Is it possible to insulate a roof with polystyrene foam? A quick way to insulate a roof with polystyrene foam using special technology

The process of insulating a roof with foam plastic is a very popular way to insulate a house. Both pitched and flat roofs can be insulated in this way. Also, foam plastic for insulation can be laid in the attic floors.

Roof insulation with foam plastic has many advantages: it is easy to install and process, it is not afraid of moisture, it does not rot or be destroyed by microorganisms, and it can provide reliable thermal insulation without adding weight to the structure.

But the material also has disadvantages - vapor permeability and flammability. Therefore, when using polystyrene foam as insulation, it is necessary to install ventilation in the attic space and strictly observe all fire safety standards.

Difficulties with foam insulation

Many developers often have a question: are foam vapors poisonous? Is it worth using this material to insulate the roof from the inside? The benefit of polystyrene foam is the fact that polystyrene foam (PSB) used for thermal insulation in residential premises is self-extinguishing - it does not catch fire. The flammability class of polystyrene foam is category G1, that is, it is a fireproof material.

While working on pitched roof many experienced builders use mineral wool or basalt slabs. This choice is determined by the rigidity of the foam, due to which the material cannot be located in the entire space under the roof. Voids appear into which cold penetrates, resulting in the formation of condensation. Destroys due to condensation rafter system, and rust metal elements in the roof.


To avoid condensation, when choosing foam plastic for thermal insulation of the roof of a private house, it is necessary to clarify such an indicator as the thickness of the thermal insulation layer for the area in which you live. When making calculations, you need to focus on the type of used roofing material And climate zone. The choice of foam has one thing in common: it is not recommended to use foam with a thickness of less than 10 cm for work.

Expert opinion

Konstantin Alexandrovich

Ask a question to an expert

In cases where the insulation needs to be laid in two layers, and the thickness of the rafters does not allow it, it would be correct to lay a 50mm by 50mm beam horizontally, step under the covering material (plasterboard, OSB and various moisture-resistant boards).

Characteristics of foam plastic


Foam plastic has the following advantages among other materials:

  • light weight, which reduces the load on the load-bearing parts of the roof;
  • ease of installation and processing with tools;
  • resistance to temperature changes and certain mechanical loads;
  • low thermal conductivity due to high air content - 98 percent;
  • long service life;
  • maintaining properties and shape while high humidity, he is not afraid of mold and mildew;
  • affordable cost;
  • environmental friendliness;
  • fire safety (foam plastic can only melt and not ignite);
  • hypoallergenic.


Of course, foam plastic also has disadvantages:

  • if the material is exposed to open fire, it emits harmful substances;
  • is able to absorb moisture, albeit in small quantities, which is why rafters, sheathing, finishing materials become covered with mold and mildew, and metal fasteners become covered with rust;
  • it is impossible to completely position the foam between the rafters, as it is too rigid; in this case, condensation and cold bridges form;
  • has low breathability;
  • polystyrene foam can be chewed through and colonized by rodents (extruded polystyrene foam is an exception);
  • Solvents, alcohols, gasoline are dangerous for him;
  • destroyed by exposure to ultraviolet radiation.

Attention! Despite the fact that high fire resistance is one of the advantages of polystyrene foam (it does not spontaneously ignite), if the material burns, toxic substances are released. That is why the installation of polystyrene foam must be accompanied by compliance with all fire safety rules.


Standard Sheet foam plastic can be following sizes(mm):

  • 500×1000;
  • 1000×1000;
  • 2000×1000.

The thickness of the insulation varies from 10 to 100 mm. The number contained in the insulation marking indicates the density (kg/m3). For internal or external roof insulation, polystyrene foam of the PSB-15 or PSB-S-25 brands is usually used.

Having studied the characteristics of foam plastic and comparing them with other materials for thermal insulation, each builder himself decides whether to use this material for insulation or replace it with another.

Do-it-yourself roof insulation with polystyrene foam


Before work you should prepare:

  • material that will be used for waterproofing;
  • polystyrene foam of the selected type (taking into account the required thickness and size);
  • vapor barrier film or membrane;
  • self-adhesive tape to glue the joints and overlaps of steam and waterproofing materials;
  • polyurethane foam;
  • construction stapler;
  • scissors and knife;
  • wooden blocks;
  • hammer;
  • material that will be used for final finishing in places of insulation.


After preparing the necessary materials and tools, you can begin to insulate the roof using polystyrene foam.

This happens in the following order:

How to insulate a roof with foam plastic from the outside?


Foam boards Flat roofs are often insulated from the outside. To do this, the roof is well cleaned and covered with waterproofing. Polystyrene boards can be laid as flooring, glued, or secured with dowels. An important condition is to lay the slabs as tightly as possible so that gaps do not form.

