Calculator for calculating the thickness of the foundation insulation. Thermal insulation of a stone house: basic principles of construction and calculation of the thickness of the insulation Measurement of the insulation of the foundation outside with expanded polystyrene calculator

With this calculator determine the load on the foundation strip and the width of the foundation base.

• dimensions of vertical and horizontal thermal insulation;
• the thickness of the soil cushion.

Initial data:

• As a heat insulator, we accept thermal insulation boards made of extruded polystyrene foam (XPS) grade 35;
• Material for the device of a soil cushion and filling the sinuses of the excavation - crushed stone with a density R= 2040 kg / m3 and modulus of deformation E= 65000 kPa.
• The base soils are represented by silty sands with a density R= 1800 kg / m3 (18.0 kN / m3) and modulus of deformation E= 18000 kPa.

Calculation sequence:

Step 1. Definition of IM. We find the specified parameter for the construction site (Smolensk) according to the schematic IM map (see below). IM = 50,000 degree hours.

Step 2. Determination of the parameters of vertical and horizontal insulation.

In table 1, the following thermal insulation parameters correspond to the frost index IM = 50,000 degree hours:

• vertical insulation thickness by= 0.06 m;
• thickness of horizontal thermal insulation along the perimeter of the building bh= 0.061 m;
• thickness of horizontal insulation at the corners of the building bc= 0.075 m;
• insulation skirt width Dh= 0.6 m;
• the length of the sections near the corners of the building Lc= 1.5 m.

Step Z. Calculation of the thickness of the soil cushion.

The thickness of the soil cushion for heated buildings with an air temperature in the premises in winter not lower than 17 ° C is taken at least 0.2 m.

Answer. Based on the calculation performed, we finally accept:

• the thickness of the vertical thermal insulation of the slabs by= 0.06 m;
• the thickness of the horizontal thermal insulation along the perimeter of the building made of slabs bh= 0.061 m;
• the thickness of the horizontal insulation at the corners of the slab building bc= 0.075 m;
• the width of the insulating skirt Dh= 0.6m;
• length of sections near the corners of a building with reinforced thermal insulation Lc= 1.5 m;
• the thickness of the soil cushion is 0.2 m.

In this case, the depth of the pit under the TFMZ will be: 0.4 m + 0.2 m = 0.6 m.

Frost index on the map

Fig. 1. Frost index

Frost index (MI): the absolute value of negative degrees of outdoor air with a 1% coverage or the occurrence of an event with a probability of once every 100 years.

The frost index with such security is not used in construction practice on the territory of the Russian Federation. Such security is due to high requirements for the durability of foundations. With reduced requirements for the durability of the foundation, it is possible to take the value of the IM provision of 2% (the occurrence of an event with a probability of once every 50 years).

The required MI values ​​are obtained by special calculations. For approximate calculations, the value of the MI can be taken according to the schematic map shown on Rice. 1 Watch!- all polls

If the floors in the house are not insulated, then there is no insulation that serves as a barrier between the ground and the floor itself. Thus, the soil under the house will serve as another heat accumulator, and its temperature at the base of the foundation will be higher. To calculate the foundation, you can use the foundation calculator.

If the floor is insulated in the house, then this insulation will serve as a barrier to heat and will not allow the heat to be spent on heating the soil. This causes a lower temperature under the house and foundation, which makes it freeze faster. Therefore, with this option, the thickness of the insulation should be greater.

The thickness of the permanent insulation in the basement floor, the foundation.

In the table below you will see the result of the calculations of the main insulation materials with the following data: the base of the house is a reinforced concrete monolithic slab 150 mm thick; the floor is lined with a 35 mm grooved board; the technical underground is designed in 2 versions - with sand backfill and ventilated. Online calculator for calculating the weight of reinforcement for strip foundations.

In the modern world, there is a large selection of materials for basement insulation. Many people believe that, first of all, when choosing a heater for a foundation, you need to pay attention to the density, but this is not the right approach. First of all, you need to assess the degree of water absorption of the insulation. After all, the room and walls of a house (both ordinary and wooden) always contain a small amount of moisture, which condenses over time and has a negative effect on the quality of thermal insulation.

