How to make a warm floor in a wooden house

Recommendation points

• What is the main difficulty
• Common flooring systems
• Thermal cutoff solution
• Electrics or water heating
• Features of using heating wire or tubes
• Suitable types of flooring

Underfloor heating in a wooden house is difficult for a number of reasons. The two main options for implementing such a solution are electric heating films and pipes for water heating systems. Today we will consider the features of the device and installation for each type of underfloor heating in a wooden house.

What is the main difficulty

Few would deny that the simplest option for a warm floor is a concrete floor on the ground. In wooden houses, this method of device is rarely implemented, basically, you have to deal with the floor on logs or frame systems. The main disadvantage is the high heat capacity of wood: it is able to absorb a significant proportion of heat and transfer it from the outside, that is, to the soil or subfloor.

In such an environment, a warm floor cannot be ergonomic and convenient to set up. The inertia of the system increases above the norm, moreover, the heating of the soil under the house does not fit well into the concept of energy saving and resource saving.

The amount of heat that the underfloor heating system is able to accumulate is rather strictly regulated by the project for its device. The only simple way to ensure proper heat accumulation is a sand concrete screed. It has several goals:

1. Protection of heating elements from damage;
2. Heat accumulation to smooth out the cyclic operation of the boiler;
3. Aligning the heat zebra when using cord or tubular heaters.

Due to its high thermal conductivity, the concrete screed evenly transfers heat from the heated pipes of the underfloor heating to the floor covering. 1 – wooden logs; 2 – rough floor; 3 – sheathing with sheet material; 4 – thermal barrier with a heat-reflecting screen; 5 – reinforcing mesh; 6 – concrete screed; 7 – tubes of a water heated floor; 8 – finishing floor covering

In order for the warm floor to heat exclusively the interior space of the house, a thermal barrier is provided. Without it, the warm floor turns into a huge radiator that heats the outside environment. This is the main difficulty of installing a warm floor in a wooden house. A plank floor is not very suitable for placing a multi-layer coating, it is even more difficult to ensure long-term and problem-free operation. The good news is that technical solutions to most of these problems have long been found, and we will study them..

Common flooring systems

For the installation of insulation and pouring the screed to the subfloor, the main requirement is presented – it must be rigid, little susceptible to warping, shrinkage and displacement. This is done in different ways depending on the flooring system..

When working with the floor on logs, the main obstacle is a rather high distance between them. With a significant thickness of the board, the upper plane is constantly bent at different times of the year; the screed cannot be securely fixed on such a basis. In this case, the contraction of the surface with sheet materials is practiced, which excludes the formation of local displacements that cause flaking of the concrete mass. At the discretion of the developer, the flooring can be carried out either above or below the thermal barrier..

With a frame device of the floor, numerous and often located stiffening ribs ensure the immobility of the entire plane. Reinforcement of the sub-floor is required at an estimated operational load of less than 100 kg / m², in other cases, the screed can be poured directly over the boardwalk. The recommended step for installing frame elements under a warm floor is 35-40 cm with a board thickness of 25 mm.

Thermal cutoff solution

Even with a heating device on top of an insulated frame floor, localization of the heat source from numerous cold bridges is required. However, the cutoff can be represented by rather thin sheet materials (20–30 mm) made of foamed polymers. Traditionally, leaders in this context of use are:

1. EPPS – cheap, but sensitive to overheating;
2. PPU is more expensive, but absolutely chemically inert;
3. PIR is an analogue of the previous material with higher requirements for fire safety.

If the thermal cut-off is laid on top of the floor sheathing, it must be glued without fail. For this, universal adhesive mixtures are used: Ceresit CT 85, GEWEBEKLEBR, BOLIX ZW, “Polimin” and the like. If the sheet flooring is made over the thermal cutoff, it is enough to press this cake to the subfloor with self-tapping screws, one for every 80-100 cm². Cold bridges made of such fasteners are rather weak, and the fixation of the surface under the screed is strong and very reliable.

Electrics or water heating

There is an option for installing a warm floor on a wooden base without pouring the screed. This is rather an exceptional case, since the technology is designed for zone heating. There are also significant differences in installation technology.

In this embodiment, the function of heat accumulation is performed by the sheet flooring. Thermal insulation must certainly remain under it: if not a full-fledged 25 mm of polymeric foam board, then at least 7–8 mm of foamed roll polyethylene. But the screed over such a floor is not poured, this does not allow a special type of heating elements.

We are talking about the underfloor heating film system. We draw your attention to the fact that the film is used for zonal floor heating: the inertia of heating is minimal, but the heat loss is also slightly higher. Mostly film heaters are placed under linoleum, laminate and carpet. If the coating requires a soft backing device, it is placed under the heating elements, but never on top of them..

Another option for electric heating has a lot in common with a water floor heating. Basically, the installation technique is similar: both cables and tubes are attached to the installation subsystem in the form of a comb or punched tape, then they are necessarily filled with a tie. This requirement is justified by the need to distribute heat from linearly laid heaters evenly over the entire surface. In general, the distance between the turns of the heating tubes or wires is 10-15 times the thickness of the screed. It is necessary to have a hydro-barrier that prevents the screed from dehydration before hydration is complete, but in most cases this requirement is quite easy to fulfill with bitumen mastic. When pouring a screed over the sheet sheathing, under the latter, you can spread a plastic film and glue the joints.

Features of using heating wire or tubes

The choice between water pipes and heating cable is not always made only for the available energy sources. As an example, electricity can heat both the floor itself and the liquid heat transfer agent circulating inside it..

Electrical heating cords, especially self-regulating ones, are preferred for high temperature accuracy. The heating time of the coating when turned on is also higher. The main disadvantage is the inability to provide a sufficiently high power of the electrical connection.

When using a water pipe system, there is no risk of local overheating, unlike electrical systems, which could cause warpage of the wooden base. Underfloor heating in a wooden house is an unstable system that requires special attention. Situations such as breakdown or rupture of tubes must be avoided by all means. The heat exchangers themselves are necessarily made of high-quality and certified materials.

Suitable types of flooring

In truth, a high-quality warm floor is a godsend for any flooring seller. In addition to the fact that a perfectly flat plane can be brought out with a screed, soft heating provides practically “incubator” conditions for the operation of floor finishing.

Basically, the installation of a warm floor is recommended when covering with carpet or other washable carpets. The remaining moisture from the washing vacuum cleaner quickly evaporates, which is why even thick pile remains almost sterile for a long time.

Permanent heating also has the best effect on linoleum and laminate flooring. The temperature of the underfloor heating is not enough to dry out, while the linoleum is guaranteed not to lose its plasticity as a result of hypothermia, and the laminate will not have a hint of play in the locking joints.