Against the backdrop of constantly rising energy prices, people are increasingly beginning to think about high-quality insulation housing. Insulating a home with expanded polystyrene has long become the norm. This technology multifaceted and consists of several stages. One of the most important areas is the thermal insulation of the foundation, and in this article I will tell you why you need to insulate the foundation at all and will dwell in detail on how to independently insulate your foundation with extruded polystyrene foam.
General information about materials or the role of insulation in the arrangement of the foundation
First, let's understand the terms. Expanded polystyrene is commonly called a lightweight cellular material created on the basis of styrene.
Now there are 2 types of this popular material most widely represented on the market:
- Well-known polystyrene foam in technical language is called cellular polystyrene foam. This material was developed in the first half of the last century and is now one of the most popular insulation materials;
- Extruded polystyrene foam has the same base, but is produced using a different technology. Its characteristics are an order of magnitude higher, but the price of its extruded counterpart is at least 2 to 3 times higher than the cost of good polystyrene foam.
Why extruded polystyrene foam
Those owners who were already interested in prices probably noticed that insulating a house with extruded polystyrene foam is a rather expensive idea. It is much cheaper to sheathe a house simple polystyrene foam, for example, PSB-S25, which, by the way, is done in most cases.
But here any normal person has a reasonable question: if the whole house can be insulated with inexpensive polystyrene foam, then why do you need to pay more for extruded polystyrene foam for the foundation? At one time I also thought about this, and it turned out that there were several reasons.
Let's start with the fact that polystyrene foam is not called a cellular material for nothing; everyone has noticed that the balls can be easily crushed with your own hands, the connection between them is loose.
Consequently, where there are gaps, water will definitely penetrate and as soon as frost hits, the slabs will slowly begin to crumble, which means that they need to be well protected from above, while extruded polystyrene foam is a dense, monolithic material, the structure of which, in principle, contains moisture cannot penetrate.
If we take the tabular data, the water permeability of polystyrene foam is 3–4%, and expanded polystyrene has a maximum rate of 0.4%. And then this 0.4% is given for water permeability in the cut areas of the sheets, that is, where the integrity of the cells is compromised.
At one time, extruded lightweight polystyrene foam was developed for the needs of the navy; life jackets and other similar products were supposed to be made from it. But it soon became clear that these slabs have phenomenal strength and are much more in demand in the construction industry.
Nowadays, not a single decent highway or airfield runway can do without insulation of the road surface. And here exclusively extruded polystyrene foam is used.
Extruded plates can withstand pressure up to several tens of tons per square meter. By the way, the foam begins to crumple already at a pressure exceeding 100 - 200 kg. And this, as you understand, is very small when planting it in the ground.
Now let's move on to more banal things. The owners of private houses know very well that polystyrene foam is a favorite habitat for mice; these creatures feel warm and cozy there. Insulating the house with extruded polystyrene foam completely eliminates this problem.
The maximum service life of foam plastic insulation according to standards does not exceed 25 years. And the warranty for extruded polystyrene foam only starts at 40 years.
And finally, if we compare materials in terms of thermal conductivity, then polystyrene foam is inferior to its younger relative by about a third. That is, where you need a foam thickness of 100 mm, you can get by with 70 mm polystyrene foam.
I know of only one way to use thick foam to insulate a foundation below ground level. This is when brickwork is installed on top of the foam to protect it. But the price of this option is several times higher than the most expensive extruded polystyrene foam.
Is it necessary to insulate the foundation?
Even 20 - 30 years ago it was believed that monolithic reinforced concrete foundations should not be protected, much less insulated. Allegedly with such heavy durable structures and nothing will happen.
Now the concept has changed, and for the following reasons:
- Indeed, a monolith laid below the freezing level of the soil is quite capable of withstanding soil movements during frost heaving. But no matter how strong the concrete is, it will sooner or later begin to deteriorate due to constant freezing. External thermal insulation foundation with expanded polystyrene completely eliminates the problem of freezing of the monolith and increases its service life several times;
- For shallowly buried structures, frost heaving is the worst enemy. There have been cases when such tapes not only cracked, but were completely torn out. It turned out that if you “wrap” a shallow concrete foundation in a jacket made of extruded polystyrene foam, then it is no longer afraid of soil movements. Please note that polystyrene foam is not able to withstand such pressure; it will simply be crushed;
- A modern capital house is unthinkable without good basement, and sometimes even an entire technical floor with a garage, laundry and other premises. So, insulating the foundation with polystyrene foam automatically relieves the owners of constant condensation on the walls of the basement rooms. You get a cool yet dry basement;
Such a newfangled technology as the “Swedish stove”, which is designed for the construction of energy-saving houses in the north and on unstable soils, was initially developed using extruded polystyrene foam. It cannot be realized with other insulation.
- But almost the most important reason, proving the need to insulate the foundation, are serious losses of heat, and therefore money in cold period time. Which, by the way, is on larger territory our great power lasts at least six months. So, if we look at the hard numbers, it turns out that in a house with a conventional strip foundation, heat loss from the foundation is about 20%, and in cottages with a recessed basement, the losses reach 25%. Agree, taking into account current fuel prices, the amount accumulates in six months is substantial.
How to insulate a foundation with extruded polystyrene foam
So, we found out that insulating the foundation with polystyrene foam is not a newfangled trend, but an urgent necessity, and it cannot be replaced with anything else. Now let's look at the practical side of the issue and, like all normal builders, let's start with calculations.
Calculations for insulating the foundation
Naturally, in order to make accurate engineering calculations you need, at a minimum, to have a technical education. Now there is such a useful thing on the Internet as an electronic calculator.
