Basement insulation with expanded polystyrene

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Basement insulation with expanded polystyrene
Basement insulation with expanded polystyrene

Thermal insulation of the basement with polystyrene foam plates, its features, pros and cons, preparation for insulation, methods of installation of the coating. Warming the basement with expanded polystyrene is an important measure, the purpose of which is to maintain a stable temperature and humidity level in its premises. For comfortable use in the household needs of the underground part of any building, these conditions are extremely important. We will tell you how to properly insulate the basement in this article.

Features of basement thermal insulation with expanded polystyrene

Basement thermal insulation with expanded polystyrene
Basement thermal insulation with expanded polystyrene

To create the required microclimate in the house, both heated and unheated basements are subject to insulation. In the first case, warming the basement with expanded polystyrene can significantly reduce the heat losses of the house, and in the second, it makes it possible to maintain a temperature of + 5-10 degrees in its buried part throughout the year and prevent the formation of vapor condensation on indoor surfaces in summer.

Especially at this time, the temperature of the outer part of the basement walls, in contact with the ground, becomes less than the "dew point". Therefore, when warm air enters it, all conditions are formed for the appearance of condensation and, as a result, the occurrence of mold and bad odor.

In the process of warming the basement from the cold, the ceiling, walls and floor are insulated. If it is heated, the floor does not need to be insulated, since the temperature of the upper part of the building will be maintained in its rooms. In an unheated basement, a five-centimeter layer of expanded polystyrene is sufficient to insulate the floor, which can be glued or fixed with umbrella dowels, followed by plastering the surface. The use of foam for the lower part of the building provides for a "warm floor" system.

Basement insulation must meet the following requirements:

  • To be resistant when working in a humid environment, while maintaining its thermal insulation properties;
  • Have the ability to withstand the pressure of the mass of soil from the outside, having sufficient strength for this.

These qualities, to one degree or another, are possessed by expanded polystyrene, which has become popular among builders, presented in two forms:

  1. Expanded polystyrene foam … This is a common foam, due to its low cost, it has a wide range of applications. Its disadvantages are low strength and ability to absorb moisture. In addition, thermal insulation made on the basis of this material often becomes a habitat for rats and mice. Therefore, when installing such a coating, it is necessary to provide for protective waterproofing for it, and periodically deratize in the basement.
  2. Extruded polystyrene foam … It differs from regular foam in its small, closed pores. This increases its strength and increases its hydrophobicity. Extruded polystyrene foam is more expensive, but it is also lightweight and does not rot or crumble. This insulation has higher indicators of biological and environmental safety, durability and thermal insulation properties. The strength of its slabs does not prevent the material from being easily processed to give the elements of the future coating the required dimensions.

Expanded polystyrene of both types does not differ in fire safety, and when heated, it has an unpleasant odor. To avoid fire insulation, it is not recommended to locate it near electrical wiring or sources of fire.

Advantages of basement insulation with expanded polystyrene and its disadvantages

Expanded polystyrene for basement insulation
Expanded polystyrene for basement insulation

The experience of thermal insulation of basements with expanded polystyrene indicates that even at a foundation depth of more than 7 m, it is reliable, regardless of the brand of this material and the duration of exposure to groundwater under pressure. When deciding to insulate the basement with extruded polystyrene foam, you need to know about its advantages and disadvantages in order to use this insulation as efficiently as possible.

The benefits include the following:

  • Basement insulation with polystyrene foam creates an excellent coating with low thermal conductivity.
  • The weight of the insulation is so small that it does not exert any serious load on the basement walls.
  • Compared to other methods of thermal insulation, protecting the basement from dampness and cold with expanded polystyrene will cost much less, especially since it will take a lot of material to insulate its walls.
  • Thermal insulation with a thickness of 100 mm is comparable in thermal conductivity to brickwork of a meter thickness.
  • After installation, the finished coating is not susceptible to aging, it is characterized by stability of shape and size.

The disadvantages of expanded polystyrene include, as already mentioned above, its flammability and release of toxic fumes when the material is heated.

Preparation for work on thermal insulation of the basement

Basement preparation for insulation
Basement preparation for insulation

Before insulating the basement, it is necessary to find out the characteristics of the soil on the building site. If its water saturation is higher than the norm, it is recommended to carry out drainage works in order to drain ground water from the underground part of the house.

The drainage system consists of drainage pipes with holes. They need to be laid alternately on a gravel pad, made with a slope of 3-5% below the base of the foundation. After installation, the pipes must be covered with washed rubble. During the operation of the drainage system, ground water seeping through the rubble enters the laid pipeline, through which it is then discharged into the sewer or into a separate well.

In order to prevent the pipes from silting up, the crushed stone bedding must be protected with geotextiles - a filtering material. It perfectly permeates water, retaining small particles of soil. Thanks to this filtration, the drainage system will not clog for a long time.

