Styrofoam roof insulation technology. Reliable packaging of a private house for the winter or roof insulation with polystyrene foam Is it possible to insulate the roof with polystyrene foam

05.05.2020

Polymer heat insulators are among the most popular materials for the insulation of roofs of various designs. Roof insulation with foam plastic allows you to quickly install thermal insulation with your own hands.

Material Features

Styrofoam is expanded polystyrene - a lightweight material, 98% consisting of air bubbles glued together, which are enclosed in a polystyrene shell. The benefits of styrofoam include:

minimum weight (insulation does not add serious loads to the roof structure);
low coefficient of thermal conductivity due to the high content of air, which is an excellent heat insulator;
resistance to moisture (can be used in a humid environment without loss of thermal insulation properties);
resistance to temperature extremes;
fire safety (the material does not ignite; upon contact with an open fire, it begins to melt);
environmental safety and hypoallergenicity;
resistance to biological damage (the fungus does not develop, is not damaged by rodents);
ease of processing tools and installation;
no tendency to deformation;
long service life (25-80 years);
affordable cost.

Styrofoam is one of the materials that are sensitive to external influences. It must be transported with care. The material must be protected from mechanical damage and exposure to direct sunlight.

When choosing foam for roof insulation and building structures it is important to take into account the technical characteristics of the material of various grades. Manufacturers recommend using foam:

PSB-15 (density 15 kg / m 3) 50-100 mm thick for thermal insulation pitched roofs, including attic, as well as ceilings;
PSB-25 (density 25 kg / m 3) 50-100 mm thick for wall insulation;
PSB-35 (density 35 kg / m 3), or extruded polystyrene foam - for thermal insulation of flat roofs, attic floors, floors. Such material can withstand high mechanical loads.

Disadvantages of foam as a heater

Often the question arises, is it possible to insulate the roof with foam? Polystyrene vapors are toxic, but the finished material does not emit harmful substances. Polystyrene boards can present some danger when melted under the influence of an open flame. But it is worth noting that self-extinguishing foam plastic is used for the insulation of residential buildings - it does not support combustion and belongs to fireproof materials.

Expanded polystyrene sheets can be used to insulate pitched roofs, but in terms of functionality they are inferior to cotton wool insulation: rigid plates made of polymer material cannot always tightly fill the space between structures, as a result of which cold bridges form in places where there are voids and moisture condenses. Processing joints with construction foam or sealant does not guarantee one hundred percent protection. Condensation causes destruction wooden structures and metal fasteners.

The soundproofing qualities of expanded polystyrene are rated quite high, but for thermal insulation of "noisy" metal roofs it is not quite suitable, as it dampens the sound worse than cotton insulation.

Heat insulators made of polystyrene

What is the difference between roof insulation with extruded polystyrene foam and foam insulation? According to the principle of installation, there are no special differences, since both materials are polymer foamed plate insulation. But despite the close chemical composition, extruded polystyrene foam and foam plastic differ in their performance characteristics.

Styrofoam is made by repeatedly exposing polystyrene to water vapor. The initial granules significantly increase in volume and sinter together. It should be noted that the physicochemical bonds between the granules are rather weak, as a result of which the foam plastic has a low fracture strength and can crumble into granules under external influence.

The extrusion method consists in the fact that the polymer granules are first melted and then treated with freon and carbon dioxide. Due to this, extruded polystyrene foam has a strong, integral microstructure, which is small closed cells filled with gas molecules. The cell walls form a continuous mass of matter. Extruded polystyrene foam is a modern high-tech durable material that surpasses traditional polystyrene foam in its functional parameters. This should be taken into account when choosing a material for thermal insulation of the roof.

Penoplex is one of many trademarks extruded polystyrene foam. Today, the term "penoplex" has become a household name and is often used to refer to expanded polystyrene obtained by extrusion.

Basic principles for installing foam insulation

Styrofoam should be laid on a clean and dry surface. In principle, this material can only be installed complete with waterproofing, but in order to ensure long-term operation of the roof, it is advisable to add a vapor barrier layer, otherwise condensate will begin to accumulate on the insulation from the inside. The foam itself will not suffer from it, but wooden structures can begin to rot, become moldy.

Roof insulation with polystyrene foam can be performed different ways, including:

gluing (on liquid nails, facade frost-resistant adhesives, mastics);
mechanical fastening (anchors, wooden slats, umbrella nails);
flooring;
investment in the crate.

Mounting methods can be combined if necessary.. For example, sheet insulation is inserted into the crate and additionally fixed with a dowel with a thermal head (umbrella nail). Or the material is glued to the surface and fastened with screws.