In addition, it is important to know that insulation for the foundation will always have good sound insulation, if it is of good enough quality.

When constructing a foundation, the issue of its thermal insulation should be given special attention, especially in regions with a harsh climate and deeply freezing soil.

About 80% of the territory of Russia is located in the zone of heaving soils, which pose a particular danger to foundations.

Heavy soils with seasonal or perennial freezing can increase in volume, which is accompanied by a rise in the soil surface. The rise of the soil surface during the winter can reach 0.35 m (15% of the depth of the freezing soil layer), which in some cases leads to deformation of the structure: freezing with the outer surface of the enclosing structure, the soil is able to lift it due to the tangential forces of frost heaving. When the foundations are laid above the freezing depth of heaving soils or if during the construction process in the winter the foundation slab was not insulated, normal frost heaving forces appear under its sole.

Horizontal thermal insulation of the foundation, with cutting off the frost heaving zone, makes it possible to reduce to zero the risks arising from the rise and thawing of heaving soils.

It has been established that the basement and ground floor foundations account for about 10-20% of all heat losses at home.

Insulation of buried structures allows you to reduce heat losses, protect the foundation structure from freezing, avoid condensation of water vapor on cold walls (associated with insufficient thermal insulation or ventilation in the room), and prevent dampness and mold development. At the same time, in country houses for summer residence, the insulation of the foundation and basement walls does not make sense, except for cases when it is necessary to correct design flaws associated with the consequences of frost heaving of soils.

Thermal insulation requirements are not imposed on unheated basements.... However, it is necessary to insulate the walls at least in the basement area, so that they do not freeze on the border of the overlap between the unheated basement and the heated rooms on the first floor.

In addition, thermal insulation protection is an integral element of the waterproofing system: it protects the waterproofing coating from destruction and temperature aging.

Advantages

• eliminates or significantly reduces the impact on the foundation of the forces of frost heaving;
• reduces heat loss and cuts heating costs;
• provides the required and constant temperature inside the room;
• prevents the formation of condensation on internal surfaces;
• protects waterproofing from mechanical damage;
• helps to extend the durability of the waterproofing.

Insulation for the foundation

Special requirements are imposed on the materials used to insulate the foundation from the outside:

• low water absorption;
• high compressive strength (with low thermal conductivity);
• resistance to aggressive groundwater;
• not susceptible to decay.

Mineral wool is not suitable because of its compressibility when backfilled with soil and high water absorption rates.

Given the low water absorption (< 5%) and high strength ( 0.4-1.6 MPa), foam glass can be used for external vertical and horizontal thermal insulation. True, this option turns out to be several times more expensive.

Expanded polystyrene (styrofoam)

Low short-term compressive strength (

If ordinary foam is used to insulate the foundations from the outside, then it is located under the waterproof layer (: waterproofing of the foundation - foam - waterproofing of the system). Otherwise, a few years after installation, the foam will turn into a shapeless pile of balls. The moisture accumulated in the insulation will increase in volume during freezing and destroy its structure.

In conditions of increased loads and humidity, the most optimal heat-insulating material is.

Due to the properties of the raw materials and the closed-cell structure, which makes it difficult for water to penetrate inside, extruded polystyrene foam has excellent technical characteristics and a long service life, which allows it to be used for basement insulation.

EPPS has practically zero water absorption (no more than 0.4-0.5% by volume for 28 days and for the entire subsequent period of operation), therefore, soil moisture does not accumulate in the thickness of the insulation, does not expand in volume under the influence of temperature changes and does not destroy the structure material throughout its service life (frost resistance over 1000 freeze-thaw cycles).

Due to their strength, extruded polystyrene foam boards increase the service life of the waterproofing coating, protecting it from mechanical damage and providing a positive temperature regime.

Thus, the insulation of the foundation and the basement of the house with extruded polystyrene foam extends the life of the foundation.

Advantages

• stability of thermal insulation properties throughout the entire service life;
• service life not less than 40 years;
• compressive strength ranges from 20 to 50 t / m 2;
• is not a breeding ground for rodents.