The vapor barrier membrane can be laid at the bottom of the heat insulator, placing it on concrete base, then begin the installation of polystyrene foam slabs, cover them with expanded clay, on which a cement-sand reinforced screed is laid. Also, using polystyrene foam, you can create a roofing “pie” consisting of:

  • reinforced concrete base;
  • bitumen-polymer waterproofing;
  • slab heat insulator;
  • geotextiles;
  • gravel backfill.

This combination creates a serviceable roof that cannot be destroyed. high loads.


External thermal insulation technology:


This option is the most common method of attaching material to the surface of concrete slabs. This method is suitable for insulating a flat roof. Moreover, you can insulate both a new roof and a restored one.

Conclusion

Regardless of the choice of insulation by the master, the so-called protective “pie” always includes foam plastic and waterproofing. Careful adherence to the required rules during installation will allow you to live in any home comfortably and without additional heating costs.

Video on roof insulation with foam plastic

The installation of the roof is an important stage in the construction of a building, because heat escapes from the living space through it. From the right decision The comfort in the house depends. TO modern means Leak prevention includes polystyrene foam. It is based on small fragments of expanded polystyrene, saturated with air - a natural heat insulator.

The insulation is produced in various designs, which allows you to select them for each specific case. Dense blocks can withstand high pressure and are laid on top. Thanks to these properties, you can walk on them without protective flooring. For attic roofing, less dense sheets of low cost are required. The master’s decision to use certain modifications of the product depends on the purpose of the upper floor, wishes for the temperature in this room, and the composition of the insulating shell.

The material comes on sale in the form of rectangular slabs of various sizes. To quickly distinguish it from similar products, the PS or PSB marking with an alphanumeric designation is used. For example, model PSB-S-15 refers to self-extinguishing foam with a density of 15 kg/m 3.

The technology of work depends on the type of roof. The roof of the attic is protected from below. Flat structures are covered with material on the outside.

When insulating the roof, pay attention to the following points:

  • Sealing the gaps between the sheets is important. Cold bridges may appear in these places, which worsen the thermal insulation of the house. Also, through poorly closed joints, water enters the room and causes rotting of beams and slats.
  • Experts do not recommend using conventional plastic film for roof waterproofing. Very quickly it breaks down and ceases to perform its functions.

Advantages and disadvantages of roof insulation with foam plastic


The foam-based protective shell compares favorably with coatings for similar purposes:
  1. The light weight and precise dimensions of the slabs speed up installation work.
  2. It is safe to insulate dilapidated buildings that cannot support heavy weight.
  3. The material practically does not absorb moisture and does not deform after getting wet. It does not need to be protected from water by waterproofing, provided that the joints between the slabs are sealed. The product has proven itself well on the roofs of houses in damp areas. After getting wet, it retains its beneficial qualities.
  4. The sheets do not change their size with temperature fluctuations. This property is especially valuable for roofing, which operates in different conditions in winter and summer.
  5. The insulation does not shrink over time.
  6. Retains its properties throughout the life of the building.
  7. Easily cut to obtain samples of required sizes.
But not everything is so good with foam coating:
  • It becomes a refuge for mice, which quickly destroy it.
  • It takes a lot of time to insulate a house that has been in use for a long time due to the presence of lathing. In this case, you have to cut the blanks in place.
  • In the absence of good ventilation, mold appears on the surface.
  • The foam roof does not match modern ones. fire safety standards. The material melts under the influence of high temperature, and in the event of a fire it begins to burn.
  • At high temperature, which happens in the summer, the roof gets very hot and the heat insulator releases fumes that are harmful to humans.
  • Sun rays are harmful to the product and quickly damage it. Therefore, it is necessary to have a protective layer over the insulating layer.

Materials and tools for roof insulation


It is necessary to cover the roof only with high-quality foam plastic.

In the store you can perform simple operations that will help you get an idea of ​​the condition of the insulation:

