices for different types of heating mats

Heating mat

Which pipes will be optimal for heated floors?

Selecting high-quality pipes is the key to efficient and safe operation of a water floor heating system. Taking into account that the contours in most cases are embedded in the screed and access to them makes it impossible to repair or replace the damaged area, the material must be fully suitable for this function and be of exceptionally high quality.

Pipes for underfloor heating circuits must meet a number of mandatory requirements:

• They must have a reliable margin of safety, both to baric internal load and to external applications of forces. The optimal choice is the choice of pipes designed for a pressure of at least 8 bar.
• The use of seam pipes is absolutely excluded. In addition, the circuit closed by the screed must be uniform - there should be no welding or threaded connections in it (with rare exceptions, which will be mentioned below) - this is always a “weak spot” in which leaks or blockages cannot be ruled out over time .
• High anti-corrosion properties are a mandatory requirement. The material must be chemically inert. The weak point is the oxygen diffusion of the material, that is, the penetration of this gas through the walls of the pipe, which leads to the activation of oxidative processes. The best choice is pipes with a well-designed oxygen barrier.
• The inner surface of the pipes should be as smooth as possible so that excessive hydraulic resistance is not created and noise does not arise from the liquid flowing through the circuit.

Which of the modern materials may be suitable for laying a heating circuit:

• First of all, it is immediately necessary to abandon conventional metal HCV pipes, even if they are made of stainless steel - the inadmissibility of joints has already been mentioned.
• Not suitable for heated floors and. This material, of course, is good and inexpensive, but does not have the required flexibility. It will not be possible to bend it in accordance with the intended installation pattern, which means you will have to resort to the use of additional elements. A these are welded joints, the inadmissibility of which has already been discussed. On the Internet you can find photographs of such circuits with assurances of their complete reliability, but there is no need to repeat such adventurism.

• Copper pipes are good for everyone for these purposes - they are flexible, have excellent heat dissipation, and provide reliable roller or soldered joints. However, for all these advantages you will have to pay a very high price, so this type of material is still not widely used.

• Metal-plastic pipes seem to have been specially created for the floor heating system - they are flexible and hold the given bend shape well, have high heat transfer, and are easy to install. However, do not rush to immediately rush to the store to purchase them. The fact is that not every metal plastic is suitable for these purposes. That inexpensive option, which is very popular for creating external plumbing or heating networks, can play a cruel joke in the thickness of the floor. If you wish, you can find photographs with a torn pipe body - and this is a disaster for a circuit walled up in a screed. The main problem is that the market is oversaturated with inexpensive and far from high-quality goods. The aluminum layer in such pipes does not have reliable protection from oxygen exposure, over time it becomes brittle due to corrosion processes, and may not be able to cope with the pressure of the coolant.

RE-Ha pipe made of cross-linked polyethylene

• Modern cross-linked polyethylene pipes are a good choice. Special chemical treatment of the polymer creates multiple additional intermolecular bonds, and the material acquires the highest resistance to baric loads without losing its elasticity.

The symbol “PE-X” indicates the “cross-linking” of polyethylene. From the point of view of quality, the best performance is achieved by the material “PE-Ha”, which is treated with peroxide – the maximum percentage of “cross-linking” is achieved - up to 85%.

The material is very flexible, which makes it possible to lay it with a loop of only 150 mm in diameter. It is produced in large coils, and this allows you to create a solid contour of any required length.

The best option that combines the advantages of metal plastic and cross-linked polyethylene

• Maybe, the most optimal The choice for a heated floor contour would be pipes that combine the advantages of metal-plastic and cross-linked polyethylene. They have a multilayer structure - the inner and outer layers are made of PE-X, and between them, on on reliable adhesive base, there is a layer of aluminum welded using TIG technology (in a protective gas environment). Moreover, many manufacturers additionally equip their products with an intermediate oxygen barrier (EVON technology). This prevents corrosion of the aluminum layer.

Such combined pipes are usually marked PEX-Al-PEX. You can always purchase all the necessary components for connection to the heating system manifold.

• Another option for t rub is corrugated stainless steel. This is a relative novelty, but has already earned good reviews from masters involved in heated floors. Such pipes have excellent flexibility, high heat transfer, reliability, and protection from external influences due to the polymer film internal and external coating. Moreover, they are equipped with a system of fitting connections of such a degree of reliability that such joints can be removed into the thickness of the screed without fear of leakage. The only negative is the still extremely high price for such material.