Pitched roof insulation

The choice of a heat insulator is recommended to be made at the design stage of the roof so that the pitch of the rafters matches the width of the sheet material. If we insulate the roof with foam, then this approach can significantly reduce material consumption. The construction market presents sheet polystyrene foam insulation, which can be laid without gaps between the rafters with a step width of up to 2 meters.

In addition, it is important to perform a heat engineering calculation taking into account the climatic features of the area in order to determine the required thickness of the heat-insulating layer. The minimum recommended parameter is 100 mm.

Foam boards are laid on the crate between the rafter legs. For reliable fastening, you can use glue and dowels. Small gaps often remain between the slabs and rafters. They should be blown out with high quality mounting foam or fill with sealant, otherwise cold bridges will form in these places, where condensate will accumulate and adversely affect the wood of the elements truss system. At the next stage, it is recommended to lay a vapor barrier, and then finish with drywall, clapboard or wood board.

flat roof insulation

Expanded polystyrene slabs are a popular option for external insulation of flat roofs. The base of the roof should be well cleaned and covered with a waterproofing film. Expanded polystyrene boards can simply be laid flat, glued, fastened with dowels. It is very important to lay the plates without gaps, as tightly as possible..

The vapor barrier membrane can be laid under the heat insulator on concrete base, then polystyrene foam plates are mounted, covered with a layer of expanded clay, on top of which a cement-sand reinforced screed is laid. Expanded polystyrene as a heater can also be part of such a roofing pie:

reinforced concrete base;
bitumen-polymer waterproofing;
plate heat insulator;
geotextile;
gravel backfill.

This allows you to create an exploitable roof, designed for high loads.

There are more complex versions of the roofing cake, the top layer of which is the soil for planting. Roof insulation with foam plastic is widely used to create such inversion roofs.

Flat roof insulation from the inside

During operation, it may turn out that a flat roof needs additional insulation. In order not to dismantle the roofing pie, it is recommended to insulate the roof with foam plastic from the inside. It is necessary to choose a heater of the required thickness.

Expanded polystyrene sheets can be attached to a reinforced concrete ceiling with glue and dowels. It is important to prepare the substrate surface to ensure high adhesive adhesion. When laying the plates, the elements should be tightly adjusted to each other. It is advisable to use a sealant in the process so that there are no voids at the joints between the sheets and at the interface with the walls.

To finish such a ceiling, you can use a tension or hinged system. If plasterboard or other materials are to be sheathed, a wooden crate is first attached to the ceiling, the thickness of which should not be less than the thickness of the insulation.

The technology of roof insulation with building foam plastic has been known since such a product as styrofoam (the brand name of foam plastic) appeared on the market. For more than 50 years, this method of roof insulation has not lost its relevance, since the technology is simple and affordable, and raw materials have a number of advantages compared to other materials.

Material selection

Depending on the composition of the raw materials used for the manufacture of foam, as well as on the production technology, the material can be classified as follows:

Polyurethane. Made on the basis of polyurethane, consisting mainly of an inert gas. A distinctive characteristic is high density.

Rice. 1. Polyurethane foam sample

PVC. The rigid cell material is a thermoplastic polymer that contains up to 56% combined chlorine, which provides the product with low flammability.

Rice. 2. PVC foam sample

Phenol-formaldehyde. Made on the basis of phenol-formaldehyde resins. The product is characterized by high thermal stability and resistance to solutions of alkali metal salts, acids and weak alkalis.

Rice. 3. Phenol-formaldehyde foam sample

Carbamide-formaldehyde. Having a fine-mesh structure without large bubbles. A distinctive characteristic is the low heat transfer capacity and resistance to the effects of microorganisms and rodents.

Rice. 4. UF foam sample

Polystyrene. Gas-filled foams with high performance thermal conductivity and water resistance.

Rice. 5. Sample of polystyrene foam

All types of styrofoam are suitable for roof insulation, since the main criterion for choosing a material is its thermal conductivity, resistance to changes temperature regime and water resistance. All of the described types of product have technical specifications material suitable for use as insulation.