But if both of these options are not available to you for some reason, then you can use a simpler formula. An experienced construction engineer once suggested it to me.
H = (R – h/K1)K2
- H – the required thickness of extruded polystyrene foam for the foundation;
- R – heat transfer resistance. If we omit the exact table values, then on average for Russia we take about 3.5 m²K/W;
- h – thickness of the foundation tape;
- K1 – thermal conductivity coefficient of the material from which the foundation is made. For concrete it ranges from 1.3 – 1.7 W/mK, on average you can take 1.5 W/mK;
- K2 is the thermal conductivity coefficient of the insulation you have chosen. The instructions on the packaging will help you here; this information will definitely be there.
Calculation required quantity extruded polystyrene foam slabs are even simpler: calculate the quadrature of the foundation, that is, multiply the length by the height, divide the final figure by the quadrature of the sheet, then round up and add 10 - 15% for trimming and arranging corners.
With the number of sheets, everything seems to be clear, but regarding the thickness of the sheets, I usually advise that if you have the means, it is better to take 100 mm. If you don’t have enough money, then 50 mm. In general, it is believed that for central Russia 50 mm is enough and the further north the area, the thicker the insulation, the maximum is 150 mm.
A few words about the instrument
The number of tools depends on the technology you choose. What you need is a hammer drill, several metal spatulas with a blade width from 10 to 40 cm and a knife for cutting polystyrene foam boards.
To install good roll waterproofing, you will need a gas torch; in extreme cases, you can get by with a blowtorch, but it will work worse. Naturally, tools such as a tape measure, level, hammer, etc. should be in the kit of any self-respecting owner.
External foundation insulation
Insulation of the foundation from the outside is deservedly considered the most effective way arrangement load-bearing structures. IN in this case the concrete monolith itself remains in the positive sector. The dew point (the place where the temperature is 0ºC) will be located in the insulation, in our case in extruded polystyrene foam.
In the vast majority of cases, the foundation is insulated during the construction stage of the building. Although no one is stopping you from insulating the capital foundation of an old house, you will only have to dig it up to do this.
The technology involves laying insulation just below the freezing point of the soil. Of course, if you don’t mind the money, then you can completely cover the base with slabs of extruded polystyrene foam, but there is little point in this, because below the freezing point of the soil, waterproofing alone is enough.
Theoretically, such expanded polystyrene is already waterproofing in itself, but there is a high probability of movement in the soil and so that after a couple of years moisture, and with it the cold, does not reach the foundation, it is necessary to apply a starting waterproofing layer to the monolith.
In order for the waterproofing to take place as expected, the concrete base should be well prepared. At the first stage, you will need to clean the monolith from any remaining soil. Of course, if the foundation has just been poured, then there is nothing to clean there. This procedure is only needed for old foundations that were already in the ground.
Now to increase adhesion you will need to coat the monolith with a primer. There are special bitumen-based primers for this, but if you don’t want to spend money on them, then mix bitumen with gasoline or diesel fuel in a 1:1 ratio and coat your foundation. The composition is not expensive, tested and dries within an hour.
I do not recommend saving on waterproofing for the foundation. I, like most experts, believe that the highest quality results are obtained by rolled waterproofing, which is installed with heating. Well established in this sector roll materials from the TechnoNIKOL brand.
To fix such rolls you will need a gas torch or blowtorch(working worse with a lamp). The tapes are mounted vertically. First, roll out a large roll, cut required quantity ribbons and roll them into small rolls.
Then you heat the edge of each small roll and attach it to the foundation from below. Then gradually roll it out from the bottom up and at the same time heat the canvas.
The sector heated by the burner is slightly pressed against the monolith, there is no need to be zealous, such waterproofing sticks well after heating. The tapes are laid with a slight overlap.
But this is not the only option. A coating made of liquid rubber gives a fairly high-quality result. Here it is better, of course, to call professionals with special equipment and they will cover your entire foundation with rubber in a day. Although, if you don’t mind the effort and time, you can buy liquid rubber in the form of a coating and apply it to the monolith with your own hands using a spatula.
After the waterproofing layer has completely hardened, you can begin to fix extruded polystyrene foam on it. This type of insulation is produced by several leading world brands; in our country, Penoplex is usually used. Plates from this manufacturer are equipped with L-shaped grooves around the perimeter, which provides a tighter and higher-quality connection.
Extruded polystyrene foam below ground level, that is, underground to the foundation, more precisely to the waterproofing, can only be glued. No dowels or other through fixation options are used here. In the ground, the integrity of the slabs and waterproofing layer must not be compromised under any circumstances.
For gluing to the waterproofing layer, it is better to use polymer-based glue. You can do it even simpler: if you heat the waterproofing with a torch at several points and apply a slab to it, the slab will stick perfectly.
The only thing that is strictly forbidden to use are adhesives made with organic solvents, such as gasoline, toluene, acetone and others. The fact is that organic solvents corrode both polystyrene foam and extruded polystyrene foam.
The slabs are glued from any angle, similar to brickwork, that is, with a shift between the rows. The corner is considered the weakest point in the foundation, so it is recommended to insulate it in 2 layers, with a 1m overlap on the wall planes.
For those owners who like to do everything with a solid margin of safety, there is a two-layer technology for installing insulation. It consists in gluing the same layer on top of the first layer of 50 mm thick slabs.
Only the joints between the slabs of the first and second layers should not coincide. This technology is also good because it does not require additional reinforcement of the corners.
When the insulation is finished, you can fill the trench, but there is small nuance: extruded polystyrene foam can withstand serious pressure along the plane, but large point loads can damage the insulation.
To prevent random stones or any other hard objects that sometimes appear in the ground from pushing through your polystyrene foam for the foundation, sand should be the first layer about 20 cm thick.