Preliminary calculation and drawing up a floor laying plan

All practical steps for installing a heated floor must be preceded by the mandatory drawing up of a laying diagram and the necessary calculations.

• Before drawing up the diagram, the location of the manifold cabinet must be determined - this is the point where both ends of all circuits should be brought out. The location of this unit should ensure ease of maintenance and ease of supply of pipes from the boiler or existing heating system. Most likely, you will need a power connection point to operate the circulation pump. Typically, cabinets are placed so that they do not spoil the interior of the room - in a hidden place or by putting them into the wall. The height above the floor level is usually 200 ÷ 300 mm.
• For floor heating circuits, pipes with a diameter of 16 or 20 mm (in rare cases - 25 mm) are usually used. As a rule, 16 mm pipes are used when underfloor heating is planned as an additional element of the home heating system, 20 mm - if such heating becomes the main source of heat in the room.
• As already noted, the contour must be solid, without joints, but its length has certain limitations. You should not make a circuit with a 16 mm pipe longer than 50 ÷ 70 m, and with a 20 mm pipe - the limit is 100 m. This is explained by the fact that the force of internal hydraulic resistance over a too long section may exceed the liquid pressure created by the pump, resulting in a “closed loop” effect through which coolant circulation will become impossible. If this length is not enough for the existing dimensions of the room, you will have to lay two or even more circuits connected to one collector.

There are two basic schemes for laying the contours of a heated floor - “snake” and “snail”.

Basic pipe layouts - “snail” and “snake”

From the point of view of ease of installation, “snake” is, of course, preferable. However, this scheme is characterized by pronounced uneven heating of the floor - with distance from the beginning of the supply, the temperature of the coolant decreases noticeably.

When laying “snake”, the supply and return pipes are located parallel to each other, and thereby the temperature difference in them is compensated. True, for this you will have to work a little more when preliminary drawing the diagram and directly when laying the pipes in order to avoid mistakes.

Based on these basic patterns, many other variations of the styling pattern have been developed.

• The next important point on which the number of required pipes depends is the step of their installation. Depending on the degree thermal insulation room, average winter temperatures in the region, tasks facing the underfloor heating system (main or additional heating), this value can vary from 100 to 500 mm. It is difficult to independently determine this value taking into account all the criteria - the system of thermal engineering calculations is quite cumbersome. However, on the Internet you can find special ones that allow you to carry out such calculations with the required level of accuracy. It should be noted that placing pipes too often is an unnecessary waste of material and energy resources. And if the loops of the circuit are too far from each other, a “zebra effect” occurs - alternating cold and heated areas of the floor.

If necessary, a differentiated approach can be applied. In places where it is necessary to create zones of increased comfort or maximum heating (in the coldest areas), you can use a minimum laying step, but increase it in other areas of the room.

• When drawing up a diagram, you should provide for indentations from the walls (so as not to waste energy on heating these very heat-intensive structures). Typically, the pipe closest to the wall is located at a distance of 300 mm. You should not plan to place the circuit under permanently installed pieces of furniture.
• If you intend to lay several circuits connected to a single collector, then ideally they should be the same length - this will ensure uniform circulation through them. In any case, the excess length should not be more than 10-15 meters. However, sometimes this can be solved by installing special balancing fittings.
• Be sure to immediately calculate to what height the floor level will rise, whether the doors will open normally, or whether certain adjustments will have to be made to their design. And the total rise in level can be quite significant:

— The thickness of the insulating layer used – mats and substrate – is taken into account. This can already give 30 ÷ 100 mm of height.

— Mandatory concrete screed on top of the pipes. In order for the underfloor heating system to be effective, it is recommended to provide a thickness of this layer from 30 mm (for 16 mm pipes) to 45 mm (for 20 mm). An important nuance is that we are talking about the height of the screed from the top edge of the pipes. Thus, taking into account their diameter, we obtain a screed with a thickness of approximately 50 and 70 mm, respectively.

- if you add the thickness of the selected finishing coating, you will get the total amount of rise in the level of the floor surface.

• When using several circuits in one room, it is advisable to provide a compensatory gap in the screed between them. A similar approach is also necessary if the total length of the room exceeds 6 meters - it will be necessary to divide it into two sections, separating them with a damping joint, which must be filled with an elastic sealing compound.

In these places, it will be necessary to install pipes in a sleeve, the length of which on each side must be at least 150 - 200 mm.

Typically, a polymer corrugated tube of the appropriate diameter is used for this. Similar sleeves (pedestals) must also be installed if it is necessary to pass a pipe through the walls of the room.

