Additional floor insulation: increasing the thickness of the insulation

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The need for additional insulation of the floor arises if in the cold season there is a feeling of discomfort. This is typical for the first floors, as well as in rooms above arches, spans and unheated rooms. Let’s talk about how to increase the thickness of the insulation in simple ways.

Additional floor insulation: increasing the thickness of the insulation

General features of floor insulation

If during construction work or during reconstruction the floors of the first floor were not insulated enough, then this error can be corrected.

In principle, floors account for a small fraction of the total heat loss. As practice shows, for the first floors no more than 15%. Of course, this figure is correct when all enclosing surfaces have normal thermal insulation..

Additional floor insulation: increasing the thickness of the insulation

But even more often, additional floor insulation is carried out as a measure that increases comfort. And sometimes you need just “a little” so that the bottom does not blow cold.

When choosing a method and heat-insulating materials, it must be borne in mind that floor insulation, unlike walls or a ceiling, does not just lead to a decrease in the useful volume. First of all, this will affect the height of the doorways, so at this stage you need to take into account two points:

  1. Entrance door sill height. In a private house it can be made by anyone, but in an apartment the height is limited to 25 mm (clause 3.23 SNiP 35-01-2001). For entrance doors, the standard direction of opening is considered to be outside (direction of evacuation in case of fire), but this is only if the door does not block the staircase and exits from other apartments when open. Therefore, in many “Khrushchevs” the entrance doors open inward. Increasing the height of the “pie” of the floor covering affects the height of the doorway, and this can interfere with the opening of the front door.
  2. Ventilation gap in the openings of interior doors between the leaf and the floor. For correct supply and exhaust ventilation, it must be at least 10 mm. And if additional insulation of the floor may not interfere with the operation of interior doors (swing or sliding with an upper rail), then the ventilation gap will probably almost disappear.

Additional floor insulation: increasing the thickness of the insulation

Considering the options for building up a floor insulation, you need to be prepared for two scenarios: a decrease in the height of the door leaf or an increase in the doorway.

The standard sets the height of the door leaf for internal doors 2000 and 2300 mm (GOST 6629–88). Domestic manufacturers also offer “intermediate” (non-standard) models in their product catalogs. Imported doors can generally have their own dimensions. In practice, the first scenario is possible if, after shortening, the leaf height is at least 2000 mm, and the materials and door structure allow this to be done. The same layouts are suitable for entrance doors..

Enlarging a doorway is much more difficult. First you need to remove the door, then dismantle the door frame and only after that “raise” the height of the opening. But this may be the only option if the canvas cannot be shortened (materials or sizes do not allow).

Additional floor insulation: increasing the thickness of the insulation

The very process of building up insulation is akin to carrying out cosmetic repairs to the floor covering. Depending on its structure and additional heat-insulating materials, the build-up can take place:

  • without dismantling the subfloor;
  • with the dismantling of the subfloor.

Features of additional insulation of floors on a screed

If the final floor covering was laid on the screed, then it is not dismantled. The floor covering is removed, and the insulation is built up over the screed. For this, you can use cork, plywood or fiberboard..

One of the most effective natural thermal insulation materials is technical cork. According to the manufacturing technology, it is an agglomerate of crushed bark of a cork tree. The structure is a cellular material with closed cells filled with air. Therefore, its thermal insulation properties are the same as that of expanded polystyrene, since both the structure and technology are the same..

Additional floor insulation: increasing the thickness of the insulation

But the mechanical strength, especially in compression, is higher for the cork.

There are two types of cork agglomerate: white and black. The thickness of white can be from 1 mm, black – from 10 mm. The thin cork agglomerate is produced in rolls. In slabs, it is made with a thickness of 10 mm and above.

Additional floor insulation: increasing the thickness of the insulation

Mount cork mats and slabs joint to joint, fixing to the base with glue.

Plywood or fiberboard in terms of thermal conductivity is approximately three times worse than cork agglomerate (plywood is slightly better than fiberboard). But they are also considered good thermal insulation materials. For comparison, their thermal conductivity is not worse than that of the lightest aerated concrete, on average half as much, which means better.

The installation of plywood takes place according to the standard technology of the sub-floor under parquet or parquet board. Sheets are cut into 4 parts, glued to the base on a special adhesive solution, additionally can be fixed with dowels.

Additional floor insulation: increasing the thickness of the insulation

In both cases, the thickness of the sheet wood insulation does not exceed 15-16 mm.

After the cork agglomerate or plywood has been laid, the floor covering is “put back” in place. And you can be sure that this will give a good result..

Additional floor insulation: increasing the thickness of the insulation

For better insulation, it is necessary to use traditional heat-insulating materials laid between the logs.

Additional insulation of floors on logs

The use of additional insulation between the lags can take place in three ways.

1. On concrete floors with lag installation. This is a common technology for installing new floors on logs, but already on a leveled and partially insulated concrete base. The difference is that laying the waterproofing layer is not necessary – it should already be included in the base. And the need for vapor barrier is determined by the nature of the additional thermal insulation. The thickness of the lag depends on the thickness of the insulation (plus a ventilated gap). The pitch of the lag and the need for a layer of plywood depends on the nature of the flooring.

Additional floor insulation: increasing the thickness of the insulation

2. Insulation of floors on logs without increasing the height of the log. One of the methods of additional insulation is the use of reflective insulation (penofol, foil-clad isolon, etc.). Such materials are quite often initially installed as additional thermal insulation in order to save on the thickness of the main insulation and not to take away the useful volume from the room. It may turn out that there is no such insulation in the subfloor, and the gap to the floor covering is sufficient for laying an additional layer, since usually heat-reflecting insulation has a small thickness.

Additional floor insulation: increasing the thickness of the insulation

3. Additional insulation with increasing the thickness of the log. The technology of increasing the height of the lathing is quite often used for walls and roofs when creating a ventilated gap. It is also called a counter-lattice. The same technology is used on the ground floor for wooden floors on logs, although its functions are slightly wider. The counter grill of the floor serves to fix the vapor barrier layer, create a ventilation gap and lay additional thermal insulation.

Additional floor insulation: increasing the thickness of the insulation

In fact, this is another level of timber, fixed perpendicular to the flooring of the main logs. Layout step – no more than 600 mm (determined by the size of the insulation and the nature of the floor covering), the thickness of the timber is from 50 mm, and the height is equal to the thickness of the additional insulation plus 20-30 mm for the ventilation gap.

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