How to heat a room only with electric heated floors

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For 9 years, at almost every project a builder always appears who, with a smart look, convinces the Customer to save on radiators and heat the house with heated floors. The customer has doubts and is right. At first glance, warm floors are more comfortable, but is it convenient for heating? Let's figure it out.

Good afternoon My name is Alexey Goltsov . I am a design engineer, author of articles. Heating is my main specialty. I carry out projects for country houses, shops and restaurants. 20 projects for country houses a year

I mainly design for Moscow and the region. I'm leaving for the site.

You can order a heating project from me on the “Services” .

Why did this question arise?

No matter how funny it may sound: global warming and the view of Western countries are to blame.

The design temperature for heating in Moscow is –25°C for 5 days. This temperature has not been seen for many years, and customers of private houses began to share the opinion that radiators do not work, and therefore are not needed.

Warm floors cost 3 times more than radiators. Therefore, this opinion was picked up by builders and for the last 5-7 years they have been confidently advocating to abandon radiators completely.

But there are 2 nuances in this issue that they do not take into account:

How many years are you building the house for?

My Customers often say that their neighbor’s underfloor heating works successfully. But neither the Customer nor the neighbor takes into account the period of time.

If we are talking about the short term of 3-5 years, then radiators are really not needed in this case. But the house is being built for a longer period.

In building codes, heating is considered efficient if it heats the house for 50 years. For Moscow, the minimum temperature for 30-50 years is -25°C. And even if there has not been such a temperature over the past 5 years, this does not mean that it will not happen in the coming decades.

Therefore, as a specialist, I design a combined system of radiators and heated floors. We are obliged to provide radiators as a reserve so that the house does not freeze in the cold winter.

We don't need to "heat the house"

Heating a house is an incorrect term.

The whole nuance is that we must maintain a different temperature in each room. We need to heat each room separately. In the boiler room, garage, storeroom, it is enough to maintain +15°C. In the bedroom +23°C, in the bathrooms and bathrooms +25°C.

Indeed, if we calculate the house as a single space, a warm floor for heating is quite enough, but in practice we only need to heat those rooms that border on external walls and windows.

For example, internal corridors, halls and storage rooms in a 250 m2 house are often about 50 m2, but they do not need to be heated at all.

Thermal insulation of the house

The first thing you need to pay attention to when designing is the thermal insulation of your home. And the better the thermal insulation is, the lower the heat loss coefficient will be, and therefore the less energy will be required to maintain the temperature in the room at a given level. But thermal insulation of a house is not only insulation of the walls; it is also necessary to insulate the floor, and most importantly the ceiling. You need to turn your home into a comfortable “thermos” for living. There is a good thermos that keeps the temperature for a day, but there is also a bad thermos in which the water becomes cold after 5-6 hours. Same with the house. One house will cool down in 5-6 hours, and the other will be warm in a day.

Of course, the quality of thermal insulation materials is important. They should not lose their thermal insulation properties over time. And the expression: “the more, the better” will be right on point. The larger the thermal insulation layer, the lower the heat loss coefficient, which means your home will be like a “good thermos”. For example, it will be very good if the walls of the house, floor and roof are insulated with extruded polystyrene foam 100 mm thick or other heat-insulating material at least 100 mm thick.

Windows and doors are important elements in the construction of a country house. Poor quality and poor installation can negate all efforts to insulate the room. We will talk about how to choose the right windows and doors so that they do not turn out to be a “weak link” in article 8. I will take this information from a person who has been involved in window systems for more than 20 years. This will be the expert opinion of a “window” specialist.

Is it possible to abandon radiators and heat the house only with heated floors?

From the legal side

Answer: No, you can't. If you contact a large construction company with such an idea, they will refuse you. There are 3 reasons for this:

1) The heating system is designed for the lowest temperature. For Moscow this is –25°C for 5 days. If the average temperature stays at -25°C for 5 days, no heated floors will cope. More details: SP60.13330.2016 clause 5.13.

Minimum winter temperatures in Moscow

2) The temperature of the floor surface should be no more than 26°C, and for children's institutions 23°C. This is too low a temperature to heat a room. Radiators heat up to 80°C. I will tell you further what overheating of the surface leads to. More details: SP60.13330.2016 clause 6.4.8

3) Cold convection currents always come from the window. Radiators cover 50% of the window width, which helps reduce the cold air flow from the window. More details: SP60.13330.2016 clause 6.4.4.