Therefore, the trench must be dug carefully, at the same time throwing a layer of sand towards the foundation wall and adding regular soil further. Plus, this layer cake needs to be compacted every half meter.
Warm blind area and drainage as additional protection for the foundation
As you know, prevention of a problem has always been an equally important part of its solution. Serious freezing of the soil in the area of the foundation can be, if not completely eliminated, then significantly reduced by insulating the blind area around the perimeter of the house with extruded polystyrene foam.
If you strictly follow the technology, then the size of the blind area should be equal to the depth of soil freezing in a given region. But I can say from myself that this rule should be observed only on heaving soils. In the case where the house stands on stable soils, a blind area of about a meter in size is sufficient.
It’s not difficult to equip it with your own hands. To insulate the blind area, slabs 50 mm thick are sufficient. Initially, soil is selected for the structure to a depth of about 200 mm. The bottom of the pit is well compacted and covered with geotextile or roofing felt.
A sand cushion about 50 mm thick is poured onto it and also compacted. A layer of extruded polystyrene foam is laid on this pillow with a slope of 20 - 30 mm per 1 meter.
A reinforcing frame will need to be tied on top of the insulation. Reinforcement that is too thick does not require sufficient steel wire with a diameter of 6 mm (rod rod). Although, in order not to bother with the knitting of the reinforcement frame, I lay the usual one in 2 layers with a gap of 30 mm steel mesh chain-link In the area of the blind area the load is negligible and great strength not required there.
After this, again ensuring a slope of 20 - 30 mm, the whole thing is filled with concrete. The thickness of the concrete layer is around 100 mm. The slope is needed so that water flows freely from the blind area.
But all this is good if the groundwater runs much lower than your foundation. In cases where there is a high probability of flooding of the building, in order to drain groundwater from the monolith and insulation, you will have to install drainage.
If you have completed the installation of insulation, then the arrangement drainage system You shouldn't have any problems. In this case, a small layer of gravel is poured onto the bottom of the trench around the house and a plastic drainage pipe with a cross-section of 100 mm or more (a pipe with many holes) is laid on it.
Keep in mind that the drainage pipework must be laid below the freezing level of the soil, pass no closer than 300 mm from the border of the insulation and be installed with a slope towards the central well, the slope is 10 - 20 mm per 1 linear meter.
Plus, at all pipe turns you need to make intermediate inspection wells. The central well is needed to collect water and naturally it is made larger and deeper. The water is either pumped out or taken to another place.
IN standard version We have a layer of sand behind the insulation and then soil, and to arrange drainage instead of soil on top drainage pipe a layer of crushed stone is poured, the thickness of such a layer ranges from half a meter to a meter.
The general structure of the system is shown in the diagram. The foundation and the blind area bordering it are insulated with extruded polystyrene foam. And to prevent water from breaking through to the insulation, a drainage system is installed.
Insulation of the foundation from the inside
I’ll tell you honestly, insulating the foundation with polystyrene foam from the inside is not the best option. In this case, the concrete monolith itself has frozen and will continue to freeze, but you get a dry basement and a relatively warm floor.
The technology is extremely simple. The insulation boards are glued to the wall in the same way as we glued them on the outside for waterproofing. To install extruded polystyrene foam on bare concrete, I use mortar“Ceresit CT83”, by the way, it was developed precisely for these purposes.
But glue alone will not be enough here; the insulation will need to be additionally secured and plastered. When the insulation is installed, the same construction adhesive with a thickness of 2–3 mm is applied to it.
While the glue is still wet, a fiberglass reinforcing mesh is embedded into it using a spatula, after which holes in the concrete are drilled through the insulation and plastic umbrella dowels are driven into them.
Next you will need to wait for it all to dry, lightly sand the surface with coarse sandpaper and apply a layer finishing putty on a cement base. That's basically it. Remember that from the inside, in the basement, it is enough to insulate the outer walls and ceiling.
Conclusion
Thermal insulation of the foundation with polystyrene foam is the most effective way to get rid of cold floors and protect the concrete monolith from destruction. The photos and videos in this article show some practical aspects of the arrangement process. If you have any questions, write them in the comments and we’ll talk.
The foundation is the basis on which not only the durability and strength of the building depends, but also its thermal insulation qualities. Without additional protection of this part of the building, about 20% of the heat will escape from the room. To prevent heat loss, you should use special materials - insulation.
Expanded polystyrene is one of the most common types of thermal insulation, used in almost any part of the building. It is used to protect foundations, facades and roofs, as well as to create custom blocks that allow the restoration of almost any damaged decorative element on ancient buildings.
Expanded polystyrene is the most popular material in modern construction. The raw material for its production is the same as for polystyrene foam - polystyrene, a product of styrene polymerization. But the creation technology is completely different. When making polystyrene foam, this polymer is placed in a block mold and treated with water steam. Its granules increase in size due to micropores and sinter with each other. But due to the formation of voids, this processing option greatly reduces the strength of the material.
Expanded polystyrene, depending on the production method, can be foamed (EPS) or extruded (XPS). In the first option, polystyrene granules are filled with pentane and heated under the influence of steam, resulting in an increase in their size tens of times. The balls are filled with air, becoming elastic, and then stick together.
The second type of material is produced using extrusion - by pressing molten polystyrene through a molding hole. The structure of the polymer changes: strong molecular bonds are formed, which increases density, moisture resistance and thermal insulation qualities. This insulation is lightweight and frost-resistant, but is fire hazardous, which is why flame retardants are added to the material - substances that accelerate attenuation.