Advantages and disadvantages

Styrofoam as a heater has a number of advantages over materials of the same purpose. The following list shows just a few of them:

Ease of installation. Processing and laying sheets does not require special knowledge and professional skills of the builder. To carry out the installation of the material under the power of everyone. professional tool it will not be required.
Resistance to self-destruction processes. Polyfoam is difficult to rot, which significantly increases its operational period.
Low mass. In addition to ease of installation little weight material allows you to insulate the roof without weighing the structure.
Low thermal conductivity. Among all existing heaters, foam plastic is characterized by the lowest heat transfer capacity. The sheet temperature remains stable at the + mark even at ambient temperatures up to 60°C.
Stable dimensions. Throughout the entire operational period, the material retains its shape and dimensions, which protects the insulation layer from the appearance of gaps.
soundproof characteristics. The material has a high level of noise suppression. It can be used for the purpose of soundproofing rooms.
Ecological purity. Despite the fact that the vapors of the feedstock are poisonous, in the form of the final product the material does not cause harm and belongs to the class of environmentally friendly materials.

The disadvantages of the insulation include its vapor tightness and flammability. Before insulating the roof with foam, you need to take care of the ventilation system.

Roof insulation technology

The process of laying insulation can be divided into several stages, the first of which is the preparation of the roof for work.

Roof preparation

The process consists in the thorough removal of moisture from the entire surface of the crate and the roof as a whole. It is advisable to dry the wood with a building hair dryer in order to avoid the formation of condensate.

Rice. 6. Removal of floor moisture

Laying a hydrobarrier

The service life of the roof directly depends on the installation of a special film. The hydrobarrier must protect the insulation layer from the penetration of moisture inside. Styrofoam will not suffer from exposure to water. The risk exists for wooden structures that are subject to the process of decay and destruction.

The installation of the film is carried out along the logs, horizontally from the eaves to the ridge from top to bottom. Be sure to have an overlap between the strips of the film. The material must be fastened with staples or nails.

Rice. 7. Laying waterproofing material

Installation of thermal insulation

Roof insulation with building foam from the inside construction is carried out by attaching sheets of material to the crate between the rafters. For a good coupling of two surfaces, along with special dowels, it is customary to use glue. There is a high probability of the formation of gaps between the insulation sheets and the lags. They must be eliminated by applying mounting foam or sealant. If this is not done, the holes will cause condensation to form inside the insulation, which will ultimately reduce thermal insulation and lead to rotting of the elements. roof structure.

Rice. 8. Installation of insulation

Flat roof external insulation technology

A flat roof, unlike a sloped roof, can be insulated from the outside. For this, the basis roofing material thoroughly cleaned and dried, which is a preparatory stage of work on insulation.

The second stage is the laying of waterproofing material. In the case of a flat roof, this process is much easier: it is enough to evenly distribute the film over the entire insulated surface, carefully fixing it at the joints.

Rice. 9. Installation of a hydro-barrier on a flat roof

Next is the installation of insulation. It must be spread evenly around the entire perimeter of the roof and secured with dowels or glue. The quality of the insulation depends on the packing density. It is necessary to avoid the appearance of gaps between the plates. When such are formed, it is better to eliminate them with mounting foam or sealant.

Rice. 10. Laying foam on a flat roof

To increase the wear resistance of the structure, a layer of vapor barrier material is laid on top of the heat insulator, after which the roof surface is covered with bulk material. The last step in the insulation is a concrete screed.

Technology of internal insulation of a flat roof

When asked whether it is possible to insulate a flat roof with foam from the inside, the best answer would be a description of the technology, which consists of three stages:

preparation of the roof surface;
installation of an insulating layer;
insulation fixing.

Holding preparatory work involves thorough cleaning and drying of the roof surface. When insulating a flat roof, the quality of this procedure affects the degree of strength of the foam fixing: a detailed surface provides sufficient adhesion of materials.

Rice. eleven. Internal insulation flat roof

The procedure for installing a hydro-barrier does not differ from the technology used for insulating a roof located at an angle. You can do it yourself.

The fastening of the heat-insulating layer, as in the case of a sloping roof, is carried out with the help of glue and dowels. However, it should be taken into account that when installing the finishing layer of the ceiling, the load on the insulation layer will increase, so it must be fixed very carefully. The ideal option decorative finishes the ceiling will be the installation of a suspended structure. In this case, it is better to strengthen the roof frame by mounting a control profile.

Do-it-yourself roof insulation

To the question whether it is possible to insulate the roof with foam plastic from the inside with your own hands, the answer is clear: Every interested person can carry out the procedure. In this case, the main thing is to make accurate measurements. Ideal will be the insulation, which is planned during the development of the roof project. Then it is possible to calculate the distance between the lags so that during the installation of the insulation boards there are no gaps and cracks between the wood and the foam. A pre-planned insulation project saves on sealant costs.

Mistakes of the master or what not to do

In order not to violate the technology of roof insulation with building foam, it is necessary to avoid laying deformed slabs. If damage to the sheet occurred at the time of fastening, it is necessary to replace it with a whole one. The presence of cracks in the insulation material will lead to the penetration of moisture and cold. This will adversely affect the wooden structural elements.