From a practical point of view

Answer: Yes, it is possible, but is it convenient? Unfortunately, neither customers nor builders see all the consequences. The customer relies on the experience of the builder. The builder relies on the experience of past projects. That’s why there are so many speculations and fantasies on the topic of heated floors.

I will share these consequences with you.

Popular types of heating radiators

Aluminum

pros

• the most energy efficient type;
• low susceptibility to coolant;
• low susceptibility to corrosion;
• a light weight.

Minuses

• Suitable only for individual heating systems.

Heating radiator Global

Bimetallic

pros

• high heat transfer;
• increased strength;
• a light weight;
• neutrality to the chemical composition of the coolant.

Minuses

• high price.

Heating radiator Rifar

Steel

pros

• average energy efficiency;
• varied performance;
• fast warm-up;
• affordable price.

Minuses

• susceptibility to corrosion.

Heating radiator Purmo

What problems do you have to face when heating underfloor heating?

The house will not warm up before your arrival

Warm floors without radiators respond very slowly to any commands and changes. His inertia is too high.

First, the system will receive a command from the boiler, then it will warm up 45 mm of concrete screed, 20 mm of floor covering, and only then it will begin to slowly release heat into the room. The floor temperature is 35°C. Therefore, to heat the house from the standby temperature of 15°C to a comfortable 23°C, the heated floor will need approximately 11 hours.

Heated floor heating rate graph

If you do not plan to live in the house 24/7, underfloor heating will be uneconomical. When you are not at home, you will have to maintain not 15°C, but 20°C, otherwise the house simply will not have time to warm up before your arrival. Radiators will heat a house from 15°C to 23°C in an average of 3 hours.

No reserve in case of extreme cold

In a combined system, radiators turn on at an outside temperature of -12°C and work together with the heated floor.

Warm floors are needed for comfort. That is why it is “warm” and not “hot”. Heating a house with underfloor heating will not work in extreme cold.

If you decide not to install radiators, you are deprived of a reserve that is guaranteed to heat the house in extreme cold. In this case, you will have to overheat the floors and run across the floor. Overheated surfaces will emit odor.

According to calculations: an overheated floor can heat a room down to -16°C. At lower temperatures, the floors will not cope and the room will be cold.

Floor covering - tiles or porcelain stoneware

Underfloor heating imposes its own limitations on the coating material. Even small carpets on the floor will have to be eliminated throughout the house, because they completely block the heat flow.

Heat transfer from the floor surface directly depends on the coating material. You won't be able to afford parquet, laminate, PVC or cork. all this is not suitable for underfloor heating systems. Laminate and parquet transfer heat 7 times worse than tiles.

Important nuance : the internal composition of the material is not so important as the surface itself! Matte and ribbed surfaces of the same porcelain stoneware transfer heat 30% worse than smooth ones.

No floor-to-ceiling stained glass windows

Stained glass windows in rooms create large heat losses. About 50% larger than ordinary windows, so heated floors are not suitable for heating a house with stained glass windows. You will have to give up façade and stained glass windows in all living rooms.

It is permissible to heat underfloor heating in rooms with 1 or 2 regular windows. If the windows are stained glass, the warm floor will not cope.

A warm floor in a room with stained glass windows can heat the room at an outside temperature of at least -12°C, which is why in Europe warm floors are used as the main heating system. This is unacceptable in Russia.

Local hot spots or furniture with legs

With underfloor heating, the only source of heat is the floor surface. In bedrooms, furniture usually consumes 40% of the space. Sofas, wardrobes and beds completely block the heat flow from the floor to the air, so heat exchange does not occur and the room is not heated.

Therefore, there are 2 options for solving this problem: – sofas, wardrobes and beds must have legs; – local overheating zones along the windows.

Local overheating zones are the area of ​​the floor around walls and windows in which underfloor heating pipes are laid close to each other, with a reduced laying pitch, which results in an increase in heat flow.

Usually in bedrooms, the local overheating zone exactly falls on the area around the bed, so when you wake up on a frosty winter morning and get out of bed, you will definitely hit the hot zone of the heated floor with a temperature of 38-42 ° C, while without radiators the air temperature in the room will be about 18 ° C .