Calculation of the thickness of the insulation

The required thickness of the insulation for the basement wall located above ground level is taken equal to the thickness of the insulation for the outer wall and is calculated by the formula:

The required thickness of insulation for a basement wall located below ground level is calculated by the formula:

• δ ut- insulation thickness, m;
• R 0 pref.- reduced resistance to heat transfer of the outer wall, taken depending on the value of the GSOP, m 2 · ° C / W;
• δ - thickness of the bearing part of the wall, m;
• λ - coefficient of thermal conductivity of the material of the bearing part of the wall, W / (m · ° С);
• λ ut- coefficient of thermal conductivity of the insulation, W / (m · ° С).

The required thickness of insulation from extruded polystyrene foam plates in the walls of the basement for all regional and republican centers of the Russian Federation is shown in the table:

The range of EPPS materials includes specially designed thermal insulation boards with milled grooves on the surface. This material, together with geotextile fabric, successfully works as wall drainage, i.e. it performs three functions: insulation of the foundation, protection of waterproofing from mechanical damage and drainage of water from the foundation in the drainage system.

How to insulate the foundation?

When insulating the vertical part of the foundation, polystyrene foam is installed on depth of soil freezing, defined for each region individually. The effectiveness of insulation with a deeper installation is sharply reduced.

The thickness of the insulation in the corner zones should be increased by 1.5 times, at a distance of at least 1.5 m from the corner in both directions.

Insulation of the foundation outside is the most rational, provides a low level of heat loss.

Insulation of the foundation outside

Insulation of the soil along the perimeter of the house under it allows you to reduce the depth of freezing along the walls and under the base of the foundation and to keep the freezing boundary in a layer of non-porous soil - sand, gravel cushion or backfill soil. In this case, extruded polystyrene foam should be laid with a given slope of the blind area ≥ 2% from the house.

Insulation width from extruded polystyrene foam around the perimeter should be at least the depth of seasonal freezing of the soil.

Horizontal insulation thickness must be at least the thickness of the vertical thermal insulation of the foundation.

Insulation of the foundation from the inside

If it is impossible to insulate the foundation from the outside, it is allowed to install thermal insulation from the inside of the room. The installation of thermal insulation from the side of the room is made either by gluing extruded polystyrene foam to the wall surface using solvent-free compounds (for example, on a cement basis), or by fixing the insulation plates mechanically with the subsequent installation of a finishing layer.

In this case, it is mandatory to check the walls of the insulated structure for the possibility of condensation moisture accumulation in it.

In the construction of a wall with extruded polystyrene foam, it shows that such a construction is acceptable.

How to fix polystyrene foam
to waterproofing foundation

The insulation is placed on the leveled outer surface of the walls of the insulated structure after waterproofing on it.

When insulating the foundation from the outside, mechanical fixation of the EPSP boards is not allowed, since in this case the continuous waterproofing coating will be violated!

Extruded polystyrene foam is attached to the waterproofing surface of the walls with glue or by melting the bitumen layer of waterproofing at 5-6 points, followed by tight pressing of the plates.

The bonding of the EPSP should be started from below laying the slabs horizontally in one row. The next row of slabs is installed end-to-end to the already glued bottom row. It is not allowed to re-install the glued boards, as well as to change the position of the insulation after a few minutes after gluing.

Thermal insulation boards must be of the same thickness and fit tightly to each other and to the base. In this case, they should be located with an offset of the joints (in a checkerboard pattern). If the joints between the boards are more than 5 mm, they must be filled with polyurethane foam. Better to use slabs with a stepped edge. They are placed close to the adjacent slabs so that the parts of the L-shaped edges overlap each other. Such installation excludes the appearance of cold bridges. When installing thermal insulation from two or more layers of insulation, the seams between the plates are spaced apart.

The choice of adhesive depends on the waterproofing used. When using waterproofing roll or mastic type on a bitumen basis, a special or is used. When choosing an adhesive, it is necessary to ensure that it does not contain solvents and does not dissolve the expanded polystyrene board during application. For gluing boards to a vertical surface and for sealing joints, it is not recommended to use ordinary polyurethane foam, since due to a large volumetric expansion, "swelling" of the thermal insulation layer can occur, or separation of the boards from the surface due to the occurrence of high stresses between them.

