Insulation For A Warm Water Floor: Types, How To Choose, Methods Of Laying

Are you installing a water underfloor heating system in your country house and the time has come to install a thermal carpet pad? Agree that among the variety of proposals of insulating materials offered by manufacturers, sometimes it is not easy to make the right choice.

We will help you determine which insulator for warm water flooring is better. Together with you we will understand all the subtleties of assembling thermal insulation systems. We will study the characteristics of popular materials, assess the key advantages and disadvantages.

Self-employed home masters will find installation instructions with us. To facilitate orientation in the range offered by the building material market, we have selected clips with recommendations on the choice of insulation and laying.

The contents of the article:

  • The need for system insulation
  • Types of insulation under a water heated floor
    • Option #1 - thermal insulation boards
    • Option #2 - profile systems with rails
    • Option #3 - roll heat insulation
  • Pecifics of installing insulation
    • #1 - technology for laying boards
    • No. 2 - installation of roll materials
    • No. 3 - scheme for installing mats
  • Conclusions and useful video on the subject

The need for system thermal insulation

Any instruction for the installation of water heated floor for self-masters specifies that insulation must be used.

The insulation layer in the arrangement of the water floor has several important functions. It not only helps to heat the room evenly but also as a heat shield it allows a considerable reduction of the system's energy losses.

The floor screed laid over the insulation layer becomes a one-piece heat-transferring element with a large surface area.

Insulation for a warm water floor: types, how to choose, methods of laying

The main purpose of the insulation layer is to spread the heat in the heated room evenly preventing heat leakage through the floor slabs

The even distribution of energy makes the orderly convection heat flow in one speed and direction. As a result, evenly distributed heat waves will not create cold and hot spots on the floor, creating the most comfortable conditions for the households.

In addition, by directing the warm air streams in the same direction, energy costs for system operation can be reduced while keeping its power unchanged.

Modern heat insulation mats are equipped with handy bosses with which the pipes can be laid quickly and still be fixed.

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Former roll soft and rigid board materials are used for the construction of the heat insulation layer under the water underfloor heating systems. Rolled ones are easier to install, but are less effective in terms of thermal and technical criteria

Extruded polystyrene foam, the structure of which virtually eliminates moisture absorption and retention

Organization of the insulating component of the floor system from non-extruded polystyrene foam, i.e.

The easiest and most convenient variant of insulation is now polystyrene boards with convex relief, The simplest and the most convenient variant of heat insulation are nowadays polystyrene boards with a convex relief, within which it is not possible to maintain the calculated pitch when laying, thermal insulation for pipes is used,

Tile carpet pad for underfloor heating

PVC foam insulation in laying

Insulation foam insulation

Foam boards with factory markings

Polystyrene insulation with bosses

Installation of pipes with the required pitch

Forming the distance for the dry stacking

Applying foam plastic for pipes

Views of underfloor heating insulation

There are many variations of underfloor heating insulation in the current market. The choice of substrate thickness is limited only by the owner's material possibilities and the technical parameters of the room.

All thermal insulation materials prevent sound waves from moving through their thickness, and are therefore characterized by high sound absorption values.

Insulation for a warm water floor: types, how to choose, methods of laying

If there is a heated room under the basement, insulation of 10-12 mm thickness is sufficient; if there is a basement or ground, a substrate of 30 mm or more is required

Independent on the version, the thermal insulation material has special requirements:

  • it must have a low thermal conductivity coefficient;
  • take the load created by water-filled pipes;
  • take the load of the screed laid over the pipe;
  • it must be resistant to dynamic influences that may occur during operation of the system, and after pressure reduction it must take its original shape.

The desired effect can be achieved by using thermal insulation material with a density of at least 35 kg/m3.

Option #1 - thermal insulation boards

In premises where the ceiling height is 260 centimetres or more, rigid polymer based thermal insulation can be preferred.

Foam or polystyrene foam. The basis for the production of thermal insulation boards can be foam or polystyrene foam.

The first version is created by non-extrusion, between its polymer cells there are channels for the passage of air and vapor. Styrofoam has a low specific weight and high vapor permeability.

The extrusion method is used in the production of expanded polystyrene, due to which the cells of the material are firmly sintered by the walls with each other. The vapor permeability of the insulation is practically zero. On the other hand, it has high strength and the ability to withstand considerable mechanical stress.

The specific heat capacity of expanded polystyrene is somewhat higher than that of plastic foam. In the first case it is 1.34 kJ/(kg°С), in the second it is 1.26 kJ/(kg°С). The difference is not great, but the calculations can have a noticeable effect on the total thickness of the floor heating system.

Standard size of Penoplex insulation sheets, for example, 120 cm × 240 cm. GOST number 15588-86 regulates the width from 50 cm to 130 cm, the length from 90 cm to 500 cm.