Connection diagrams for heating radiators

There are only 3 such schemes, each of them has its own characteristics, pros and cons.

Diagonal connection from 12 radiator sections

Option #1. Single-pipe

Here the radiators are connected in series, making installation much easier and requiring much less consumables. A pipe running under the radiators goes from the boiler through all the rooms and returns to it. The radiators are connected via lower pipes. The liquid fills the sections of the batteries, giving them heat, falls and goes through another pipe into the same pipe.

Video - Advantages of single-pipe heating systems

As for the disadvantages of the scheme, these include, first of all, rather low heat transfer, because the coolant in this case enters each battery after it has already cooled down. As a result, the further the room is from the boiler, the colder it will be.

Option #2. Two-pipe

There are 2 pipe circuits here at once - through one the coolant is supplied to the radiators, and through the other it is removed, due to which the thermal energy is distributed evenly throughout the house.

Note! This scheme has many advantages, since each individual room can provide its own temperature regime. And if repairs are required, there is no need to turn off the entire heating system. In a word, the scheme is much better than the one described above.

Video - Connecting radiators in a two-pipe system

About methods of connecting pipes to radiators

How effective such heating will be largely depends on the way the batteries are connected to the pipeline. There are several of these methods; let’s look at the features of each of them.

Table. How batteries are connected to heating pipes.

How to connect a radiator to pipes

A few more words about radiator heating

Due to the fact that heated air rises upward due to the laws of physics, the air temperature near the ceiling and next to the radiators can be quite high. In other words, heating will occur in areas that do not really need to be heated. But the floor temperature in this case will be only 16-17 degrees, that is, not the most comfortable for the feet. We conclude: with radiator heating, heat is distributed irrationally.

Operating principle of radiator heating

The air that passes through the batteries is warmed up and distributed throughout the room. Simply put, it circulates, and dust rises with it.

On a note! For radiator heating, it is very important to correctly calculate the number of sections for each device. After all, each section can heat only a limited area and the efficiency of the entire system depends on the number of sections in the batteries.

Video - Arrangement of a radiator heating system

When can you heat a house without radiators?

For this article, I analyzed the heating calculations of 20 cottages. For Moscow, the heating system is calculated according to standards for –25°C, St. Petersburg –24°C, Kazan –31°C, and only in the Krasnodar and Stavropol Territories, Rostov-on-Don and Crimea can it be heated with heated floors without radiators.

You can heat your house with underfloor heating when the outside temperature is not lower than -18°C.

Special construction region. Krasnodar region, Stavropol region, Rostov-on-Don and Crimea.

You do not plan to live in the house in winter. In the fall, you drain the water supply system and heated floors and close the house until spring.

Additional heat sources. Do you have a fireplace, stove or electric heaters?

Building with temporary use. Garage, covered gazebo, separate bathhouse. There is no point in maintaining a temperature of +23°C. In the most extreme cold, you will not be in the building, and the standby temperature of +15°C is sufficient. Warm floors will do.

Heat pump. Heating with heated floors is recommended by sellers of heat pumps. The heat pump does not prepare water at 80 °C - as needed for heating, but only 55 °C, which is optimal for a heated floor system. Radiators on water at 55°C will turn out to be huge.

What do we choose in the end?

There is no clear answer to the question - which heating is better: heated floors or radiators. Each device has its own advantages and disadvantages that must be taken into account when choosing.

If funds allow, and you are building a house for children and grandchildren, then the best option is warm floors. If you have a financial problem, you can give preference to radiators. After all, each system is capable of heating your home and creating a comfortable environment.

How much underfloor heating is needed for heating?

The issue of heating a house only with warm floors needs to be worked out at the stage of the architectural project. Rooms with stained glass windows cannot be heated with underfloor heating alone; radiators are required. But rooms with conventional glazing are quite suitable for underfloor heating.

To heat rooms only with heated floors, you need to deliberately increase the free area of ​​​​such rooms.

We know that 40% of the area is occupied by furniture, so we need to compensate for the missing space by combining rooms with adjacent rooms: combining a bedroom with a dressing room, moving the door to the corridor.