It is advisable not to use a material whose width does not correspond to the distance between the roof joists, since this causes holes and impairs the tightness of the layer. Gaps must be sealed to prevent leaks.

Rice. 12. Elimination of leaky seams

As a layer that isolates moisture, it is better to use a special material, such as Hydroisol. The use of a conventional film will not be able to fully protect the structure from moisture penetration. The same applies to the vapor barrier layer, it is better to use a vapor barrier membrane. Compliance with the norms during installation will extend the life of the roof. The minimum service life of polystyrene as a heater is 15 years.

Are you attracted to foam roof insulation as the cheapest and easiest option, but are you worried about some opinions about its toxicity, and you really do not know how to proceed with this material?

In this article, we will reveal the 5 most important questions about polystyrene foam as a heater and help you understand the technology of its installation with the help of detailed master classes. It will be interesting!

Styrofoam is the popular name for expanded polystyrene. But it is worth distinguishing between simply expanded polystyrene and extruded polystyrene foam.

Polystyrene is a product of the polymerization of styrene, which is quite clear from the name alone. In appearance, polystyrene is hard, resilient and colorless. It does not have high mechanical bending or tensile strength, low density. Even lenses are made of this substance, not to mention dishes and other household items.

Expanded polystyrene is expanded polystyrene, which is produced in the form of sheets up to 20 cm thick and can be of different density. It costs much less than extruded polystyrene foam, is more loose and has a more limited scope.

The name of extruded polystyrene foam comes from the method of its production - extrusion, when the raw material is squeezed out through certain holes of the same size. Even more precisely: extruded polystyrene foam is a gas-saturated polyethylene melt. It is produced in the form of sheets with a thickness of 30 to 70 mm, it can be different not only in density, but also in color. It is much more durable compared to conventional foam plastic, has a tongue-and-groove system along the edges and is easy to install - there is no need to fill joints. In addition, its thermal conductivity is even lower - in fact, the lowest of all existing heaters.

Extruded polystyrene foam is made by extrusion, due to which it has a uniform closed-cell structure. Each cell is no more than 0.1-0.2 mm in diameter.

Extruded polystyrene foam in English is called XPS, in Russian - EPPS. They are also insulated with polystyrene as a sandwich panel, when this insulation is closed from above with an OSB plate or a metal sheet:

Moreover, working with this material is quite simple:

But one of the most sought after XPS products on Russian market– light blue Primaplex boards. This is a fairly durable material with extremely low water absorption, dimensional stability and high frost resistance.

Why is polystyrene better than other thermal insulation?

And now let's deal with popular myths about polystyrene foam.

So, the first and most important quality for which this insulation is valued is high thermal insulation. This is a coefficient of 0.035-0.048 W / mK at 25 ° C, and 0.20 W / mK for its individual types, according to manufacturers. But absolutely all foamed plastics are afraid of water and quickly absorb it. And expanded polystyrene, which is made using the non-press method, has a water absorption of up to 350% of its mass. And even this is not the limit! And the more moisture in the insulation, the lower its thermal insulation properties.

But in practice, as a roof insulation, ordinary polystyrene foam lives only 10-15 years, after which its heat-shielding qualities decrease sharply. But extruded polystyrene foam, abbreviated XPS, is more durable.

But the foam has the lowest thermal conductivity among all existing roof insulation. Even with severe frost the temperature of foam and XPS sheets with a thickness of 50 mm will be + 5 ° C. Plus such advantages over other heat insulators:

Soundproof.
Stable dimensions all the time.
Ease of installation and cutting to the desired size.
No need for wind protection.
Resistant to various chemicals.

And quite interestingly, in the factory, they test the strength of extruded polystyrene foam: they lower it into water, heat it up to + 40 ° C and cool it down to -40 ° C. Each such cycle is equated to one year of operation. Therefore, manufacturers confidently declare that extruded polystyrene foam can serve as a roofing insulation from 50 to 80 years.

And the most important advantage of extruded polystyrene foam is that it does not reduce its thermal insulation properties even when in contact with water. Whereas ordinary heaters work conscientiously for only a few years, and then, if mistakes were made in the insulation of the roof, they gradually reduce their thermal insulation qualities and the house has to be heated more and more. This is not to mention other related problems.

But in roofing cake polystyrene foam can be damaged by rodents: they will not live in it, but they will make moves. Is it possible to hide these sheets from the outside:

Is styrofoam safe as a heater?