In addition to draining ground water from the basement, before insulating it, it is necessary to examine the condition of the buried part of the walls. First, they need to be cleaned of dirt or old insulation. If, after that, cracks and chips are found on the walls of the basement, they should be sealed with sealing mastic. All identified surface irregularities must be smoothed out with a cement mixture. Otherwise, the adhesion of the insulation plates to the basement walls will be loose.

Basement insulation technology with expanded polystyrene

Basement walls can be insulated from the inside and outside. Correct implementation of this procedure is guaranteed to save house owners from 5 to 20% of the money for paying for the coolant.

Basement insulation from the inside

The scheme of thermal insulation of the walls of the basement from the inside
The scheme of thermal insulation of the walls of the basement from the inside

Such insulation has a significant advantage - it retains heat throughout the house, including its basement. But, despite this, basement insulation with expanded polystyrene from the inside is not particularly popular. Internal insulation of its cold walls leads to the appearance of condensation on the insulated surfaces, which is actively absorbed by the insulation, causing the material to get wet and lose its heat-insulating properties.

Given these nuances, the procedure for isolating the basement from the inside can be divided into two sequential stages. Stage 1 is waterproofing, that is, a number of measures that help minimize the effect of moisture from the enclosing structures of the basement on the insulation. Means for protection against moisture can be PVC film or roofing felt, coating insulation with bitumen mastic or liquid rubber, as well as penetrating waterproofing.

Using lining insulation, it is possible to create an elastic layer up to 3-5 mm thick on the surface of the foundation walls. The application of the two-component mixture should be done with a stiff brush and the layer should be smoothed with a roller.

As for penetrating waterproofing, this is a set of procedures using compounds such as Kalmatron, HYDRO, Penetron, etc. For example, HYDRO-S is a mixture of sand, Portland cement and various chemical additives that impart special properties to the insulation: fast adhesion, water resistance, antifungal effect or versatility. Penetrating waterproofing forms insoluble crystals, which fill the pores and microscopic cavities in the concrete foundation. When using it, you must strictly follow the instructions of the manufacturer of the material.

In addition to protecting the insulation, it is necessary to provide for the possibility of removing excess moisture in the basement. To do this, it is necessary to leave ventilation holes in the basement of the house. With their help, natural air circulation in the basement is ensured and humid vapors are removed outside.

Stage 2 is thermal insulation. It includes a set of measures that guarantee energy savings in basement rooms, regardless of the thickness of its walls.

After waterproofing, the enclosing structures of the basement must be insulated with expanded polystyrene. To do this, its sheets with a thickness of 50 mm must be glued to the walls, starting from the bottom up. When the glue dries, you can make additional fastening of the insulation sheets with plastic umbrella dowels at the rate of four fastening points at the corners of the sheet and one in its middle. Such a measure will increase the service life of the thermal insulation coating.

The joints between the cladding elements must be filled with polyurethane foam. It should be borne in mind that the smoother the basement walls, the less voids will appear when installing the insulation between its slabs and the concrete surface of the basement walls.

After installing the thermal insulation, its surface must be strengthened. To do this, a reinforcing mesh should be fixed over the expanded polystyrene plates and covered with a layer of glue. After the composition has dried, the surface of the insulating coating must be sanded, and then plaster and paint to give it a finished look.

Basement insulation outside

Thermal insulation of the basement walls from the outside
Thermal insulation of the basement walls from the outside

External basement insulation is more effective than internal insulation. In this case, his task is not so much to keep the warmth in the house as to keep the cold outside the basement out.

Before starting the external insulation of the basement walls with expanded polystyrene, it is recommended to wait for good sunny weather, since it is unacceptable to apply insulating materials to a damp surface.

As in the previous case, the first layer of the coating is waterproofing. After installing it around the entire perimeter of the basement, on its walls, starting from the bottom, you need to glue polystyrene foam plates.

There are two ways to apply mastic on them: dotted and continuous coating. The latter method is more common. Its advantage is a glue that is evenly applied to the slab, which, after hardening, will serve as an additional protective layer, protecting the insulation from the destructive effects of soil conditions outside the basement walls.

The further process differs from thermal insulation from the inside. The deepened part of the basement walls must be treated with insulating mastic and the insulation from the soil side must be closed with drainage plates, after which the recess can be covered with soil, which will serve as an additional obstacle to the cold coming from the street.

The above-ground basement part of the basement walls, insulated with expanded polystyrene, must be plastered, and then finished with any suitable material on it.

How to insulate a basement with expanded polystyrene - look at the video:

When insulating a basement, do not forget about its drainage system and providing underground rooms with effective ventilation. This will help keep the insulation in working order.