The formula for any type of house looks like this:

Spom – room area in m2 For a room with 1 window and a window sill Spom x 0.69 (69% of the floor) For a room with 2 windows on different facades Spom x 0.79 (79% of the floor)

For example , for a bedroom of 21 m2 with 2 windows, the required heated floor area is 21 × 0.79 = 16.6 m2. Furniture occupies 40% of the area, which is 0.4 x 21 = 8.4 m2. To heat such a bedroom with a warm floor, we need to increase the floor area by 16.6 - (21-8.4) = 4 m2. As a result, we need to expand the room by 1 m2 and add a dressing room of 3 m2.

Using this formula, you must first calculate the total area of ​​all bedrooms, and only then adjust the area of ​​the remaining rooms.

Which is better: heated floors or radiators?

For heating in autumn and spring - warm floor. In winter - radiators. Warm floors are a low-temperature system and respond slowly to weather changes.

In spring and autumn, the temperature difference between inside and outside the house is not as significant as in winter. Therefore, warm floors during this period, despite their slowness, are much better than radiators.

But in winter the picture is the opposite. In the house +23°C, outside -15°C. The temperature difference is huge. The cold flow from windows and stained glass penetrates into the room much more intensely than in autumn or spring. We need to stop these flows. Nothing can be better than radiators or convectors built into the floor.

Analysis of misconceptions

Uniform heating with heated floors. The temperature in the legs is higher, above the head – lower, and this is good, because... evenly and physiologically. Complete nonsense! Our task is to ensure not uniform, but rather local heating of the room in the areas of windows, external walls, corners, and street doors. We need to stop the cold currents from these surfaces.

Cost-effectiveness of heated floors?! How can a system that responds slowly to change be economical? The room became hot - and the warm floor will reduce power only after a couple of hours. Where are the savings?

Warm floors for allergy sufferers are complete nonsense! The phenomenon of “dry sublimation of dust” begins at temperatures above 90°C. The smell of dust from radiators comes only because they generally forget to wash them. In this case it has nothing to do with temperature.

Warm floors retain moisture. In winter, the air outside is dry by itself: 0.39 g/kg. In summer – wet – 10g/kg. Air humidity does not depend on the temperature of heated floors or radiators.

If there are misconceptions that I missed, write to me, we’ll discuss them and add them to the article.

The right project

The correct project must be the result of competent calculation. In the project, it is necessary to take into account not only the calculations made, but also take into account all the nuances of installing heated floors:

• Take into account the placement of stationary furniture;
• Do not exceed the length of the “threads” 80-100 meters;
• If necessary, plan several manifold cabinets;
• Plan the lengths of the contours with a length discrepancy of no more than 14-15 meters;
• The pitch between the pipes is planned according to the winter temperature in the region. 100 mm if the temperature does not fall below 22˚. 150 mm if the temperature in winter is relatively warm;
• The beginning of the contours in the heated floor laying schemes should first run along the external walls of the house.

Advantages of radiators

1. Installed under the windows . Windows are a source of rapid heat loss. The temperature outside changes all the time, which leads either to an increase in the cold flow from the window or to its decrease. The radiator smoothes out these flows.

2. No requirements for premises. Over the years, you can replace tiles with parquet, lay carpets, install monolithic furniture and not depend on the requirements for heated floors.

3. No overheating areas that are uncomfortable to walk on.

4. No odors from furniture or carpets. Warm floors heat up the furniture. There is a smell coming from the furniture.

Types of heated floors

Warm floors are divided into water and electric:

1. Water - consist of flexible pipes through which coolant heated to 30 - 35 degrees moves. The highway laying pattern can be “snake” or “snail”. Most often they are mounted under a cement-concrete screed. Although, if there are wooden floors, installation is possible without pouring concrete.

• Electric heated floors are:
• cable - this is a wire that can be located under any surface, laid in a screed or between insulation bosses;
• mats - also a cable type of construction, only the wire is already fixed on the substrate (mat) with a certain pitch;
• infrared is a film with built-in carbon plates, no screed is required, the installation process is simple and quick.

Conclusion

Each house is too individual to promise anything without calculations. It is possible to heat a house with underfloor heating, but this issue needs to be discussed at the stage of the architectural project.

Combine bedrooms with a dressing room, increase the area of ​​the rooms due to corridors and moving doors. Conceptually, you need to think through each room separately.