Below ground level, the adhesive layer can be applied in several points around the perimeter and in the center, so that moisture that collects between the surface of the board and the building base can flow down unhindered.

It is forbidden to install insulation on not yet dried bituminous waterproofing for the following reasons:

• during the installation process, the waterproofing elements may "disperse", after which the tightness can no longer be guaranteed;
• Cold bitumen waterproofing products may contain solvent particles that can damage the thermal insulation material. Therefore, when using waterproofing from cold bitumen, it is recommended to let the surface dry for 7 days before installing the extruded polystyrene foam boards.

Insulation of the basement

The plinth should be insulated around the perimeter to reduce thermal bridges and protect the foundation from frost damage and thermal expansion cracks.

The basement of the house is divided into two parts: above and below ground level and is in humid conditions, as it is in constant contact with the ground, it is moistened by rain, melt water and splashing drops.

The facade insulation system based on non-waterproof heat-insulating material, such as expanded polystyrene or mineral wool, should be at a distance of at least 30-40 cm from the upper edge of the soil so as not to be exposed to rain and melt water.

To insulate the basement, it is necessary to use materials that have zero water absorption and do not change their thermal insulation properties in a humid environment. This material is extruded polystyrene foam.

Underground part

In the recessed part of the house, the use of dowels is not required, the backfilled soil presses the glued insulation.

Aboveground part

In the basement area (above the ground level), the extruded polystyrene foam is attached to polymer-cement glue, or any other that provides good adhesion to the base.

If in the underground part of the house it is possible to fix the EPSP only with the help of adhesives, then in the aboveground part of the basement it is necessary to install front dowels at the rate of 4 dowels per slab.

As a heat-insulating layer above ground level, it is possible to use a special grade of extruded polystyrene foam with a milled surface, which ensures better adhesion of adhesives. It is also possible to use standard grades of extruded polystyrene foam with a smooth surface, in this case, to improve adhesion, the surface should be milled using a metal bristle brush or a fine-toothed wood hacksaw.

1. Fastening the insulation (done in the same way as fastening the insulation of the entire facade system to polymer-cement glue)
2. Installation of the first layer of reinforcing glass mesh

   The prepared adhesive solution is applied with a long stainless steel float on the plate vertically in the form of a strip. The thickness of the adhesive should be approx. 3 mm. Apply the mortar from the corner of the house. After applying the glue solution on a segment equal to the length of the prepared mesh, it is leveled with the toothed side of the float until the same thickness of the solution is obtained over the entire surface. On the fresh glue solution, you need to attach the prepared piece of mesh, pressing it in several places to the glue with the edge of the grater or with your fingers. It is necessary to remember about the overlap of the edge of the mesh by 10 cm. With the smooth side of the grater, it is necessary to drown the mesh in the glue solution - first vertically from top to bottom, then diagonally from top to bottom.

3. Dowelling (performed through the first layer of reinforcing fiberglass mesh)
4. Installation of the second layer of reinforcing glass mesh (similar to the first)
5. Plinth finish (possible options):
   • decorative plaster;
   • stone slabs (attached with special glue);
   • ceramic tiles (attached to a special adhesive for decorative tiles).

Insulation of the foundation slab

If it is necessary to insulate the foundation slab, the thermal insulation slabs are placed on the waterproofing. If knitted reinforcement is planned to be used to reinforce a reinforced concrete monolithic foundation slab or load-bearing floor, then it is enough to protect the insulation plates from liquid components of concrete with a polyethylene film with a thickness of 0.15-0.2 mm laid in one layer. If welding is planned for reinforcement work, then on top of the film it is necessary to make a protective screed made of low-grade concrete or cement-sand mortar. Film sheets are laid with an overlap of 10-15 cm on double-sided tape.

Thermal insulation of the home must be started from the foundation, and the best material for this is expanded polystyrene. Warming the foundation with expanded polystyrene is a 100% proven option, + the video will help you master the technology. And although this method is not the cheapest, it is very effective, moreover, it is quite simple to perform.