Extruded polystyrene foam, due to its solid structure consisting of closed granules filled with gas molecules, is more resistant to impacts external environment and liquids. But the cost of this thermal insulation is 3 times higher than that of conventional foam plastic.
When producing polystyrene foam boards, a large block is first produced, which is then cut into standard sheets. They can be of different thickness.
Advantages and disadvantages of the material
The advantages of expanded polystyrene include:
- low thermal conductivity;
- soundproofing qualities;
- moisture resistance;
- light weight;
- ease of processing (it can be easily cut with a saw or knife);
- ease of fastening;
- excellent adhesion to other materials;
- frost resistance (withstands up to -50°C);
- safety during operation (expanded polystyrene does not smell, does not generate dust and does not emit toxic fumes);
- preservation of material properties for a long time (about 50 years);
- no shrinkage;
- biological resistance (does not mold).
Disadvantages of the material:
- flammability (special additives make it self-extinguishing);
- may release harmful substances when ignited;
- low strength;
- hygroscopicity;
- inelasticity;
- instability to ultraviolet radiation.
Styrofoam brands
In accordance with the requirements of GOST 15588-86, expanded polystyrene boards (PSB) are divided into two types, depending on the presence of fire retardant in their composition:
- PSB-S – self-extinguishing,
- PSB - ordinary.
GOST 15588-86. Polystyrene foam boards. Specifications. File for download.
According to the maximum density value of the material, PSB is further divided into grades: 15, 25, 35 and 50. The higher this parameter, the harder the board and the greater the load it can withstand. For example, PSB-S-15 is used indoors, PSB-S-50 is suitable for industrial structures, including road construction. For foundation insulation, the PSB-S 35 brand is most often used.
Calculation of the optimal thickness and amount of material
If you have decided to insulate the foundation of your house with polystyrene foam, you first need to find out optimal thickness material and its required quantity.
The first step is to determine the purpose of the work:
- reduction of heat loss in the room;
- basement insulation;
- converting a basement into a living room.
The required thickness also depends on:
- climate;
- operation and purpose of the building;
- measures to protect against moisture condensation;
- energy saving.
The most important characteristic for foundation insulation is its thermal conductivity. The lower this value, the better the heat is retained. Thermal conductivity can be defined as the amount of thermal energy that passes through a material with an area of 1 m² if the surface temperature difference is 1 °C. This value is measured in W/m²*°C. To calculate the required insulation thickness, you need to know one more value - heat transfer resistance. It is measured in m²*°C/W. To calculate it, you can use the following formula: R=d/k, where d is the thickness of the wall, K is the thermal conductivity coefficient, and R is the required thickness of polystyrene foam.
Table. Calculation of thermal insulation thickness.
| Thermal insulation thickness, mm | Heat transfer resistance, m2*°C/W | Thermal conductivity coefficient, W/m2*°C |
|---|---|---|
| 40 | 1 | 0,83 |
| 50 | 1,25 | 0,68 |
| 60 | 1,50 | 0,58 |
| 70 | 1,75 | 0,51 |
| 80 | 2,00 | 0,45 |
| 100 | 2,50 | 0,37 |
| 120 | 3,00 | 0,31 |
| 130 | 3,25 | 0,39 |
| 140 | 3,50 | 0,27 |
Important! Correct calculation of thermal conductivity will help improve operating efficiency heating system and will save a lot of money. There is no need to immediately buy too thick slabs, as their cost is higher. It is more profitable to calculate the optimal option in advance.
The required amount of polystyrene foam can be calculated by multiplying the height by the perimeter of the house and dividing the resulting value by its area. The final result will help you find out how much polystyrene foam you need in sheets. To work, you will also need glue, the consumption of which depends on the manufacturer and is indicated on the packaging.
Penoplex prices
Penoplex
Vertical installation method
The vertical option is suitable for both houses that are still under construction and those that are in operation. It is best to use it for a house under construction. This method consists of the following steps.
Step 1. The surface must first be dug up, cleaned of soil, debris, including construction debris, mold, dust and grease stains.
Step 2. It is then leveled using cement mortar and perform coating waterproofing without using solvent-based mastic. This is necessary in order to avoid the foundation getting wet from groundwater.
Prices for bitumen mastic
Bitumen mastic
Step 3. Contact glue diluted and, while it matures, mark the lower limit of laying on work surface. The slabs can be buried a little.
Step 4. The glue is applied in strips around the perimeter and in the center, after a minute the slab must be pressed to the base and held in this position for several seconds. If necessary, align it and attach the next one, inserting it into the groove. It is better to use a level to prevent distortions. If a second layer is needed, it is positioned so as to overlap the seams of the previous one. This arrangement of the plates contributes to better insulation.
Step 5. The part of the foundation that will remain underground is no longer strengthened in any way - then it will still be pressed down by the soil.
Step 6. After the glue has dried, the slabs are attached to the remaining surface using dowel nails. They are driven into the surface by 4 cm.
Video - Procedure for insulating the foundation with polystyrene foam
Horizontal installation method
Horizontal insulation is used for slab foundations and belt type, for which polystyrene foam up to 10 cm thick is taken.
Step 1. First, the site is cleared of soil, leveling the bottom; the last few centimeters are removed manually.
Step 2. The base is covered with sand, which needs to be compacted.
Step 3. Temporary formwork is performed, which is filled with a layer of concrete without reinforcement.
Step 4. Then, when it hardens, laying the slabs begins.
Step 5. A thick film is placed on top as waterproofing, which is glued with tape.
Step 6. Formwork is made, then reinforcement is made and the foundation is poured.
Step 7 When the formwork hardens, it is removed and additional thermal insulation of the side walls is performed.