A house without a project is just “savings”.

If you find a company that easily answers this question, I advise you to doubt the competence of these people. The issue is complex and requires a thoughtful approach.

If you don’t have time to experiment with the heating system, or don’t have extra money for constant improvements, I recommend calculating the heat loss of the building, or better yet, designing a heating system and heated floors.

You can order a project from me in the “Services” . Based on calculations, we will be able to select the right radiators, pipes and find out the exact cost of equipment and installation work. We will be able to understand which rooms can be heated with underfloor heating and what architectural modifications are needed for this.

Preliminary project cost calculator

Thanks for reading! For the design of engineering systems, please call or email [email protected]

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Comments

1. Leonid:
   06/01/2020 at 17:23

   In practice, 3 houses are fully heated with underfloor heating, everyone is happy. You have too many pros and cons.

   Answer

   Goltsov Alexey:

   02.06.2020 at 15:57

   Leonid, Good afternoon. Thank you for your attention. An excellent phrase: “In practice, 3 houses are completely heated with underfloor heating.”

   1) What do you mean heated? At what temperature? At -10°C - is it “heated”? and at -25°C? Professionals don't talk like that. According to the standards, “houses are heated” at -25°C for 5 days for Moscow. This temperature has not been seen for a long time. I suspect that you are misleading me.

   2) What does completely mean? — My sofa is near the window, the guests are sitting with their backs to the window. In the morning they complain - “the back is blown.” Is it complete or not complete? or is the guest to blame? or is the owner a fool? And the Code of Rules SP 60.13330.2016 - are we violating because we come up with our own rules? Is that how it works?

   3) The house will be warmed up with warm floors from 12 degrees to 23 for 11 hours. This is a minus that outweighs all the pluses.

   Answer

2. Alexander:

   01/18/2021 at 10:06

   I will be very surprised if my post gets approval)) But the author must be able to admit his mistakes.

   Answer

   Goltsov Alexey:

   01/18/2021 at 14:38

   Alexander, Good afternoon. There is no need to treat people as idiots. I really won't post your messages with an advertising link.

   You are involved in heat pumps. Radiators don't work with a heat pump, so you're left with underfloor heating. Your income and the well-being of you and your family depend on it.

   For my readers: - Alexander wrote that heated floors are 20-30% cheaper than radiators. — Local overheating zones are not dangerous. I didn’t specify what exactly is not scary. — Stained glass windows and heated floors are combined within reasonable limits. He did not specify where reasonable limits begin and end. — Sent the video to my resource

   Answer

3. Ulvi:

   04/25/2021 at 21:00

   I don’t even know what to say, but I was working in such an office, sitting all day in a huge room of 150 square meters, even more, and there was only a warm floor. It was very hot, even stuffy in winter. But in our street the maximum temperature is -2

   Answer

   Goltsov Alexey:

   04/26/2021 at 13:23

   Ulvi, the floor area of ​​an office space is much larger than the area of ​​the external walls and windows; if you have a single room of 150 m2, then underfloor heating is possible. My article about underfloor heating for private homes.

   Answer

4. Robert:

   13.12.2021 at 17:36

   Alexey, hello! Being a civil engineer, I generally share your professional approach to the issues of heating private houses and, in particular, the possibility of using heated floors as an addition to the main heating with radiators for most of our climatic conditions. I would like to add the following (you are talking about this, I want to strengthen it): floors made of any other materials, taking into account their components (with the exception of stone and ceramic tiles), will smell of “chemistry”, no matter what environmental certificates are presented. I intend to order you a project or a fundamental solution to complex heating issues (radiators + heated floors). I would like to get your opinion on the composition of the plank floor structure with joists on a reinforced concrete screed on the ground. In this case, how to organize additional floor heating solely for comfort. Ekaterinburg Sincerely, Robert

   Answer

   Goltsov Alexey:

   01/10/2022 at 18:29

   Good afternoon, Robert. I will write a separate article about floor pies on joists, on the ground, etc. There's simply not enough time for this. There are standard pies for these occasions. For example, Vladimir Sukhorukov “heat-water” popularly talks about them. I know Vladimir personally. Everyone should be good only in their professional role. He is a good installer (not a designer). Watch his video on the channel.

   Answer