  1. Study the structure of the panels. The presence of fragments of the same size, which are evenly located in the slab, indicates a quality product. The granules must be small; large particles cause the formation of voids and saturation of the insulator with water.
  2. Foam plastic is always white. A change in shade indicates the use of low-quality components for its production.
  3. Check the storage conditions of the products. It is usually sold in batches of 10, wrapped in plastic wrap. Refuse goods with torn packaging. Sometimes it is sold individually, with characteristics applied to the surface at the factory.
  4. Carefully study the label, which should contain information about the manufacturing company, slab sizes, product characteristics, etc.
  5. The blocks are manufactured with great precision. Deviations in size, especially in thickness, should alert you.
  6. Foam sheets do not smell at all.
  7. Make sure the sheets are pliable and not hard. After pressing with your finger, the surface will be slightly deformed, and then the shape will return. Solid products become due to technology violations. Such samples do not do their job well.
  8. Find the broken slab and inspect the damaged area. The broken granules should be visible on the fracture. If the fragments remain intact, you have a fake in your hands.
  9. Weigh the mass of 1 cu. meters of goods. It must weigh at least 15 kg.
The following information can help with your choice:
  • The thickness of the sheets can be accurately determined based on the requirements of SNiPs, but it must be at least 100 mm. The size is influenced climate zone, roof material and its design. For areas with mild winters, the approximate coating thickness is 150 mm, for harsh conditions - 200 mm.
  • High-quality insulation is produced by the following companies: Knauf, Penoplex, Stav Polister, T-life.
  • The scope of application of a product can be determined by its labeling. For attic roofing, PSB-S-15 foam with a density of 15 kg / m 3 is best suited. More rigid products PSB-S-25, PSB-S-35 can also be used, but they are more expensive. These modifications differ from other models in their self-extinguishing properties, which are characteristic of materials for internal use.
You can glue foam plastic to a flat roof using two types of compounds: universal and special.

They all must meet the same requirements:

  1. The products are intended for external use (for flat design) or inside (for attic roofs).
  2. Interior work perform with compounds with a minimum degree of toxicity. Thus, in a room closed on all sides, a person will not feel discomfort. The degree of toxicity is always included by the manufacturer in the certificate of conformity.
  3. The substance retains its basic characteristics at any ambient temperature, throughout the entire service life of the insulation.
  4. The glue does not harm the insulator. It does not contain gasoline, kerosene, solvents or other components capable of dissolving foam.
  5. Adhesive mixtures are hygroscopic, so they must be stored under appropriate conditions.
  6. Give preference to products that do not harden instantly. This will make it possible to move the slabs along the surface to adjust their position during installation.
  7. The product must not be past its expiration date. For this reason, refuse glue that the store offers on promotions. Usually it can no longer be used.
  8. Ask the seller to present a quality certificate.
  9. Use products from a reputable manufacturer. If the company is unknown, look for reviews about it on the Internet.
  10. Buy funds with a reserve. IN reference information The label indicates the average consumption, but on a non-flat surface the number of packages of the substance used will be greater.
  11. The most convenient is foam adhesive, which is sold in cans ready for use. The disadvantage is the high price.
When installing blocks, small samples or non-standard shaped panels are always needed. To make the task easier, craftsmen use simple devices:
  • All kinds of sharpened knives - kitchen, wallpaper, stationery. The work is accelerated if the blade is held over the fire.
  • An electric jigsaw has proven itself well when processing thick workpieces. Negative side use of the tool - poor cut quality.
  • Heated nichrome wire quickly cuts off a curved section with straight ends.

Insulating the roof from the inside with foam plastic


When insulating the roof from the inside with polystyrene foam, the panels are laid between the rafters. The high density of the sheets allows them to be fastened to the frame using improvised means, which does not increase the load on the structure.

The building can be thermally insulated if the following conditions are met:

  1. The drainage system is installed taking into account the slope of the structure.
  2. The height of the attic roof allows you to close the roof racks from the inside.
  3. After installation, there remains a guaranteed ventilation gap between the waterproofing and the roof cladding.
Installation of the protective shell occurs as follows:
  • Apply to all beams and slats. antiseptics. The work is easier if the outer roof cladding has not yet been installed.
  • Cover the rafters on the street side with waterproofing film and secure them to the beams in any way. The membrane is necessary so that water does not enter the room from outside, and moist air from the insulating “pie” freely escapes outside. Do not pull the panel, leave a slight sag. Lay the cuts with an overlap of 15-20 cm on adjacent pieces and on the walls. Connect the joints with reinforced adhesive tape.
  • If an existing house is being renovated, lay the film from the inside of the attic, while monitoring the gap of 50-60 mm between it and the roofing material.
  • When covering the roof with soft bitumen shingles It is allowed not to lay waterproofing tape, because the cladding itself is waterproof. Only corners and cornices are covered. In case of insulation soft roof The foam membrane is laid directly under the cladding. If the top is made of metal tiles, the composition protective coating Soundproofing elements must be included to muffle the noise from rain.
  • Attach the sheathing to the rafters and install the outer cladding. Make sure that there is a ventilation gap of 50-60 mm under it to the film, which is necessary to remove moisture. Through it, the moisture remaining in the roofing “pie” is evaporated. To organize air flow, special holes are made in the eaves and upper part of the roof. You can also forcefully ventilate the space using special devices.
  • Measure the distances between the rafters, add 0.5 cm and cut the blocks from the blanks. Increasing the size will allow the panels to self-adhere between the beams, making installation easier.
  • Place the panels in a position that leaves a gap of 10-15 mm between them and the outer film. It is necessary so that the insulation does not close the pores of the diaphragm.
  • To ensure the required thickness of the coating, the panels can be laid in two rows, with the lower one covering the joints of the upper one.
  • The method of fastening depends on the roof structure. You can fix the products in this position with thin slats or special corners, which are sold in the store. Manufacturers also allow gluing and mechanical fixation using dowels with wide hat, anchors, etc. Options can be combined.
  • Seal the gaps between the panels, as well as near the rafters, with scraps. Allowed to eliminate defects polyurethane foam.
  • Cover the beams from the attic side with waterproofing film and secure them to the battens with a construction stapler. The canvas should sag slightly. The membrane will prevent the rafters from getting wet from moist air rising from the lower rooms. Lay the pieces of canvas overlapping each other and on the walls. Seal the joints with reinforced adhesive tape. If desired, you can trim the rafters with boards.
  • For vapor barrier, it is advisable to use a special three-layer membrane reinforced with a polymer frame. Modifications with foil coating have also proven themselves well.