The density of polystyrene foam is 150 kg/m³, the same characteristic of foam is 125 kg/m³. Depending on the specific production process and the properties put into the product by the manufacturers, the characteristics of the materials may vary.

Insulation for a warm water floor: types, how to choose, methods of laying

Thanks to its unique composition polystyrene boards act as good soundproofing and their allowable load is about 50 kN/sq.m

When comparing the two types of material, the foam is unprofitable because it is inferior to the extrusion product in terms of density. Due to this, it is less resistant to deformation under mechanical loads.

This significantly reduces its thermal insulation properties. Styrofoam is recommended to be laid in floor structures between the joists.

Cork. It is not uncommon to use cork as an insulating substrate under water and electric floors. Due to its special structure, which are miniature prisms of regular shape, cork insulation is characterized by considerable compressive strength, as well as the lack of adhesion to cement mortar.

In view of the high cost of the material, cork coating is often chosen for residential areas in which the base is already well insulated. Otherwise, in order to achieve the desired effect it is necessary to purchase at least 30mm thick technical cork, which may be very expensive.

Insulation for a warm water floor: types, how to choose, methods of laying

The main advantage of cork mats made of several layers of glued cork oak bark fibres is the environmental compatibility

The only drawback of cork mats is that they are hygroscopic and also produced as one-part thermal insulators. Therefore, when installing them, it is necessary to use additional layers that will provide vapour and water protection.

Mineral wool. As an alternative affordable option - the use of mineral wool. It comes in the form of flexible mats or hard boards.

Since mineral wool crumples under the weight when laid in a screed, which negatively affects its thermal protection properties, this material is also better combined with decking structures assembled from wooden lag.

Insulation for a warm water floor: types, how to choose, methods of laying

With mineral wool as an insulating layer, the heat output of the water underfloor heating will be maximal

The only drawback is the foam core that is hazardous to human health and the low water resistance. But properly performed waterproofing easily removes these drawbacks.

Option #2 - Profile systems with rails

Forming systems help make the installation of water circuits easier. They are made by means of hydrofoil pressing technology resulting in shaped projections.

There are two types of products: mounted and laminatedwhich are covered with a vapour barrier film.

Insulation for a warm water floor: types, how to choose, methods of laying

Hatches or guide grooves are located on the surface of the profiled mats in straight rows in which heating circuits can be easily fitted

The base material is extruded polystyrene foam created by forcing a molten mass through the holes of an extruder.

The polymer base is famous for its resistance to moisture and high mechanical strength. The thickness of the board itself can vary from 10 to 35 mm. The main thing is that it must be in proportion to the thickness of the screed.

The side edges of each board are fitted with locks which allow a perfect interlocking of the elements, forming a continuous field devoid of thermal-acoustic joints.

The height of the cylindrical projections on the surface of the boards is 20-25 mm. This is enough to comfortably place and securely fix water circuits with a diameter of 14 to 20 mm. The tightly fitted rows of bosses prevent the possibility of the stacked contours shifting during the grouting process.

Insulation for a warm water floor: types, how to choose, methods of laying

The only drawback of the profiled systems is that it is impossible to fit water circuits made of pipes with a non-standard diameter into them

A special feature of the assembly of profiled systems is that once the water circuits are fitted, the structures are filled with a small layer of glue compound from above. Only after a day or two, when the adhesive has dried completely, the system is put into operation.

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Polystyrene boards with bosses

Lock on edge of thermal insulation board

Forming a smooth pipe bend angle

Heated floor assembled

Option #3 - roll heat insulation

Roll heat insulation is chosen for rooms where the distance to the ceilings is critical. By using thin foil layers with a protective lavsan coating, the thickness of the \"pie\" can be significantly reduced. The maximum thickness of such substrate is only 9-12 mm.

Insulation for a warm water floor: types, how to choose, methods of laying

The foil layer applied on one side of the insulation is good at reflecting heat radiation, thus preventing energy loss

Foil insulation is equipped with a heat reflective lavsan or thermal insulation jacket. Thin metallized materials perfectly reflect heat rays, so you can safely reduce the thickness of the insulation without fear of reducing the insulating qualities.

An important requirement when using foil options is that materials with aluminum foil cannot be used in the construction of floors with a cement-sand screed. The alkaline environment of the mixture during pouring will simply corrode the aluminium layer.

However, if a protective foil is placed over the foil, laying is possible. Use is permitted if the mortar is mixed with gypsum and not with cement powder. Some manufacturers replace the foil layer with lavsan or polypropylene film by adding metallic inclusions.