Officially, this material is classified as environmentally friendly, i.e. those that do not pollute environment and are not dangerous to humans. But let's first determine what effect on the human body can be considered dangerous, and what - prejudice and unnecessary anxiety. You will be greatly surprised!

Such different concepts

So, in the world it is customary to refer to two main concepts for assessing the harm to the human body of certain substances: threshold and linear.

The threshold concept states that all harmful substances in a residential building must be reduced to a certain level for each of them, a threshold, which is fixed by the MPC value (maximum permissible concentration). Those. This is the amount of a harmful substance in the air that can already harm a person. Exceeding this threshold always leads to such negative consequences as illness or even death. Let's give an example: the cheapest foam was chosen as a heater, it was installed incorrectly, there is no normal ventilation in the dwelling. Result: diseased liver in the household. But in a well-ventilated house of harm long time nobody feels. Those. we are talking that the concentration of a harmful substance below the established threshold does not have a dangerous effect on a person, and a healthy body can easily cope with small toxins. It's like breathing in cigarette smoke from the interlocutor once.

All countries of the former USSR and modern Russia building codes are based on the threshold concept. But in Japan, Canada, Germany, the USA and Belgium, a linear concept is at the head, the essence of which is that the harmful effect on the human body linearly depends on the total absorption of a certain substance. Those. at one time, cigarette smoke really will not have a significant negative impact on the body, but constant smoking - yes. The same applies to polystyrene: if such a heater is both on the roof and on the walls, then every day a person absorbs the allowable rate of styrene through the lungs, which is not so little in a year. In a word, low concentrations of poison at long-term use are also harmful. It is easy to show this using the example of modern megacities: all transport emissions and emissions from factories do not exceed the sanitary threshold, but still, the life of the citizens is not sweet.

If, when insulating, one adheres not to the first concept, but to the second, then the value of the maximum admissibility of styrene in a residential building will have to be reduced by 594 times!

Of course, polystyrene is used both in the food industry of our country and in medicine. But remember that its toxicity is calculated according to the same concept - the threshold. Let's just note that polystyrene and polystyrene are already being phased out in many countries, and in some even banned.

Substance that is not excreted from the body

And now we recall that styrene is a condensed aromatic compound that contains benzene yards in its molecule and is bad because it is not excreted from the human body. And, according to modern scientists, in housing construction, the threshold for the presence of styrene in the air should be reduced to such minimum values that any polymerization products (including polystyrene) should be prohibited.

Therefore, we conclude: styrene is toxic to humans, primarily because it accumulates in the liver. After all, the problem is precisely that the human body can really cope with an ordinary toxin, simply by processing it with the help of the liver and throwing it away naturally, but styrene is not excreted from the body - it only accumulates. Therefore, the threshold concept cannot be applied to foam insulation - only linear.

In addition, according to modern SNiPs, for combustible materials, toxicity indicators of combustion products must be determined. And for high-quality polystyrene foam, this value is T2, which means "moderately hazardous."

99% polymerization

There is another point that not everyone knows about. The fact is that 100% EPPS polymerization is only a theory, but in practice it does not even reach 98%. In addition, even the polymerization process itself is reversible, because polymers are easily destroyed by ultraviolet rays, ozone, water, oxygen, heat and mechanical stress. Then free styrene begins to separate from the EPPS and penetrates into the living quarters, albeit in a small concentration, but on the heart and women Health influence and not a little. And the most frequent problems from this element - toxic hepatitis, and all because of the cumulative properties of styrene accumulate in the liver, but not excreted.

And, finally, special studies of the Russian Academy of Sciences have shown that during its period of operation, expanded polystyrene decomposes up to 10-15%, and 65% of the decomposed part consists of styrene.

Exit - ventilation!

But how can polystyrene, which is used to insulate the roof, harm? If this is insulation from the outside, then, of course, nothing. If from the inside, but the attic is not used, then ventilation must be carefully considered. But if we are talking about a residential attic with such insulation, then things are bad. At least we don't advise you to do that.

Or it’s good to close the foam in front with another heater, as in this project:

How to insulate the roof with foam inside and out?

But to answer this question, we have prepared a series of detailed master classes for you.

The main methods of attaching foam to the surface:

But basically two methods of fastening are popular. Adhesive:

For screws:

That's the right way to insulate mansard roof:

As a concrete roof insulation:

Here is the first stumbling block that can upset you when insulating the roof with foam. This is the concept of expansion joints. Seams form over time thermal insulation materials due to temperature changes, as well as around the perimeter and in the places where the beams pass. You can notice such problem areas in winter - along a thin strip of ice or snow that does not roll down. And there is a limit to the deviation from the norm of these seams, and for pitched roofs it is one, and for flat roofs it is completely different.