Insulation characteristics

• 1 Characteristics of insulation
• 2 Preparatory phase
  • 2.1 Calculator for calculating the thickness of the foundation insulation
• 3 Technology of basement insulation
  • 3.1 Step 1. Waterproofing the surface
  • 3.2 Step 2. Fastening of expanded polystyrene
  • 3.3 Step 3. Plastering the foundation
  • 3.4 Step 4. Backfilling the foundation
  • 3.5 Step 5. Making a blind area
  • 3.6 Step 6. Finishing the base
  • 3.7 Video - Insulation of the foundation with expanded polystyrene 100% proven option + video

Expanded polystyrene sheet has a large number of positive properties:

In addition, this material is easy to install and lasts about 40 years if the thermal insulation is made according to all the rules. Styrofoam also has disadvantages:

Do not use organic solvent glue and hot mastic for fixing expanded polystyrene sheets. To protect the insulation from damage, it must be transported and unloaded carefully, not thrown from a height, and after installation, be sure to close it with an external finish - tiles, siding, plaster or at least cement mortar.

Preparatory stage

First you need to calculate how many insulation slabs you need for the foundation. The dimensions of a standard expanded polystyrene plate are 600x1200 mm, thickness is from 20 to 100 mm. For the foundation of a residential building, slabs with a thickness of 50 mm are usually used, laying them in two layers. To find out how many slabs are needed, the total length of the foundation is multiplied by its height and divided by 0.72 - the area of ​​one sheet of expanded polystyrene.

For example, if a foundation with a height of 2 m is insulated in a 10x8 m house, the area of ​​thermal insulation is 72 squares. Dividing it by 0.72, we get the number of sheets - 100 pieces. Since the insulation will be carried out in two layers, it is necessary to buy 200 slabs with a thickness of 50 mm.

This, however, is a very average calculation based on the fact that the thickness of the insulation will be exactly 100 mm. But this value can be more - it all depends on the climatic conditions of the region, and on the material of the foundation, and on the type of insulation.

There is a special system for calculating the thickness, for which you need to know the R index - this is a constant value of the required resistance to heat transfer, set by SNiP for each region. It can be checked with the local department of architecture, or taken from the proposed table:

Calculator for calculating the thickness of the foundation insulation

In order not to bother the reader with calculation formulas, there is a special calculator below that will allow you to quickly and accurately find the required thickness of thermal insulation. The result is rounded up, leading to the standard thickness of the panels of the selected insulation:

Calculation of the minimum insulation thickness for the outer walls of the foundation

Enter the sequentially requested data and click the "Calculate" button

Enter the tabular value of the heat transfer resistance value for your region (decimal fraction - through a dot)

Select the type of insulation

polystyrene foam extruded polyurethane foam sprayed polyurethane foam panels

Specify the thickness of the foundation tape

200 mm 250 mm 300 mm 350 mm 400 mm 450 mm 500 mm

In addition to expanded polystyrene, you will need:

When all the materials are prepared, a trench is dug around the perimeter of the foundation. You need to dig to the level of freezing, that is, to a depth of 1.5-2 m. To make it convenient to work in a trench, its width should be 0.8-1 m. The walls of the base must be thoroughly cleaned of earth, bumps and cracks must be repaired with mortar.

Foundation insulation technology

The process of warming consists of the following stages: waterproofing the surface, fixing expanded polystyrene, external finishing of the foundation. After excavating the earth, you need to wait until the base dries well, and only then proceed to isolate the walls.

Step 1. Waterproofing the surface

On dry, even walls of the foundation, a coating waterproofing is applied with a layer of 4 mm. The mastic should be used without organic solvents, preferably polymer or water based. The mixture is applied with a roller, trying to fill the pores and small gaps in the concrete well. You can use only roofing material for waterproofing or combine both materials: apply roofing material over the mastic and glue the joints with the same mixture.

The moisture protection layer must completely cover the entire surface of the base and plinth and have no gaps.

Step 2. Fixing polystyrene foam

When the mastic dries, you can proceed to the main stage. They take the first sheet of insulation and apply glue from the back either in longitudinal stripes or pointwise, the main thing is that the glue is in the center of the sheet and along the edges. 1-2 minutes after application, the sheet is applied to the foundation, its position is checked and pressed firmly. The slabs are attached to the foundation only with glue so as not to violate the integrity of the base, and on the plinth the slabs are additionally strengthened with dowels-fungi.