• It is necessary to immediately consider a system for fixing pipes to insulating mats. There are no problems with profile mats - everything is already provided there. On flat mats you can do this in several ways.

One way or another, the screed will require reinforcement. Therefore, you can first lay a reinforcing metal mesh, and tie the pipes to them with plastic flexible clamps.

Special fastening brackets with “harpoon” tips are sold, which are convenient for fastening pipes to the polystyrene foam insulating substrate.

Pipe fixed with a harpoon bracket

It is convenient to use special mounting rails, metal or plastic, on which grooves or clamps for pipes of clamp or petal type are located.

Based on the drawn up diagram, you can easily calculate the required amount of material - pipes, insulating mats, mounting rails, damper tape and other elements. The required margin for supplying circuits to the manifold cabinet and connecting them to it must be taken into account.

Video: typical mistakes when designing a heated water floor

What is a collector unit?

It would be a serious mistake to believe that it is enough to connect the laid heated floor circuits to the heating pipes or to the boiler, and the system will immediately work in optimal mode. Its correct functioning is possible only if the required pressure is created, the distribution of coolant flows is well-established and balanced, and the required temperature conditions are observed. These are the functions that the collector unit must perform. It includes many devices, instruments and devices.

• As a rule, it includes a circulation pump. The pump that stands next to the heating boiler is unlikely to be able to cope with the task of providing the required pressure in all circuits - both in radiators and in heated floors. It is more expedient to provide a separate device that will be responsible for a certain area of ​​the house, connected to one collector.
• There are completely different requirements for the water temperature in radiators and in underfloor heating circuits. So, in convection devices the coolant can reach 70 - 80 degrees, but for floor heating this is unacceptable. It is considered normal to heat the floor surface to 27 - 29 ºС in residential premises, and a little higher - up to 35 ºС, in service, special or passage areas, where tiles are laid. Exceeding these indicators leads to a violation of the integrity of the screed due to its overheating, deformation and drying out of the decorative floor covering.

To maintain the required temperature level in the manifold cabinets, a regulation system is implemented using thermostats based on mechanical or electromechanical two-, three-, or even four-way valves. In these devices, the coolant from the half-summer pipe is mixed with the already cooled coolant from the return.

The control can be carried out manually or in automatic mode, when such a faucet is equipped with a servo drive connected to an electronic temperature sensor.

• The circuit pipes are connected to the combs of the supply and return manifolds. For the necessary balancing of pressure in circuits of different lengths, as well as for turning off any circuits if necessary, valves are provided.
• The operation of the heating system may be accompanied by the release of dissolved gases of their coolant. To avoid the occurrence of traffic jams, an automatic air vent valve.
• Instruments for visual monitoring of the operation of the system - a pressure gauge and a thermometer - will never be superfluous.
• It is possible to provide for the independence of the heated floor circuits from the general heating system. This becomes possible when installing a heat exchanger.

In this case, the circuits have a limited volume of coolant that receives the required heating from the general system. Such a warm floor is easier to regulate, but, however, it will require the installation of an additional safety group - a pressure valve and a membrane tank.

Correctly assembling and adjusting the mixing-collector unit is a task of high complexity. However, there is a way out - you can purchase ready-made kits designed for a particular area of ​​the room, the number of connection circuits, with varying degrees of equipment with automatic or manual control and adjustment systems.

Video: operation of a heated floor mixing-collector unit

After the manifold cabinet has been selected, purchased and installed in the place specified in the diagram, you can proceed to the process of laying the pipes of the heated floor circuits.

Laying heated floor pipes

• Work always begins with a thorough cleaning of the room - there should be no debris or dust on the surface of the base concrete screed. If this has not been done before, priming is performed with a deep penetration compound - this will strengthen and remove dust from the surface, and give it additional waterproofing qualities.
• A damper tape with a thickness of at least 5 mm is glued to the walls around the perimeter of the room. If the length of the room is more than 10 mm, the thickness should be increased based on:

h= L× 0.55 (h is the thickness of the compensation gap, L is the length of the room).

The height of the tape should correspond to the total thickness of the future floor, taking into account the screed and finishing coating + 5 mm.

• The next step is styling. Thin rolled material is laid end-to-end with the joints sealed with tape. When using EPS mats, they are joined with interlocking parts. If necessary, you can fix them to the floor surface with polyurethane glue. It is impossible to use adhesive compositions based on organic solvents - they will cause chemical decomposition of polystyrene.