Although some home craftsmen simply cut the foam to the size of the rafters and insert it without any seams:

Nuance 2. Weathering

But the most alarming thing is that expanded polystyrene undergoes weathering, during which gas-containing mixtures are formed. And weathering in an ordinary attic with its ventilation through oppositely located dormer windows– is inevitable. Even residential attic it is undesirable to finish with expanded polystyrene, so that in the heat you simply do not breathe in the so-called persistent organic pollutants, which, by the way, are strictly prohibited by the Stockholm Convention in Western countries.

Nuance 3. Preliminary plan

Unlike the installation of conventional heaters, before installing foam sheets, you should carefully consider the plan and make sketches. There are other difficulties: for example, such panels cannot be cut and processed mechanically, they cannot be fixed with screws - only inserted into finished structure. Moreover, if you need to carry out certain communications under the roof (the same electricity, for example), then you will have to organize another mounting layer under the panels, at least 50 mm thick.

Nuance 4. The need for waterproofing

Although Styrofoam and Styrofoam are waterproof, covering roof slopes or flat roofs with them cannot be considered waterproofing. All because of a large number seams. That's why a waterproofing layer is needed: it can be bituminous roll materials, oiled paper, fiberglass or sulphate kraft paper.

Still decided to insulate with this material? think over proper ventilation roofs and take care of your health!

Styrofoam roof insulation is one of the most popular ways to insulate a house, used for both pitched and flat roofs. In addition, foam can be used to insulate floors attic floor. Styrofoam as a heater has many advantages: it is easy to install and process, is not afraid of moisture, does not rot and is destroyed by microorganisms, provides good thermal insulation without weighing down the structure.

Polyfoam also has disadvantages. These include vapor tightness and flammability. Therefore, when insulating the roof with polystyrene foam, it is necessary to take care of the ventilation of the attic room and compliance with all fire safety standards.

Principles of foam roof insulation

As in the case with, when the roof is insulated with foam plastic, the heat-insulating layer has the form of a multilayer “pie”, in which there is necessarily a waterproofing film on the side of the roof and a vapor barrier on the side of the attic room. Although the foam does not have the ability to accumulate moisture, the ingress of water and water vapor into the insulation layer is highly undesirable - rafter beams and other wooden structural elements begin to rot.

In general, the sequence of roof insulation with foam plastic looks like this: laying waterproofing material on the rafters before or during the laying of the roofing, fixing the foam boards between the rafters or under them, sealing the seams with mounting foam and eliminating cold bridges, laying vapor barrier, finishing internal walls and attic ceiling.

In addition to insulating the roof itself, polystyrene is also used to insulate floors, that is, the attic floor. In this case, it is laid on a subfloor, on a pre-laid layer of vapor barrier film, and covered with a plywood layer, waterproofing and decorative coating on top.

When buying polystyrene foam, it is necessary to choose plates of such a size that the number of joints is minimal. The thickness of the foam for insulation should be at least 10 cm, any density can be taken, while it should be taken into account that with an increase in density, its mechanical strength and heat-insulating properties increase. Styrofoam practically does not have soundproofing properties, therefore, for a residential attic, it is also necessary to provide a soundproofing layer of at least 5 cm, laying it under the decorative sheathing. This is especially true for roofs covered with profiled sheet or metal tiles - when it rains, the sound of drops can be heard quite clearly.

In addition to polystyrene, polystyrene boards can also be used. They have the same advantages as polystyrene, while they have greater strength, do not support combustion, and are resistant to damage by rodents. The price of polystyrene is slightly higher, but because of the better heat-insulating properties, plates of smaller thickness can be taken.