External roof protection with foam plastic


This is the most common option for attaching material to concrete slabs. Typically, this method is used to insulate a flat roof with polystyrene foam facing outwards. Applicable as per new roof, and on the restored one.

The order of operations is as follows:

  1. Clean the ceiling from dirt and deposits.
  2. Inspect the slabs for cracks, fill them with cement-sand mortar. Knock down any protruding parts.
  3. Fill the surface with a cement-sand screed 15-20 mm thick, ensuring the roof slope is within 5 degrees.
  4. Check the flatness of the roof with a long ruler. After applying the tool to the surface, there should be no gaps left underneath it.
  5. Treat the screed with a deep penetration primer. Foam plastic does not absorb moisture, so if glued, the waterproofing film on the room side does not need to be laid.
  6. If desired, the screed can be coated with bitumen mastic.
  7. Spread the entire sheets with a 10 mm thick layer of glue, making sure that there are no untreated areas left. Do not lubricate the ends.
  8. Run a notched trowel over the surface.
  9. Place the panel on the ceiling and press down lightly.
  10. Repeat the operation for all slabs. When installing, press them tightly against each other.
  11. Place the products so that there is no single joint line. Fill the resulting gaps tightly with scraps of material. Use non-standard panels last.
  12. When laid in two rows top layer position it so that it overlaps the joints of the lower one. Glue the panels together by special means, which are intended for foam plastic.
  13. Cover the insulation with geotextile - a super-dense fabric made of a special material that protects the product from ultraviolet radiation. It also distributes the load on the base when walking. The material is almost impermeable to water.
  14. Fill the area with gravel of the 16-32 mm fraction in a layer of no more than 5 cm. Another option is to put concrete screed 5-6 cm thick, but this method will require additional costs for cement. Solid protection allows you to cover the insulation with additional waterproofing. The most popular option is roofing felt. It significantly increases the service life of the entire layer.
How to insulate a roof with foam plastic - watch the video:


Whatever insulation option the master chooses, the protective “pie” will always consist of foam plastic and waterproofing. Compliance with the installation technology requirements will ensure living comfort and reduce heating costs.

The question: is it possible to insulate a roof with foam plastic, perhaps, is as pressing as the phrase “Execution cannot be pardoned.” In fact, there are diametrically different opinions on this topic online. Let's devote one more material to the burning issue that arises when it is necessary to insulate a roof. Should I use polystyrene foam for the roof, or maybe choose a proven option that no one disputes?

Well, firstly, when a user enters the query: roof insulation with polystyrene foam, it is not at all clear what kind of roof he has. Attic or cold attic, or maybe we are talking about flat roof insulation? The type of roof is the first question that needs to be clarified.

In order not to languish with long expectations, it is worth saying that we have already discussed the issue separately. The issue of a flat roof will be discussed later, in a nutshell: it is insulated, most often with penoplex or expanded polystyrene. That is, it is quite possible. Although in most cases such roofs are part of industrial buildings and the insulation is carried out by contractor teams.

What can we say about cold roof- the most popular option in domestic conditions?

Features of foam plastic in connection with roofing

It is worth noting that there are different types expanded polystyrene, each of which is applicable for its own purposes.

