Thermal insulation of building envelopes is an important stage in construction work. Most of the building’s heat loss occurs through walls (approximately 60–80%). Large losses mean high heating costs, which already "eats" up to 40% of utility bills. To prevent cost overruns during operation, you can do wall insulation with foam yourself.
Advantages and disadvantages of the material
Before deciding whether it is possible to insulate a house with polystyrene, you need to understand the features of this method. The material has some disadvantages that must be taken into account when designing. The following nuances are characteristic for wall decoration with foam:
- Polyfoam practically does not pass air. This material prevents the removal of wet steam from the room. Such a property can lead to a violation of the temperature-humidity regime. The problem can be solved using a forced exhaust ventilation device.
- Wall insulation with foam should be done using reliable waterproofing and waterproof facade. The considered insulation with simultaneous exposure to moisture and water crumbles into small balls. Styrene balls themselves do not absorb water, their permeability is very low. But in the space between them, moisture can easily accumulate. Typically, manufacturers are silent about this property, talking only about the hydrostability of the balls. When freezing inside the material, the water expands and leads to ruptures, the insulation of the facades with foam then ceases to fulfill its function. Reliable waterproofing will help solve the problem.
- Polyfoam has a low mechanical strength. When used in the construction of walls, this quality is not critical (as, for example, when laying in a pie cake), but it must be taken into account. If plaster is used as the facade finish, it is necessary to strengthen the surface with a reinforcing mesh. The best way out is to use polystyrene only as a component of a ventilated facade, for example, for siding.
The advantages of the material are not few. Carrying out the warming of the walls of the building with foam yourself, it is important to determine what qualities outweigh in each case. Based on the conclusions, they decide whether it is possible to use the considered method of warming the walls of private buildings.
Polyfoam is characterized by such advantages as:
- low price;
- simplicity of work;
- low mass of material;
- reduction in transportation costs;
- high heat-insulating indicators;
- safety.
It is important to remember that polystyrene is unstable to fire. When choosing a material, you should pay attention to the marking. Typically, materials have a fire resistance rating of G1 to G4. The lower the number in the marking, the better the foam resists burning. When choosing, you can also consult with the seller in the store.
We recommend reading an article about choosing a foam for insulation.
Warming a wooden house with polystyrene is not recommended. This is due to fire considerations as well as material properties. Wood breathes well, many choose it as the material of the walls precisely for this ability. Such decoration will become an obstacle to the air and with the slightest violation of construction technology can lead to decay of walls, mold and fungus. For a wooden house, it will be wiser to choose mineral wool as a heater. It has a high vapor permeability, therefore it will not interfere with the ventilation of the building.
Preparation of materials
Wall insulation with foam should begin with the preparation of tools and supplies. For work, regardless of what kind of finish will be used in the future (siding or plaster), you will need:
- polystyrene sheets or boards;
- starting profile to create support for the heater from below;
- construction adhesive for polystyrene;
- dish plugs or umbrellas.
Adhesive for working with polystyrene must be selected carefully. After using the wrong composition, defects can appear on the surface of the material, which will lead to a decrease in thermal insulation ability. The insulation is attached to an adhesive that does not contain any type of solvent. It is desirable that the packaging clearly says that the composition is suitable for polystyrene.
The length of the fasteners is selected depending on the thickness of the insulation and the material of the walls. In general, fixing the dowel must be at least 50 cm. For a concrete base, it is permissible to reduce the value to 40 mm, and for a brick wall, it is recommended to use the dowel 70 mm more than the thickness of the foam layer.
It is not recommended to use self-tapping screws and other elements for finishing with polystyrene for siding or plaster. They provide poor grip and can damage wall material.
Why is the material placed outside
The technology of wall insulation with foam from the outside is correct from the point of view of the construction science of heat engineering. The order of the layers is almost independent of the type of finish (siding, plaster or panel). Thermal insulation on the cold side is the right solution for several reasons:
- the useful area of the premises does not decrease;
- not only the internal volume is protected from the cold, but also the material of the external walls;
- the dew point (the border where condensation occurs) does not fall into the wall, it remains in the insulation.
Insulation of the house from the inside can only be done after justifying such actions. Reasons may include:
- a large building height when it is necessary to attract industrial climbers to perform outdoor work;
- the need to preserve the existing facade (for example, it has been completed recently, or work is being carried out in one apartment of an apartment building).
Stucco as a finish
This technology is called the wet facade. With proper execution of work, this option will reliably protect the house from the cold and will last for many years. The plaster is applied directly to the insulation. In this case, the work is performed in the following order:
1. Cleaning the walls of debris and dust.
2. Putty for leveling the surface. The fewer base defects, the lower the likelihood of damage to the thermal insulation layer. After completion of work, the evenness of the walls is checked using the building level or rule.
3. Surface priming to ensure good adhesion. The primer mixture should also have an antiseptic effect. This option will protect the building material from mold or mildew, as well as prevent damage by various microorganisms.
4. If plaster is used as the exterior wall decoration, the sheets must be fixed in a continuous layer without a frame. Pre-fix the sheets on the glue. In this case, vertical joints must be staggered. This means that each subsequent row relative to the previous one is shifted by about half the width.
After completion of work, the adhesive needs to allow time to dry. This takes about 3 days.
5. After the glue has dried, the insulation is additionally fixed with dowels.
6. The completion of the insulation works is the sealing of joints with foam. The excess composition is cut off after solidification and cleaned with a grater.
7. On the finished layer perform plastering in compliance with the technology and the use of reinforcing mesh.
We recommend that you familiarize yourself with this video instruction before starting work:
Warming under siding
If siding is used as a finishing material, it is necessary to provide a basis for its fastening. Unlike mineral wool, wall insulation with foam from the outside does not require a mandatory ventilation layer. Nevertheless, we still recommend using a ventilation layer - so the insulation will last much longer.
To know how to properly insulate a house with polystyrene foam for such material as siding, you need to familiarize yourself with the following procedure:
- surface cleaning;
- alignment of walls;
- priming;
- fixing brackets for installing frame racks for siding;
- foam bonding;
- fixing with dowels;
- laying a layer of waterproofing;
- installation of frame racks;
- after securing the siding.
Fixing with dowels, as in the previous case, is carried out after 3 days of drying. In the general case, the fixing technique does not differ from the previously considered case.
For a more detailed review, read the article on the external insulation of a house under siding.
The thickness of the insulation is assigned by thermotechnical calculation. For private construction, you can choose a thickness of approximately. On average, it is equal to 100 mm. The exact value depends on:
- climatic features of the construction site;
- wall material;
- wall thickness;
- the purpose of the premises (for residential, public and industrial, different requirements apply).
You can use the Teremok program for accurate calculations. It is presented on the network in the public domain. For the calculation, you need to know the composition of the wall and the thermal conductivity of the materials used. After calculation, the resulting value is rounded up.
Before you warm the house with foam, you must carefully select the material (density) and carefully study the technology for performing the work. Regardless of what is used for decoration (siding or wet facade), it is required to strictly observe the order of all layers and fix them securely. With proper insulation, walls and decoration will last for many years.