Video - Monolithic slab foundation. Insulation and waterproofing
Video - Monolithic slab - technology
Thermal insulation of the blind area
Insulation of the soil around the building is used to protect it (the soil) from heaving and reduce the depth at which the foundation is laid. Expanded polystyrene prevents deformation. This increases the reliability and durability of the base.
Thermal insulation of the surface begins with vertical laying, after which the sand is poured back 15 cm below the ground level. The formwork is carried out at a distance of about a meter from the wall, the bottom is leveled and compacted. After this, the slabs and waterproofing film are laid and the concrete is poured. It needs to be aligned so that it is slight slope to the outside. If the concrete has hardened, the formwork is removed and the blind area is finished with stone or paving slabs.
Protection of slabs from external influences
Finishing the base is necessary not only for decorative look, but also to protect polystyrene foam from external influences. It is very important to protect the insulation from ultraviolet rays and damage from small animals.
In order to maintain the integrity of the insulation, you need to cover it with reinforcing mesh or panels made of wood shavings. The mesh is also attached using a dowel. Apply on top cement plaster. Additional waterproofing components can be added to the solution, which will help avoid the material getting wet. When the surface is dry, it can be painted or any cladding material can be attached.
Prices for facing materials
Video - Attaching reinforcement mesh to polystyrene foam
If the building is located on wet ground or the groundwater level is very high - when insulating the foundation, drainage is required (this can be a perforated pipe laid on a bed of crushed stone). It is made around the perimeter and taken to a specially designated place.
Insulating the foundation with polystyrene foam boards eliminates freezing, helps eliminate temperature changes on several sides and prevents the formation of condensation. This reduces the humidity in the basement and basement, improves the microclimate and saves money on heating the room. Positive influence thermal insulation also helps to increase the service life of the building. Expanded polystyrene can be used not only outside, but also indoors, it is easy to work with, and its long service life allows it to remain the most popular thermal insulation material on the market.
Video - Insulating the foundation from the outside with polystyrene foam
When constructing a foundation, the issue of its thermal insulation should be given Special attention, especially in regions with harsh climates and deeply frozen soil.
About 80% of the territory of Russia is located in the zone of heaving soils, which pose a particular danger to foundations.
Heaving soils with seasonal or long-term freezing are capable of increasing 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 layer of soil), 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 laying foundations above the freezing depth of heaving soils or if the foundation slab was not insulated during the construction process in winter, normal frost heaving forces arise under its base.
Horizontal thermal insulation of the foundation, cutting off the zone of frost heaving, allows you to reduce to zero the risks arising from the rise and thawing of heaving soils.
It has been established that the foundations of basements and ground floors account for about 10-20% of all heat loss in a house.
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 the appearance of dampness and mold development. At the same time, in country houses for summer living, insulating foundation and basement walls does not make sense, except in cases where it is necessary to correct design defects associated with the consequences of frost heaving of soils.
There are no thermal insulation requirements for unheated basements. However, it is necessary to insulate the walls at least in the basement area so that they do not freeze at the boundary of the ceiling between the unheated basement and the heated rooms of the first floor.
In addition, thermal insulation protection is constituent element waterproofing system: protects the waterproofing coating from destruction and temperature aging.
Advantages
- eliminates or significantly reduces the impact of frost heaving forces on the foundation;
- reduces heat loss and reduces heating costs;
- provides the required and constant temperature indoors over time;
- prevents condensation from forming on internal surfaces;
- protects waterproofing from mechanical damage;
- helps extend the durability of waterproofing.
Insulation for the foundation
Materials used to insulate the foundation from the outside are subject to special requirements:
- low water absorption;
- high compressive strength (with low thermal conductivity);
- resistance to aggressive groundwater;
- resistance to rotting.
Mineral wool is not suitable due to its compressibility when backfilling with soil and high water absorption rates.
Considering 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 (foam)
Low short-term compressive strength (
If you use regular foam plastic to insulate foundations from the outside, then it is located under a waterproof layer (: foundation waterproofing - foam plastic - system waterproofing). Otherwise, a few years after installation, the foam will turn into a shapeless pile of balls. Moisture accumulated in the insulation will increase in volume when freezing and destroy its structure.
Under conditions of increased loads and humidity, the most optimal thermal insulation 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 foundation 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 ground 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 of more than 1000 freeze-thaw cycles).
Due to the strength of the slab extruded polystyrene foam increase the service life of the waterproofing coating, protecting it from mechanical damage and providing positive temperature regime.
Thus, insulating the foundation and base of the house with extruded polystyrene foam extends the service life of the foundation.
Advantages
- stability of thermal insulation properties throughout the entire service life;
- service life of at least 40 years;
- compressive strength ranges from 20 to 50 t/m2;
- is not a breeding ground for rodents.
Calculation of insulation thickness
The required insulation thickness for a basement wall located above ground level is assumed to be equal to the insulation thickness for the outer wall and is calculated using the formula:
The required insulation thickness 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 GSOP, m 2 °C/W;
- δ - thickness of the load-bearing part of the wall, m;
- λ - coefficient of thermal conductivity of the material of the load-bearing part of the wall, W/(m °C);
- λ ut- thermal conductivity coefficient of insulation, W/(m °C).
The required thickness of insulation from extruded polystyrene foam boards in basement walls for all regional and republican centers of the Russian Federation is given in the table:
The line of EPS 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: insulating the foundation, protecting the waterproofing from mechanical damage and draining 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 soil freezing depth, determined for each region individually. Insulation efficiency at more deep installation decreases sharply.
The thickness of insulation in corner areas 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 from the outside is the most rational, provides a low level of heat loss.