  • Ordinary polystyrene foam (marking PSB 15) is the most common, white foam plastic;
  • EPPS - extruded polystyrene foam. A denser, tougher material that can withstand heavy loads. In addition, the latter has lower hydrophobic properties.

And if there are no loads on the roof (if we are talking about insulation between the rafters), then the extra hydrophobicity definitely won’t hurt. You can often find polystyrene foam with a quarter. (Protrusion or groove on the edge).

This material is intended for laying joint-to-joint on flat surface. For example, penoplex is one of these. For use between the rafters, you need even sheets in the form of rectangles.

Why do disputes arise?

There are 5 main questions that arise when it comes to roof insulation with foam plastic. Namely:

  • Need for ventilation wooden structures roofs;
  • Changing geometry truss structures, depending on humidity;
  • Question about vapor permeability of polystyrene foam;
  • Fire safety;
  • Harmful substances when heated under the roof.

Before considering whether these objections are really justified and whether it is possible to overcome them, let us generally compare, and Are there any special reasons that encourage the use of this particular material for the roof from the inside?

To know means to compare

It seems that the most important competitor, by the way, ahead of foam in the field of roof insulation, is mineral wool. Specific solutions, such as ecowool or polyurethane foam, are also used, but their share is lower. In addition, both require special equipment, so it is fairer to compare polystyrene foam with mineral wool in terms of roof insulation.

So, the first indicator for insulation is . How are our friends doing with this indicator?

Thermal conductivity

As you can see in the diagram below, mineral wool is slightly inferior in this regard to its “white” comrade.


For example, to replace a 20 mm thick layer of polystyrene foam, a 40 mm layer of mineral wool is needed. This means that a smaller layer of foam is sufficient to achieve the same effect. What can we say about the cost?

Price

So, for example, 7 sheets of EPS, URSA, 50 mm thick (size 1250 by 600 mm) cost 1,300 rubles (22 dollars). Polystyrene foam, for example, Knauf 50 mm (1000 by 600 mm) will cost 860 rubles ($15).

As we found out, for the same purpose we need 100 mm of wool. For example, let's take the famous Rockwool Light Butts. 5 slabs 100 mm thick cost 580 rubles. The size of one slab is 1000 by 600 mm. Now we need to compare the cost of 1 square meter of such thermal insulation.

The EPS packaging, which costs 1,300 rubles, contained 5.25 m2. The package of polystyrene foam at the price of 860 rubles contained 6 m2. The pack contains 3 m2 of cotton wool. You can take a calculator and calculate or look at the table below.

So, we can conclude that only foam plastic wins in terms of cost. EPS will be much more expensive. Some will appeal to the longer lifespan of polystyrene over mineral wool, but in conditions of use on the roof, it seems that none of the materials will last 50 years.

By the way, specific figures for the thermal conductivity of the materials compared.

As you can see, although there is a gain, it is small.

So, according to two main indicators for materials:

  • Thermal conductivity;
  • price,

The leadership of polystyrene is very doubtful. Are there any questions that definitely need to be taken into account?

Things to think about

Let's return to the 5 points-questions at the beginning of the article:

In general, as you can see, there is something to think about. If, of course, everything is done correctly, namely:

  • Provide sufficient ventilation for the cold roof;
  • Select polystyrene foam of flammable group No. 1;
  • Use chamber-dried timber for rafters,

roof insulation with foam plastic from the inside is possible, provided that the attic will not be residential. However, there are more questions than answers here. But, if for some objective reasons you decided to use this particular heat insulator, below are the installation recommendations.

Let’s make a reservation, if by roof insulation you mean ceiling insulation (from the cold roof), we discussed this issue in a separate article.

Installation of polystyrene foam between rafters

Sheets of foam plastic are inserted between the rafters into a spacer. To achieve the result, you should adhere to the following sequence:

  • Measure the distance between the rafters;
  • Cut a sheet of polystyrene foam to the desired width;
  • Insert the sheet into the sheathing.

Sometimes the width of the rafters does not allow the required thickness of insulation to be accommodated. Considering that there should be a distance of 50-100 mm between the thermal insulation and the hydraulic barrier on top, for example, the thickness of the rafters is 180 mm, only enough to attach 80 mm of foam. The remaining thickness is filled on top, securing the second layer of insulation with self-tapping screws.

The joints between the rafters, if any, are sealed with foam or sealant.

So, today we have such a scandalous topic: how to insulate a roof with polystyrene foam. What do you think about this method of roof insulation?

Finally, 2 videos with polarity of opinions.

Roof insulation is an important stage of construction own home. This work must be carried out efficiently and conscientiously. This determines how warm and dry the house will be, when outside the window it will be damp, cold and uncomfortable.