Styrofoam roof insulation technology

Roof insulation with foam plastic can be carried out both when laid roofing as well as with the roof open. In both cases, thermal insulation begins with the laying of a waterproofing film. It is better to choose a special film, for example, for roofing. It has a membrane structure and releases water vapor in one direction - from the inside of the heat-insulating "pie" to the outside. The film is placed on the rafters without pulling it. Film sagging is allowed. The roll is unwound across the rafters for the entire length of the roof, while it is necessary to ensure that the film is facing the smooth water-vapor-tight layer outward. The following strips of film are overlapped by at least 10 cm, and the joints are glued with special adhesive tape. There must be an air gap between the film and the crate, so a 50 mm bar is nailed to the rafters on top of the film, and on top of it - the crate boards, on which the roofing is laid.
Foam boards are usually laid in the space between the rafters, trying not to leave gaps. The size of the plate is cut with a clerical or other thin sharp knife along a metal ruler. Styrofoam can be fastened to the rafters using auxiliary rails or polystyrene glue. If the rafters are made of timber or boards, the foam can be glued to the plane of the rafters with glue. If the rafters have round section, bonding with adhesive may not be sufficient. In this case, a filing is made from a board that holds the plates in two or three places, and the voids between the plates and other structural elements are foamed.
It is very important to carefully close all the cracks to prevent the formation of cold bridges. Temperature fluctuations inside the heat-insulating "pie" lead to the fact that condensation forms in places subject to cooling, as a result of which leaks may form or the rafter system may begin to rot. In order to exclude cold bridges, the foam can be laid in two layers apart, overlapping the joints of the first with the second layer. Between themselves, the layers are fastened with glue.
If soundproofing of the attic room is necessary, soundproofing mats made of fibrous materials are placed on top of the foam. Fibrous materials lose their properties when wet, so they must be covered with a vapor barrier.
The insulation must be isolated from the interior of the attic with a vapor barrier anti-condensate film. It is overlapped, carefully gluing the joints and fastened with a furniture or construction stapler to the rafters or filing.
Guides are required for fastening the skin - wooden blocks or profile. Their thickness should provide a ventilation gap of 3-5 mm between the vapor barrier and the sheathing. As a skin, it is better to use natural materials that are not prone to condensation. In addition, when insulating the roof with foam, it is necessary to equip exhaust ventilation and an adjustable heating system to prevent waterlogging of the attic walls in wet weather.

When insulating foam floors, the technology is similar to roof insulation. At the same time, it should be remembered that the bottom layer separating the insulation layer and the subfloor must necessarily be a vapor barrier film with anti-condensation properties, and the top layer, on which the finishing floor is laid, must be a waterproofing film. It will protect the insulation from waterlogging in case of water leaks. At the same time, foam plastic plates are laid in the gaps between the ceiling beams, foaming the cracks. The foam plastic can not be attached to the beams, it will be pressed by the finishing floor.

The foam is not highly resistant to point loads, so when using linoleum, cork or thin laminate as a coating, it is necessary to close the foam with moisture-resistant plywood or drywall. On top of the foam, you can also perform concrete screed in which to lay - this will ensure uniform heating of the attic room and regulate the humidity, which will allow maintaining an optimal microclimate there.

Market modern materials for the insulation of low-rise buildings is actually divided into two camps - adherents of mineral fiber insulation and those who prefer foam materials. If many years of experience in insulating roofs and floors with mineral fiber speaks for itself, then roof insulation with foam plastic is not yet so popular among developers and construction companies, although such an attitude is clearly undeserved. There are many reasons for a reserved attitude towards foamed polymers, therefore, before answering the question for yourself whether it is possible to insulate the roof with foam, it is worth understanding them in more detail.

Why use styrofoam for roof insulation

From time immemorial, thick mats made of pressed mineral fiber have been used to insulate the roof. Everyone who has worked with mineral wool at least once in their life will confirm my words: even when using protective equipment, working with such a heater is far from sugar. In addition, if a hole forms in the roof, the waterproofing is damaged, or condensate flows into the body of the fiber insulation, all work is in vain.

In this sense, roof insulation with foam plastic is just a gift of fate:

Lightweight and strong foam boards can be laid under rafter battens two to three times faster and easier. Even if the foam fell under a downpour or lay in an unheated attic for a couple of years, it has not lost its qualities and can last for several more decades;
Allows you to get higher thermal insulation parameters, already with a sheet thickness of 15-17 cm, heat loss through the roof slopes can be reduced to 97%;
Repair and replacement of roof insulation, if necessary, is five times faster than using mineral wool.

Note! The cost of insulation square meter roofs will cost 30% less than when using mineral slabs.

The material is easily cut with a knife or hand saw, does not delaminate, normally does not absorb or emit volatile substances or odors. It can be glued, painted, treated with special primers and even plastered with cement-sand or gypsum mixtures.

Logic suggests: if walls are insulated from foam plastic both inside and outside the room, houses are built from sip panels based on foam plastic and polystyrene foam, so why can't foam sheets be used to insulate the roof?

The answer sounds quite simple - foam plastic has its own characteristics and disadvantages that must be considered when planning roof insulation.

Features of the arrangement of foam roof insulation

Expanded polystyrene, which is foam, has its own hidden disadvantages that must be considered before insulating the roof with foam:

The foamed polymer practically does not conduct water vapor, therefore, to prevent flooding of the wooden elements of the roof truss system, it will be necessary to close the insulation layer from the side of the attic room with a vapor barrier film;
Similarly, the plane of the foam sheets on the side where the roofing material is attached must be covered with a waterproofing sheet or film;
The main disadvantage of foam, preventing widespread use foam material as the basis for insulation, is its weak thermal resistance and flammability.