• The joints between the laid mats are taped with waterproof tape. This step is not necessary when using profile mats - the locking system ensures the reliability of their pairing.
• If the EPS does not have an external coating, a layer of thin foil backing is covered (metalized layer up), with the joints sealed with tape.
• If flat mats are used, and the pipes are attached to the fittings, a metal mesh with cells of about 100 × 100 mm is laid. If mounting strips or plastic retaining brackets are used, the reinforcing mesh can be installed later by placing it on pads (stands) so that it is approximately centered between the pipes and the surface of the screed.
• It is advisable to transfer the layout of the contours to the laid out surface in accordance with the drawn up diagram and carefully check its correctness. A marking grid applied to some types of mats can be of great help here.
• One of the most difficult aspects is the correct laying of pipe contours. It is better to do this kind of work together - one unwinds the coil, and the other immediately fixes the coil with staples, between the bosses of the profile mat or in the mounting rails. The manifold cabinet usually leaves a margin of about 500 mm at both ends of the pipe.

Rushing in this process is disastrous - an incorrectly laid circuit (for example, an error led to an unacceptable intersection of pipes) is very problematic to redo.

• After laying the circuits according to the diagram and carefully checking its correctness, you can connect the pipes to the collectors using standard fittings. When making such an insertion, it is necessary to ensure that unnecessary stress is not created in the pipes (they cannot be connected “pull-in”), and that they themselves do not protrude above the surface of the planned screed.

Checking the integrity of the contours and filling the screed

• After the pipe circuits are laid and connected to the manifold combs, it is necessary to ensure that all connections are tight. To do this, the system is filled with coolant, sequentially each circuit through the supply comb, achieving complete air release, for which the corresponding valve is opened.
• The next step is hydraulic testing, or as they are more often called,
• Before starting crimping, it is recommended to temporarily remove air vents and plug the holes. Otherwise, they may fail, since they are designed only for a certain operating pressure.

The crimping process for different types of pipes has its own nuances.

— If metal-plastic pipes were used in the circuits, then the pressure in the system should be set to 6 bar. A pressure gauge installed in the manifold cabinet will allow visual inspection. If after 24 hours no pressure drop is recorded, the test is considered successful. If leaks are detected, the connections are tightened and the test is repeated.

— With cross-linked polyethylene pipes the process is somewhat more complicated. Initially, the pressure also rises to 6 bar. It inevitably begins to decrease due to the plasticity of the pipes, and after 30 minutes it should be raised again to the specified value. A similar cycle is carried out 3 more times. Then, after waiting another hour and a half, the pressure is again raised to 6 bar and the system is left for a day. A fall of no more than 1 is considered acceptable. 5 bar, but, of course, with a guaranteed absence of leaks.

• It is recommended to check the pipes in extreme temperature conditions. To do this, they are filled with hot coolant (with a temperature of about 80 ºC) with the same test pressure. A similar measure allows us to identify unreliability of individual fitting connections that require additional tightening. In addition, such heating will relieve excess stress in the pipes.

Once this is completed and possible identified deficiencies have been eliminated, you can proceed to pouring the screed. There is no need to drain the water from their system - this will protect the pipes from deformation that can occur from the pressure of uncured concrete. After the screed has set, the load will be evenly distributed, which will no longer pose a danger to the integrity of the pipes.

• It is best to use special compounds adapted specifically for heated floors. They contain plasticizers that ensure uniform filling without the formation of air bubbles (this is especially important when filling “difficult” places - near pipes, bosses of profile mats or mounting strips. In addition, the mixture contains microfiber, which creates reliable internal micro-reinforcement of concrete, increasing its strength under temperature changes.
• The screed is carried out in the usual manner - with the installation of beacons and guides to ensure the horizontal and evenness of the resulting coating.
• The maturation of the screed usually takes from 3 to 4 weeks, depending on the solution used. It is unacceptable to speed up this process by heating the screed with heated floor contours.

Putting a heated floor into operation is carried out only after the screed is completely ready. To do this, the entire system is brought back to normal condition, all removed elements are installed, connections are checked, and accumulated air is released.

You cannot immediately turn on the heated floor at full power - you need to give both the pipes and the screed time to gradually adapt. First, you should set the heating temperature to no more than 20 ºС. Every day you can raise it by 5 degrees, bringing it to the calculated level.

If everything is functioning normally, you can proceed to laying the final floor covering.

Video: example of installing a heated water floor system