Modern construction supermarkets and markets offer a huge variety of various materials for roof insulation: mineral wool, fiberglass, basalt slabs, polyurethane foam and a host of other materials. But the invariably leading position is still occupied by polystyrene foam, or, as it is popularly called in the old fashioned way, polystyrene foam in slabs. The most suitable brand for roof thermal insulation is PSB-S-25 and PSB-S-35.

What's good about this material? First of all, due to its rather low cost, as well as excellent performance characteristics.

  • Durability: material is different increased level resistance to compression and tension.
  • Small specific gravity allows it to be used to insulate even dilapidated structures that cannot withstand the mass of other heavier materials.
  • Wear resistance: the material perfectly resists temperature changes, is resistant to mechanical damage and abrasion.
  • Moisture resistance: foam plastic does not absorb moisture at all, therefore, the material is not subject to deformation under its influence.
  • Fire resistance: the material is not prone to spontaneous combustion. It is best to choose material from group G1 for roof insulation.
  • Ease of installation: work on roof insulation with foam plastic can be done even by an inexperienced person.
  • Durability of the material: the service life of such insulation is from 25 to 80 years.

Relatively recently, liquid foam appeared on the shelves. This material has the same characteristics as foam plastic in slabs, but is radically different in the method of application: penoizol is sprayed over the surface using a special installation. Thus, a seamless continuous layer of thermal insulation is formed on the surface. The only negative this method is the need for additional fixation of the surface by installing thin sheets of ordinary polystyrene foam or drywall.

Determining the amount of material

Before starting work on insulating the roof with foam plastic from the inside, you need to calculate the amount required material. For insulation mansard roof calculating the optimal amount is not difficult - you just need to measure the roof area, the pitch between the rafters and determine the size of the foam boards. However, experts recommend purchasing material with a small reserve (6-8 slabs), since in the process of cutting it there may be a risk of deformation or breakage of the slab.

Insulating an attic roof with foam plastic - tools and materials

To work you will need the following materials and tools:

  • foam;
  • anti-condensation vapor barrier film;
  • wooden blocks;
  • nails;
  • scissors;
  • sharp knife;
  • polyurethane foam;
  • construction stapler.

The final result depends entirely on how well and conscientiously the main stages of the work are completed.

Roof insulation - based stages:

  • preparatory;
  • flooring waterproofing and vapor barrier film;
  • installation of insulation;
  • interior decoration.

Surface preparation, waterproofing and vapor barrier

The surface on which the foam will be laid must be clean and dry.

Expanded polystyrene does an excellent job of waterproofing. But in order to extend the service life of foam plastic, a vapor barrier must be installed.

Please note: it is imperative to leave a gap of at least 2 cm between the film and the sheathing. If you do not do this, condensation will constantly accumulate on the inside of the insulation, which can lead to the process of rotting of the rafters, the appearance of unpleasant odor, mold, etc.

In some cases, an anti-condensation vapor barrier film is laid: overlapping directly onto the rafters. This is done in cases where the width of the rafters does not allow leaving a gap between the polystyrene foam and the plank base. If we are talking about a ready-made building, the option of attaching this anti-condensation film to the rafters using wooden slats and nails. It is also quite possible to use a special construction stapler for these purposes.

Installation of insulation

The most common methods of fastening polystyrene foam boards:

  • gluing (frost-resistant facade adhesives, liquid nails, mastics for gluing tiles to the ceiling, instant installation);
  • mechanical fastening (umbrella nails, anchors, wooden slats);
  • flooring;
  • investment in sheathing.

Sometimes fastening methods are combined. So, polystyrene foam is placed into the sheathing, and additionally secured with umbrella nails. This fastener is also called a dowel for foam plastic with a thermal head.

Often they combine gluing foam and fastening it with screws. You can glue polystyrene foam onto brick, drywall, plywood, concrete, and iron.

Polystyrene foam on the attic roof

After arranging the vapor barrier layer, it’s time to start installing the insulation - foam sheets. Traditionally, the attic roof is made on a rafter frame; foam plastic slabs should be placed between these rafters. In the process of selecting such, preference should be given to slabs whose size is equal to the width of the step between the rafters. But modern materials allow you to insulate roofs with a pitch width of up to 2 m without gaps.

Foam insulation boards should be placed between the rafters along the sheathing or on top of them. In order for the insulation to hold more firmly and reliably, experts recommend using glue and dowels at the same time. During operation, gaps and cracks may form between the rafters and foam boards. They must be carefully sealed using ordinary polyurethane foam (it is quite possible to use any type of sealant).