Fixing the dowel-g8bka

The next sheet must be fastened from the side close to the first so that the joints are as tight as possible. Be sure to control the level of the location of each fragment - this will exclude the formation of distortions. Laying is carried out from the bottom up, while it is recommended to shift the vertical seams by half a sheet to the side. When the first layer is fully fixed, proceed to the second. Everything is repeated in the same way, only the joints of the upper layer should not coincide with the joints of the lower one - the plates must be laid with an offset. In conclusion, the layer of thermal insulation is carefully examined and, if cracks in the seams are detected, they are blown out with foam.

When insulating the basement, the sheets are laid immediately on the glue, and the dowels are used after 2-3 days, when the glue is already dry. Each slab is fixed at the corners and in the center; for economy, fasteners can be placed on the seams.

Step 3. Plastering the foundation

To protect the expanded polystyrene boards, another layer is needed, for example, plaster. The basement can be covered with siding or veneered with porcelain stoneware. First, a fiberglass mesh is fixed on top of the slabs using dowels with large caps. At the joints, you need to lay the reinforcing material with an overlap of 10 cm. It is recommended to stretch the mesh well so that folds do not form, which will lead to cracking of the plaster layer.

Surface leveling is performed with cement-sand mortar or acrylic glue. The first method is much cheaper, and therefore it is used more often. The solution is made thick enough and applied with a wide spatula, firmly pressing the mixture into the mesh cells. The plaster layer should be of the same thickness over the entire area. The foundation is plastered to the level of the backfill, and the basement is finished a little later.

Step 4. Backfilling of the foundation

It is impossible to fill up the trench until the plaster is dry. First, a 10-centimeter layer of sand is poured onto the bottom, leveled and tamped, then a gravel pad 20 cm thick is arranged. You can replace gravel with expanded clay mixed with sand - this will increase the thermal insulation properties of the base. Further, the trench is covered with soil with compulsory compaction every 25-30 cm. When 40 cm remains to the top of the trench, a blind area should be made around the entire perimeter of the foundation.

Step 5. Making a blind area

On top of the soil, a layer of gravel about 10 cm is poured over the width of the trench, tamped tightly.

We lay polystyrene foam, reinforcing mesh, install formwork and expansion joints

Roofing material is spread over the gravel; at the joints, the material is overlapped by 12-15 cm and coated with bitumen. The next layer is expanded polystyrene: the plates are tightly stacked in one row along the perimeter of the house. Further, around the slabs, formwork is mounted from boards with a height of about 10 cm. For strength, a metal lattice with small cells is placed in the formwork. A thick cement mortar is prepared and poured so that a slight slope forms from the wall. The sloping surface facilitates the outflow of melt and rainwater.

Step 6. Finishing the base

As soon as the blind area is dry, you can begin the exterior finishing of the basement. Since this plot is high above the ground and is highly visible, the finishing must be very neat and attractive. The easiest way is to plaster the surface and cover it with facade paint. Before applying the plaster on the expanded polystyrene plates, a reinforcing mesh is fixed. If desired, you can give the surface a volumetric texture, or vice versa, make the wall absolutely smooth.

Most often, the basement is finished with decorative stone or tiles. To do this, the plastered surface is primed, dried, and then the finishing material is attached to the glue.

It is very important to seal the seams between the fragments so that moisture does not penetrate through them to the insulation.

On this, the thermal insulation of the foundation is considered completed. If all the conditions are met, it will not take a very long time to change the insulation.

Video - Insulation of the foundation with expanded polystyrene 100% proven option + video

The correct calculation of thermal insulation will increase the comfort of the house and reduce heating costs. During construction, you cannot do without insulation, whose thickness determined by the climatic conditions of the region and the materials used. For insulation, polystyrene, polystyrene foam, mineral wool or ecowool are used, as well as plaster and other finishing materials.