Insulation of the foundation from the outside
Insulating the soil around the perimeter of the house allows you to reduce the depth of freezing along the walls and under the base of the foundation and maintain the freezing limit in a layer of non-heaving soil - a sand, gravel bed or backfill soil. In this case, extruded polystyrene foam must be laid with a given slope of the blind area ≥ 2% from the house.
Thermal insulation width made of extruded polystyrene foam along the perimeter should be no less than the depth of seasonal freezing of the soil.
Horizontal thermal insulation thickness must be no less than 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, thermal insulation from the inside of the room is allowed. Thermal insulation on the room side is carried out either by gluing extruded polystyrene foam to the wall surface using solvent-free compounds (for example, cement-based), or by fastening insulation boards mechanically followed by installation of a finishing layer.
In this case, it is mandatory to check the walls of the insulated structure for the possibility of accumulation of condensation moisture in it.
The construction of a wall with extruded polystyrene foam shows that such a construction is acceptable.
How to attach polystyrene foam
for waterproofing the foundation
The insulation is placed on the leveled outer surface of the walls of the insulated structure after waterproofing has been carried out on it.
When insulating the foundation from the outside, mechanical fixation of EPS boards is not allowed, since in this case the continuous waterproofing coating will be damaged!
Extruded polystyrene foam is attached to the wall surface to be waterproofed with glue or by melting the bitumen waterproofing layer at 5-6 points, followed by pressing the slabs tightly.
Gluing of EPS should begin 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. Re-installation of glued slabs, as well as changing the position of the insulation after a few minutes after gluing, is not allowed.
Thermal insulation boards must have the same thickness and fit tightly to each other and to the base. In this case, they should be placed with offset joints (in a checkerboard pattern). If the seams between the plates are more than 5 mm, they must be filled with polyurethane foam. It is better to use slabs with stepped edges. They are laid close to adjacent slabs so that parts of the L-shaped edges overlap each other. This installation eliminates 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 roll or mastic type waterproofing on a bitumen basis, a special or is used. When choosing an adhesive, you must ensure that it does not contain solvents and does not dissolve the polystyrene foam board during application. For gluing slabs to a vertical surface and for sealing seams, it is not recommended to use conventional polyurethane foam, since due to large volumetric expansion, “heaving” of the thermal insulation layer can occur, or the slabs can be separated from the surface due to the occurrence of large stresses between them.
Below ground level, the adhesive layer can be applied at several points around the perimeter and in the center, so that the moisture collecting between the surface of the slab and the building base flows down unhindered.
It is prohibited to install insulation on bitumen waterproofing that has not yet dried for the following reasons:
- during the installation process, the waterproofing elements may “move apart”, after which the tightness can no longer be guaranteed;
- Waterproofing products based on cold bitumen may contain solvent particles that can damage thermal insulation material. Therefore, when using cold bitumen waterproofing, before installing extruded polystyrene foam slabs, it is recommended to allow the surface to dry for 7 days.
Base insulation
The base should be insulated around the perimeter to reduce thermal bridges and protect the foundation from frost damage and cracking due to thermal expansion.
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, moistened by rain, melt water and splashes of drops.
Facade insulation system based on non-waterproof thermal insulation material, such as expanded polystyrene or mineral wool, should be at a distance of at least 30-40 cm from the top edge of the soil so as not to be exposed to rain and melt water.
To insulate the base, 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.
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 plinth area (above ground level), 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, fastening EPS is only possible using adhesive compositions, then in the above-ground part of the plinth it is necessary to install façade dowels at the rate of 4 dowels per slab.
As a thermal insulation layer above ground level, it is possible to use a special brand of extruded polystyrene foam with a milled surface, which ensures better adhesion of adhesive compositions. 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 brush with metal bristles or a wood saw with fine teeth.
- Fastening the insulation (produced in the same way as fastening the insulation of the entire facade system using polymer-cement glue)
- Installation of the first layer of reinforcing fiberglass mesh
The prepared adhesive solution is applied with a long stainless steel grater onto the slab vertically in the form of a strip. The thickness of the glue should be about 3 mm. The solution begins to be applied from the corner of the house. After applying the adhesive solution on a segment equal to the length of the prepared mesh, it is leveled with the serrated side of a grater until the same thickness of the solution is obtained over the entire surface. You need to apply a prepared piece of mesh onto the fresh adhesive solution, pressing it in several places to the glue with the edge of a grater or your fingers. You need to remember to overlap the edge of the mesh by 10 cm. Using the smooth side of the grater, you need to drown the mesh in the adhesive solution - first vertically from top to bottom, then diagonally from top to bottom.
- Doweling (performed through the first layer of reinforcing fiberglass mesh)
- Installation of the second layer of reinforcing fiberglass mesh (similar to the first)
- Base finishing ( possible options):
- decorative plaster;
- stone slabs(attached with special glue);
- ceramic tile(attached with special glue for decorative tiles).
Insulation of the foundation slab
If insulation is necessary foundation slab Thermal insulation boards are laid on the waterproofing. If it is planned to use knitted reinforcement to reinforce a reinforced concrete monolithic foundation slab or load-bearing floor, then it is enough to protect the insulation slabs from the liquid components of concrete with a polyethylene film 0.15-0.2 mm thick, laid in one layer. If for reinforcement works If you plan to use welding, then a protective screed of low-quality concrete or cement-sand mortar. The film sheets are laid with an overlap of 10-15 cm on double-sided tape.
Nowadays, many people independently build and repair their homes. For anyone who has encountered insulation, EPS means only one thing - extruded polystyrene foam. The range of applications of this material is very wide; in particular, it is widely used for insulating foundations. Extruded polystyrene foam is produced by extruding polystyrene foam through an extruder. Extrusion imparts new qualities to polystyrene that are not possessed by material produced by non-press or press methods.