Insulation for a warm water floor: types, how to choose, methods of laying

In an effort to facilitate the installation process, many manufacturers put a special marking on the foil side of the produced roll materials that acts as a guide for laying the heating circuit

The downside of foil materials is that they reflect heat well but do not insulate well enough. If the floor is laid over the basement room, thin roll solutions are not enough.

Some craftsmen solve the problem by laying rigid insulating mats in two instead of one layer. But in doing so, the sheets are placed in such a way that the seams of the lower substrate overlap the seams of the upper one. This allows to minimize heat loss.

Peculiarities of laying insulation

The scheme of installation of the carpet pad depends on the type of materials used. But in any case it is necessary to place it on the most even surface.

No. 1 - Laying technology of the boards

The carpet pad assembled from the boards with mounting chamfer is easy - just like a construction set. The boards are easy to fit and measure. It is possible to cut the boards to size with an ordinary knife.

The carpet pad is easy to install because the contours and the length of the pipes can be changed at any time during installation. To prevent the material plates from shifting relative to each other during installation and operation, their joints are sealed with construction adhesive tape.

Insulation for a warm water floor: types, how to choose, methods of laying

In order to prevent the formation of thermal bridges the contour joints between the boards adjacent to each other are sealed with foil tape

Following steps for installing the insulation boards:

  1. Foam boards are laid on a cleaned and leveled base, securing them with special plastic staples, anchor dowels or planting them on an adhesive compound.
  2. Foil layer is laid on top of the laid and docked boards.
  3. The top layer is covered with a reinforcing mesh on which the pipes are subsequently mounted.

If the concrete screed of the base floor has been poured with considerable deviations from the level or has rough cracks and unevenness, or if the concrete slabs have been laid with irregularities, before laying the underlayment it is better to construct a frame. To do this, dry and level wooden joists of 50x50, 50x100 or 100x100 mm cross-section are assembled.

Insulation for a warm water floor: types, how to choose, methods of laying

The joists are placed 60 cm apart and mineral wool or foam board pieces are inserted between them

The distance of 60 cm between the joists is the best option as this \"step\" does not require additional purlins. The main thing is to keep the joists in the same plane and level.

The insulation boards must be laid tightly between the wooden joists. If there are gaps, they must be filled with installation foam.

There are some nuances to be observed in the installation of extruded polystyrene boards:

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Laying extruded polystyrene boards

Laying on the principle of masonry

Setting the damping tape around the room

Waterproofing with Factory marked installation

No. 2 - Installation of roll-up material

Lay the roll-up material on a carefully levelled base and fix to the substrate with tile adhesive or double-sided adhesive tape. Strips should be cut to the required size with ordinary office scissors.

In order to compensate for the thermal expansion of the screed, it is recommended to place the foil layer with a slight overlap onto the wall.

Insulation for a warm water floor: types, how to choose, methods of laying

The foil material is placed with the metallic side facing up in such a way that the metallized surface provides the best heat reflection

The markings on the printed assembly markings are used as a guide when installing the roll materials. It defines the distance between the contours and facilitates the laying of the pipes. Rolled materials usually have an allowance of foil polymer film at the edges to allow for the connection of adjacent webs.

When laying the cuts, special attention is paid to temperature seams. To this end, the joints of the laid strips are glued with one-sided construction or metallized adhesive tape. If cork is used as the carpet pad, a reliable vapour and water insulation must be ensured prior to its laying.

¹3 - Layout of mats

The step prior to laying mats is to arrange a film waterproofing membrane. After it has been laid, strips of damping tape are glued around the perimeter of the room along the bottom part of each wall.

Lay the mats on the prepared base and fasten the boards together using a locking system. In order to securely fasten the thin and lightweight boards, adhesive bonding and the use of plastic hooks are used.

Insulation for a warm water floor: types, how to choose, methods of laying

Some manufacturers, for the convenience of installation, enclose edge strips with the mats that allow convenient marking of areas leaving the heating zone

an important point: metal fasteners must not be used when installing the mats as they may damage the integrity of not only the thermal insulation, but also the waterproofing.

Choice of the best substrate for a thermal insulation carpet pad depends on your capabilities. Yes, a good carpet pad will not be cheap. But it will significantly increase the functionality of the arranged water floor system.

Conclusions and useful video on the topic

Video #1. Choosing insulation under a cement screed:

Video #2. A visual example of laying mats:

Video #3. Installation of roll insulation:

To make the right choice for underfloor insulation, follow the technical specifications of the room, taking into account not only the thickness of the product but also the maximum compressive load.

With the right approach to the choice of thermal insulation and observing all the details of installation, you can create a reliable basis for the arrangement of a functional water underfloor system.

Would you like to tell me about how you chose and laid insulation under the heating floor in your home? Have questions or valuable recommendations? Please write your comments in the box below.

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