After all these steps you can perform exterior finishing surfaces - in case you plan to arrange attic room. The best option The least labor and financial cost is to finish the surface with plasterboard sheets, which are attached to the rafters using dowels. Next, it is quite possible to paint the surface or cover it with wallpaper.

Polystyrene foam on a flat roof

A fairly common method of insulating flat roofs with polystyrene foam. The surface is cleaned and covered with a waterproofing film. Expanded polystyrene can be laid on flat roof free, hot and cold fastening, nailing.

It is important to lay the slabs close to each other.

Expanded polystyrene is often involved in creating the roofing “pie”:

Option 1

If polystyrene foam is laid on a flat roof, then it is combined with geotextiles, after which a layer of gravel of fraction 16/32 with a thickness of at least 5 cm is poured. This type of roofing is increasingly used in modern urban planning. This makes it possible to arrange a recreation area, lawns and even parking lots on the roof.

Option 2

Option 3

The third option for insulating the cake: vapor barrier, polystyrene foam boards, a layer of expanded clay, reinforced cement-sand screed 30-40 cm thick.

The use of the technologies described above makes it possible to equip such oases on the roofs of houses. This is called inversion roofing. For its arrangement, polystyrene foam is material No. 1.

How to insulate a roof with foam plastic and avoid common mistakes?

Installation of insulation done incorrectly will make itself felt in the near future. unpleasant consequences. Leaks that form as a result of poorly performed work will not only disrupt the aesthetic picture, but will also contribute to the process of rotting of the rafters.

Let's look at the main ones possible errors, most often allowed during the installation process:

  • the formation of depressions and cavities on the surface of the insulation. This can lead to the formation of cold bridges. During the installation of insulation, the appearance of such defects must be avoided;
  • incorrectly chosen width of the insulation board also leads to a violation of the tightness with all the ensuing consequences;
  • Using cellophane film instead of anti-condensation vapor barrier is perhaps the most common mistake that can cause many troubles and troubles.

To ensure that your home is always warm, dry and comfortable, you should not neglect the rules and standards during the installation of insulation. All work must be performed strictly in accordance with generally accepted canons. Also special attention It is necessary to pay attention to the quality of the materials used.

Many owners of private houses are wondering whether it is possible to insulate the roof with foam plastic. It's possible, of course. The material does not harm health, and also has excellent performance characteristics and a fairly reasonable cost. But it is sensitive to resins and oil paints, must be operated at -50...+75 degrees, its installation provides for the presence of gaps that need to be additionally processed.

Comparing polystyrene foam with other types of insulation (mineral wool, penoizol, polyurethane foam), we can definitely say that polystyrene foam is best insulation for the roof, no. But in some cases it is simply irreplaceable, and one of them is the installation of an inversion roof.

Installation of roof insulation is one of the important stages construction of a country house.

Measurements and calculations show that, on average, through a roof laid without thermal insulation, up to 30% of heat is lost.

You can block the path to these losses with the help of various thermal insulation materials. However more often than others modifications of it are now used.

Insulation with polystyrene foam pitched and flat roofs and ceilings.

The popularity of this material is quite understandable: it is light and easily processed, has very low thermal conductivity, is not spoiled by microorganisms and not afraid of water.

However he has some features, which affect the installation and installation sequence, as well as the operation of the house:

  1. Vapor tightness. Polystyrene foam and other modifications of polystyrene foam allow only a few milligrams of water vapor per hour to pass through 1 square meter surfaces. They also do not allow water to penetrate deep into the material, but due to their porous structure they can collect some moisture on the surface. At the point of contact with wooden structures, this leads to rotting of the wood, and the foam itself turns black on the surface. For this reason, all modifications of polystyrene foam must be protected with vapor and waterproofing films, and the room must be ventilated. Subject to such conditions, this material lasts up to 80 years or more.
  2. Flammability. Modern foam plastic of the PSB-S brand is a self-extinguishing material. This means that it lights up, but after the flame is removed it goes out. However, it is a flammable material, so it should not be installed around the chimney. In this place, mineral wool and expanded clay are used for thermal insulation.
  3. Low elasticity. Unlike mineral wool Expanded polystyrene has almost no elasticity. For this reason, slabs are cut out of it, which are only 1 cm wider in width than the distance between the rafters. Such slabs fit tightly into the opening. If you increase the width of the slab, it will warp during installation. This leads to the formation of gaps between the plates and the formation of cold bridges. The edges of the slabs do not fit tightly to the wood everywhere, so the cracks have to be filled with foam.
  4. Sensitivity to sunlight. Expanded polystyrene of all modifications is destroyed ultraviolet rays sunlight. This means that when laying it, it is carefully protected from light rays. The outer side is covered with roofing material, and the inner side is covered with a vapor barrier membrane and finishing. Leave the foam even with inside You can't do it without finishing. Light coming through dormer windows, causes yellowing and destruction of this material.