Scope of application
EPPS is used in civil and industrial construction, greenhouse farming, in household appliances, when constructing highways, runways, and laying pipelines. In the construction industry, EPS is used to insulate all house structures: from the foundation to the roof.
EPPS is one of the best materials for insulation Insulation of foundations for almost all buildings in Russia is necessary measure. According to the climatic zoning map, only in the southern regions of the Russian Federation can one do without this work. In the rest of the area, thermal insulation of the foundations must be carried out, and the further north you go, the larger the layer of insulation must be laid.
Since expanded polystyrene is produced in sheets, it is convenient for thermal insulation of all types of foundations - strip, pile, slab.
Moreover, the strip foundation can be insulated both from the inside and outside. For ease of installation, polystyrene foam sheets have a groove along the edge. For strip foundations, in addition to insulating the foundation itself, insulating the blind area is also important, especially on heaving and moist soils. Therefore, first of all, you need to take care of drainage.
Advantages
Polyurethane foam, polystyrene foam, foam glass and expanded clay are suitable for insulating the foundation. The best is polyurethane foam, but it is more expensive and requires a spraying unit. Among expanded polystyrene foams, the advantage is on the side of EPS.
There are several reasons for this:
- good thermal insulation properties. Thermal conductivity is at the level of polyurethane and is 0.029-0.031 W/m*ºС. Moreover, in a humid environment these properties practically do not change;
- low vapor permeability – 0.005 mg/m*h*Pa. This is not enough for walls, but just right for the foundation;
- minimum water absorption – 0.4%. The walls of the basement and foundation will be dry;
- compressive strength and bending strength are quite high compared to other foams;
- frost resistance – more than 50 cycles. It is used at temperature differences from -70 to +75;
- durability – declared service life is 45 years;
- ease of use. Absolutely light, with a special edge, sheets that can be cut with a knife.
Extruded polystyrene foam is competitive in terms of price. However, it is always worth remembering that EPS is flammable, so you should try to use it outside in places with minimal risks of ignition, and also be sure to insulate it with non-flammable material.
How to choose
When buying EPS, you must definitely ask for a quality certificate. The sheets themselves also need to be inspected. They can be of different colors, but the color must be uniform. It is advisable to break a piece of the sheet; a characteristic crack should be heard. Then look at the structure; regular polyhedra will be visible on the fault lines. When you press on the sheet with your finger, it should spring back, but a small dent may remain.
When choosing EPS for foundation insulation, you need to pay attention to the density. For these works, the density of polystyrene foam must be at least 35 kg/cubic meter. m.
Very important point, how thick should the EPS sheet be? The answer to this question can be found in SP 50.13330.2012, which provides indicators and requirements for thermal protection of buildings.
A key indicator of the thermal protection of a structure is heat transfer resistance. For ease of use, the Rules provide the values of the reduced resistance to heat transfer of enclosing structures, broken down by degree-day of the heating period. For each construction area, the normalized heat transfer resistance is calculated, adjusted by a coefficient that takes into account the conditions of the region.
The heat transfer resistance of the enclosing structure consists of the sum of the thermal resistances of each material (layer) of the structure, taking into account the heat transfer coefficients of the internal and external surfaces of the structure. Thermal resistance is the ratio of the thickness of the structure to the thermal conductivity coefficient of the material of the structure (sq. m*ºС/W), i.e. the structure is homogeneous.
Returning to the question of choosing the thickness of the EPS for the base, you need to use the formula:
δth – thickness of the insulation layer (m);
R0 – reduced heat transfer resistance of the building envelope of the construction area, according to the table taking into account GSOP (sq. m*ºС/W);
δ – foundation thickness (m);
λ – thermal conductivity coefficient of the foundation material (W/m*ºС);
λth is the thermal conductivity coefficient of the insulation (W/m*ºС).
Types and characteristics of EPS
For some time now in Russia extruded polystyrene foam has been called by the name of the company that produces this material. This is how Penoplex, Technoplex, TechnoNIKOL and Ursa appeared. Famous manufacturers Penoplex, TechnoNikol, URSA Eurasia supply construction market high-quality thermal insulation.
Penoplex
Especially for underground structures and structures, the company produces a type of insulation called Penoplex Foundation. The manufacturer guarantees increased strength and ability to withstand loads for 50 years. The declared characteristics of this insulation are characteristic of EPS, however, the thermal conductivity coefficient is slightly higher - 0.03-0.032 W/m*ºС.
The sheets have dimensions of 1200x600 mm with standard thickness from 20 to 150 mm. The average cost of one sheet 50 mm thick is 199 rubles.
Watch the video to see how this type of material is used for insulation.
TechnoNikol
For insulation slab foundation The TechnoNIKOL CARBON ECO SP brand of EPPS is produced. It is characterized by strength, stability in a biologically aggressive environment, and thermal inertia. Service life – 40 years.
The company produces one standard size of this brand - 2360x580x100 mm. The price of one sheet fluctuates around 740 rubles.
URSA Eurasia
The company produces three grades of URSA XPS extruded polystyrene foam. The most suitable for foundation insulation is URSA XPS N-V, since it has the highest compressive strength - 50 t/sq.m. m. However, the temperature regime has been reduced: from -50 to +75.
URSA calls its products slabs, and the dimensions are of this material are as follows: 1250x600 with a thickness of 50,60, 80, 100 mm. The cost of one slab with a thickness of 50 mm is 192 rubles.
The use of polystyrene foam for external use requires reliable sealing plaster mixtures based on cement.
Many owners of private housing prefer to insulate the basement and foundation by covering the outside with polystyrene foam. This allows you not only to save heat in the house, but also to protect the foundation of the building from premature destruction and cracking. In addition, the walls of the basement, if there is one in the project, will always remain dry.