To calculate how thick the insulation should be, you need to know the value of the minimum thermal resistance... It depends on the characteristics of the climate. When calculating it, the duration of the heating period and the difference between internal and external (average for the same time) temperatures are taken into account. So, for Moscow, the resistance to heat transfer for the outer walls of a residential building should be at least 3.28, in Sochi, 1.79 is enough, and in Yakutsk, 5.28 is required.

The thermal resistance of a wall is defined as the sum of the resistance of all structural layers, bearing and insulating. That's why the thickness of the insulation depends on the material from which the wall is made... For brick and concrete walls, more insulation is required, for wood and foam blocks less. Pay attention to the thickness of the material chosen for the supporting structures, and what is its thermal conductivity. The thinner the supporting structures, the greater the thickness of the insulation should be.

If a thick insulation is required, it is better to insulate the house from the outside. This will provide savings in interior space. In addition, external insulation avoids the accumulation of moisture inside the room.

Thermal conductivity

The ability of a material to transmit heat is determined by its thermal conductivity. Wood, brick, concrete, foam blocks conduct heat in different ways. Increased air humidity increases thermal conductivity. The value inverse to thermal conductivity is called thermal resistance. To calculate it, the value of thermal conductivity in a dry state is used, which is indicated in the passport of the material used. You can also find it in the tables.

However, one has to take into account that in corners, joints of load-bearing structures and other special structural elements, thermal conductivity is higher than on a flat surface of walls. Cold bridges may arise through which heat will escape from the house. The walls in these areas will sweat. To prevent this, the value of the thermal resistance in such places is increased by about a quarter compared to the minimum allowable.

Calculation example

It is not difficult to calculate the thickness of the thermal insulation using a simple calculator. To do this, first calculate the resistance to heat transfer for the supporting structure. The thickness of the structure is divided by the thermal conductivity of the material used. For example, foam concrete with a density of 300 has a thermal conductivity coefficient of 0.29. With a block thickness of 0.3 meters, the value of the thermal resistance:

The calculated value is subtracted from the minimum value. For Moscow conditions, the insulating layers must have a resistance not less than:

Then, multiplying the thermal conductivity of the insulation by the required thermal resistance, we obtain the required layer thickness. For example, for mineral wool with a thermal conductivity coefficient of 0.045, the thickness should not be less than:

0.045 * 2.25 = 0.1 m

In addition to thermal resistance, the location of the dew point is taken into account. The dew point is the place in the wall where the temperature can drop so much that condensation - dew will fall out. If this place is on the inner surface of the wall, it fogs up and a putrefactive process can begin. The colder it is outside, the closer the dew point is to the room. The warmer and more humid the room, the higher the temperature at the dew point.

The thickness of the insulation in the frame house

As a heater for a frame house, mineral wool or ecowool is most often chosen.

The required thickness is determined using the same formulas as for traditional construction. Additional layers of a multi-layer wall give approximately 10% of its value. The wall thickness of a frame house is less than with traditional technology, and the dew point can be closer to the inner surface. That's why it is not worth saving too much on the thickness of the insulation.

How to calculate the thickness of roof and attic insulation

The formulas for calculating the resistance for roofs use the same, but the minimum thermal resistance in this case is slightly higher. Unheated attics are covered with bulk insulation. There are no restrictions on thickness, so it is recommended to increase it by 1.5 times relative to the calculated one. In the attic, materials with low thermal conductivity are used for roof insulation.

How to calculate the thickness of floor insulation

Although the greatest heat loss occurs through the walls and roof, it is equally important to correctly calculate the floor insulation. If the basement and foundation are not insulated, it is considered that the temperature in the subfloor is equal to the outside temperature, and the thickness of the insulation is calculated in the same way as for the outer walls. If some insulation of the basement is done, its resistance is subtracted from the value of the minimum required thermal resistance for the construction region.

Calculation of the thickness of the foam

The popularity of foam is determined by its cheapness, low thermal conductivity, light weight and moisture resistance. Styrofoam almost does not allow steam to pass through, so it cannot be used for internal insulation... It is located outside or in the middle of the wall.

Thermal conductivity of foam, like other materials, depends on density... For example, with a density of 20 kg / m3, the thermal conductivity coefficient is about 0.035. Therefore, a foam thickness of 0.05 m will provide a thermal resistance of 1.5.