Note! The foam manufacturer tried to minimize the susceptibility of the foam to ignition by using special additives in the form of iron and chromium salts.

Such grades of foam, even when in contact with an open flame, melt, emit decomposition products of polystyrene, but a stable combustion front at temperatures up to 370-400 ° C is not formed. Wood, widely used for the manufacture of roof rafters, already at 270 ° C begins to char and smolder steadily. Therefore, for the arrangement of roof insulation, it is recommended to use foam grades with index C.

For the arrangement of insulation systems, foam plastic with a density of 20 to 45 kg / m 3 is used. The heaviest brands have always been the most durable and, accordingly, the most expensive. The lower the specific gravity, the lower the thermal conductivity, but the strength of the material also decreases.

Since the foam sheets laid in the roof insulation truss system do not experience stress, as, for example, when arranging a concrete floor, there are no special requirements for contact or bending strength. But this does not mean that almost any material can be used to insulate the roof, for example, sheets from foam packaging or a thermal insulator for industrial refrigerators. This foam will crumble into granules in the second or third year of service. Use for insulation foamed polystyrene grade C with a density of 30 kg / m 3.

Styrofoam-based roof insulation technology

The sequence of laying an old, long-built house may differ somewhat from the scheme for arranging insulation on a newly assembled rafter system of a new building. The difference lies in the use and location of the waterproofing film or membrane. Of course, the work on laying the foam insulation system is carried out only after processing all, without exception, wooden parts roof truss system.

Arrangement of insulation for an old building

Most often the question effective insulation rises specifically for houses whose roof is assembled in ready-made and has been working well for quite some time. In such a roof, as a rule, there is already a layer of insulation laid down during construction. If the revision showed the good condition of the materials used, the absence of blocking or destruction of the vapor and waterproofing, then you can simply supplement the existing layer with upholstery OSB boards and a sticker of an additional layer of foam plastic 70 mm thick. The laid insulation can be covered with a layer of aluminized film.

Remains of waterproofing and insulating roof material are removed;
The surface of the wood of the rafters and battens is thoroughly cleaned with an electric brush, after which it is treated with protective antifungal compounds;
A new layer of waterproofing is stuffed onto the crate and rafters, even the rafter beams must be wrapped in insulation and secured with a stapler;
Polystyrene blocks are cut with a width equal to the pitch of the rafters, polyurethane glue is applied to the end surface, and the material is laid on the inside of the roof like bricks.

In the lower part of the roof, it is necessary to lay foam with a minimum number of seams; in the area of \u200b\u200badjacent to the ridge, insulation can be collected from pieces and scraps, but it is imperative to glue and foam the seams. Styrofoam up to 50 mm thick can be easily cut with a knife; for thicker plates, it is best to use a carpentry saw with teeth ground off the sides. In this case, the cut is thin and neat.

The smallest dust and foam balls, when cut, are highly electrified and stick to the hands, therefore, when cutting the material, a vacuum cleaner is usually used to collect chips. It is advisable to work in an apron and oversleeves, since dust, balls and the smallest pieces of foam are very difficult to remove from the surface of clothing.

Excess foam is trimmed and protected. After laying, a vapor barrier material is applied to the surface of the insulation layer. Best to use roll material with an aluminized surface like penofol or isopol. The vapor barrier is covered with lining from lining or moisture resistant plywood treated with flame retardant composition.

Roof insulation with polystyrene foam for a new building

The technology for the construction of insulation for a newly constructed building differs only in the method and place of attachment of the upper layer of waterproofing. The film or membrane is rolled out in horizontal stripes on the roof rafters after the crate is stuffed. The laying of the canvas begins from the lower edge of the roof slope, each subsequent row is laid out with an overlap of the previous one. The material is fixed with a stapler to the rafters, the joints must be glued with adhesive tape. A counter crate is stuffed over the membrane to form vents. The remaining elements of insulation are performed similarly to the previous case.

Most important point building an insulation system is the arrangement of the node for passing the roof covering chimney. It does not matter what material the chimney pipe is made of, it will have to be insulated with basalt fiber and covered with a sheet metal protective casing. The box in which the pipe is attached to the rafters is also filled with a mineral thermal insulator, the crate or lining covering the foam layer in close proximity to the pipe, at a distance of 40-50 cm, must be sewn up with a metal sheet.