The technology for performing such work is not very complicated. The main thing is to adhere to all the main stages of insulation and not to disturb the sequence of operations.
Before choosing expanded polystyrene as the main insulation material, you should find out all its qualities.
The unambiguous pleasant properties that extruded polystyrene foam has are:
- high frost resistance;
- excellent thermal insulation;
- no toxins;
- low response to chemical influences;
- vapor tightness;
- minimal moisture absorption;
- durability in operation;
- resistant to fungi and rotting.
But there are also several not very pleasant qualities that the material has:
- Flammability - additional treatment with special mastics is required in basement areas.
- Low resistance to physical impacts - requires protection from rodents in the form of a metal mesh.
- Mechanical damage - when backfilling there should be no hard rocks in the soil.
But, despite this, the material is highly valued by professionals, as it is easy to install, convenient to use, and can be easily cut into small pieces. And it costs quite a bit.
Selection of polystyrenes for insulation
When choosing a material for insulation, it is worth considering its three main properties:
- density characteristic;
- the size of the slab layer;
- flammability classes.
It is thanks to these parameters that you can effectively insulate any foundation with polystyrene.
Since expanded polystyrene boards are used as insulation, manufacturers, for the convenience of users, produce products whose thickness is not less than 30 mm and not more than 100 mm. This allows you to combine materials in such a way that the resulting insulation thickness is most suitable for each individual case.
Density characteristics also have their significance. For foundations, it is better to use sheets with a density of at least 35 kg/m3.
Flammability classes are only important for insulating the base and basement. After all, the underground part doesn’t care what kind of polystyrene foam will be used. But for the basement and plinth it is worth purchasing slabs with the addition of fire retardants. This will provide some insulation from combustible elements of the home structure.
Preparatory work before insulation
Initially, it is worth preparing the foundation of the building for insulation operations. And for this you need:
- Clean the base from soil and debris.
- Treat with protective mastics.
If the foundation has just been laid, you just need to expand the trench (pit, place on all sides of the pit) by 45 cm. This will allow you to carry out work on insulating the base from the outside with polystyrene without interference. True, after digging ditches, it is necessary to remove the formwork from the foundation.
The same operations should be carried out for the foundation that has long been used under the building. But the difference here will be the additional cleaning work.
You will have to not only remove soil and adhering remains of vegetation from the foundation walls, but also completely clear it of rust, chipped parts of the mortar, and pieces of external waterproofing.
Now you can start priming external walls foundation. The technology is quite simple and resembles conventional priming of any surface. The difference here is the mastic compositions themselves.
Since the primer at this stage of work is waterproofing before laying the insulation, you should approach the choice of mastic responsibly.
It must be remembered that mastics with organic solvents should not come into contact with polystyrene. Otherwise, it will immediately deteriorate. It is better to use water-based primers.
Foundation insulation with polystyrene
After the primer has dried, you can begin the process of insulating the underground area of the foundation with polystyrene foam. Here, too, the technology is simple. The main thing is to perform all operations as the instructions suggest:
- dilute the adhesive mass in the proportions indicated on the container and let it sit;
- apply the mixture to ready-made cut polystyrene foam slabs, and not to the foundation walls;
- give time for the glue to set on the slab;
- press the prepared sheet to the foundation;
- Check the correct position of the sheet using a level.
You need to start attaching the slab to the base of the house from one of the corners. And only from below. This will make it possible to lay out the sheets more evenly and without large seams.
It is better to use extruded polystyrene foam for such work. Its properties are much better than its analogues.
It is always easier to insulate the base of a building from the outside in pairs. After all, it is often necessary to lay the material in several layers.
It is worth remembering that working with polystyrene requires care and attention. Before you start insulating, it is better to prepare the sheets optimal size, cutting them in advance.
Now it’s worth protecting the insulation from external mechanical damage (rodents, sharp stones). To do this, a fiberglass mesh is placed on the outside of the insulation. It is also coated with adhesive solutions.
Can be used metal mesh or just wooden panels. They need to be secured with dowels from the very bottom of the foundation to the ground level. For maximum effect the network (boards) are plastered with ordinary mortar of small thickness. After the plaster has dried, you can backfill.
Don't forget about drainage. It is always performed when insulating base walls with extruded polystyrene foam.
Insulation of the base and basement with polystyrene
Thermal insulation of the basement floor is not difficult. It is performed in the same way as insulating the foundation of a house. But there are some differences here.
After all, the base is above the ground, and it is also affected by external factors. And besides, in some houses there is no basement in the basement. Therefore, the finishing of such buildings will be simpler.
After the slabs are glued to the walls of the basement, you should let them dry thoroughly. And now it is necessary to strengthen the polystyrene sheets with additional dowels, which have a fairly wide head. Such fasteners will hold the plates on the surface of the base without damaging the sheets themselves.
To ensure that the dowel fits tightly but does not damage the insulation, you need to drill small holes at the joints between the sheets. The length of the holes should be slightly longer than the length of the fastener.
Next, carefully drive a dowel into the hole and insert a nail into it. Hammer the resulting structure into the basement wall. Doesn't matter with a basement ground floor or without a basement - the technological process for attaching the slab is the same.
It is important not to miss: for each slab there should be 3-4 fastenings. This will additionally protect the material from damage during further finishing.
Now it’s worth throwing a painting net over the insulated wall of the plinth. And you can throw a solution on it thin layer. As the solution dries, unevenness will be visible. They can be removed with plaster. And only after that you can perform Finishing work from the outside of the basement.
In order for the functions of the basement to serve as best as possible, it is better to finish the base with ventilation material.