Choosing tools and materials

Polystyrene foam is available in various modifications, whose properties will have to be taken into account when choosing materials (according to GOST 15588-86 and SP-50.13330.2012).

The best thermal insulation properties have polystyrene foam brand PSB-S-35 and extruded polystyrene foam (penoplex). They also withstand significant compressive loads.

All of the above brands are suitable for roof insulation, but usually used PSB-S-15, because it creates minimal load on attic floor. PSB-S-35 and (), as a rule, are used for insulating flat roofs, since resistance to compression is required there.

For work you will also need:

  1. . It will protect the insulation and rafters from steam penetration from the room. It is recommended to choose a two-layer water vapor barrier membrane Megaspan B. Its rough side holds drops of condensation on its fibers, preventing it from draining. After the air humidity decreases, the condensate evaporates.
  2. Windproof, moisture-proofing membrane. This membrane protects the insulation from drops from above when the roof leaks, but allows steam to pass through, which is formed when wooden structures dry out. It is advisable to choose a membrane type Megaspan A or other superpermeable membranes.
  3. Wooden blocks with a cross section of 50×50 or 40×50 mm, treated with antiseptic preparations. They are needed to construct the sheathing.
  4. Nails and hammer for attaching film and finishing material.
  5. A sharp knife for cutting foam.
  6. Polyurethane foam without toluene for sealing joints.
  7. Stapler and staples for attaching film.
  8. Construction tape.

Technology for insulating a gable roof with foam plastic from the inside

It is advisable to install thermal insulation under the roof immediately when installing the roofing material. However, the developer does not always manage to do this. In such cases, insulate the roof comes from within.

Modern installation technology roofs require the installation of a wind and moisture protective membrane. If it has been laid in compliance with all the rules, you can immediately begin installing the insulation.

Polystyrene foam is cut into slabs of width 1 cm larger than the distance between the rafters so that they fit tightly into the opening.

The slabs are laid in several layers, overlapping the joints of the previous layer with the slabs of the next one. It is recommended to glue polyurethane foam one layer to another and fill all the resulting gaps between them and the rafters so that cold bridges do not form.

After filling the openings Between the rafters, a vapor barrier membrane is stapled to their lower surface. Instead of fastening with brackets, the film can be fixed with wooden strips, through which the film is nailed to the rafters. It is unfolded and laid from bottom to top, overlapping the edges of the bottom layer by 15 cm.

The joints of the canvases are taped with tape. A double-sided membrane of the Megaspan B type is always laid with the smooth side facing the foam. After installing the vapor barrier a sheathing is constructed on the rafters, to which it is attached finishing material. After completing this stage, an air ventilation layer is formed between the film and the finish.

If the roof has been laid without waterproofing membrane, work will have to begin with its installation. In this case, the membrane is laid around the rafters with the pile facing the insulation. They attach it to the rafters and external sheathing. Only after the membrane is secured, do you begin laying the insulation.

Features of flat roof insulation

This can be done immediately after installation of the ceiling. Usually such an overlap is used reinforced concrete slabs , which need to be cleaned and a vapor barrier membrane attached to them.

For thermal insulation of flat roofs, foam plastic that can withstand pressure well is chosen (see above). Sheets of this insulation are glued onto film and secured to reinforced concrete with dowels. Laying rule the same: each subsequent layer must overlap the joints of the previous slabs.

The foam is covered with fiberglass on top, and then with a waterproofing membrane, on top of which lay geotextiles. Geotextiles can be covered with expanded clay, onto which a reinforced cement-sand screed is poured, and then paving slabs are laid.

If it is difficult to install external thermal insulation for some reason, a flat roof can be insulated with foam plastic from below. If roof covering reliably, then the shift of the dew point towards the room does not matter. First, a sheathing of wooden blocks is mounted on the floor slab, securing them in the slab with dowels.

Expanded polystyrene boards glue directly to a clean and dry floor slab between the bars, and then additionally secure with dowels. The joints are also sealed with polyurethane foam.

The insulation is insulated from the steam from below with a vapor barrier membrane with the pile facing down. It is nailed to the bars with nails through wooden planks. Next, the insulation is hidden behind a suspended or suspended ceiling.

Thermal insulation of a roof with foam plastic is simple and does not require high qualifications. After studying the properties of materials and mastering the skills of working with them, any home handyman can handle this kind of work.

Foam insulation requires thorough hydro- and vapor barrier, as well as protecting this material from sunlight.

Watch the video for a master class on roof insulation with foam plastic: