Roof insulation with mineral wool: secrets and subtleties of technology

Roof insulation with modern heat-insulating materials is not only a hidden resource for reducing energy costs for heating a house, but also a good opportunity to get an additional room at your disposal for year-round living. One of the best ways to protect an attic space from the cold is thermal insulation with mineral wool. Today we will consider the features of this material, tell you which insulation is better and how much it will be required. And most importantly, we will reveal all the secrets of the technology and share with you the recommendations of experienced specialists.

What is good about mineral wool: features and characteristics of the material

A clear definition of thermal insulation materials such as mineral wool is given by GOST 52953-2008, according to which this class of insulation includes:

  • glass fiber;
  • slag;
  • stone (basalt) wool.

All three types of heat insulators are suitable for use in private construction. And although they are based on a similar synthetic fiber structure, each insulation has its own advantages and disadvantages. For this reason, we will consider their characteristics separately.

Different types of mineral wool have a similar structure, but this material is one of the best insulation for walls and roofs of the attic or attic.

Glass wool

The composition of glass wool includes many threads, which are obtained by hot drawing from broken glass or quartz sand. And although such fibers have a diameter of only 5-15 microns, it is they who make the cotton insulation strong and resilient. The main characteristics of glass wool are:

  • fiber length from 15 to 50 mm;
  • thermal conductivity in the range of 0.038–0.046 W / (m · K);
  • permissible temperature range from -60 to +450 ° С;
  • hygroscopicity per day is not more than 1.7% of the mass.

Being a chemically inert substance not susceptible to bacterial attack, glass wool has one significant drawback. The fact is that extremely strong and thin fibers, upon contact, can dig into the skin and enter the human respiratory organs. This is fraught with painful irritation of the skin, allergic reactions and even asthma attacks in people who suffer from asthma. For this reason, it is better to refrain from using glass wool in a residential area.

Glass wool fibers are the thinnest needles that can harm the skin and respiratory organs


Slag wool is made from blast-furnace by-products and has the same disadvantages as glass fiber. However, it is not recommended to use it for the insulation of residential buildings for a completely different reason. The fact is that blast-furnace slags, from which thermal insulation is made, can be dangerous for reasons of environmental friendliness, including radioactive radiation. Slag wool is the most hygroscopic in its class and, when saturated with moisture, loses a significant part of its thermal insulation capacity.

If you nevertheless decide to insulate any utility room with slag, we suggest that you familiarize yourself with its technical characteristics:

  • thermal insulation capacity of dry material - 0.46–0.48 W / (m · K);
  • maximum operating temperature - no more than 300 ° С. Exceeding this indicator leads to sintering of the fibers, after which there is a sharp increase in thermal conductivity;
  • hygroscopicity - 1.9% in 24 hours.
It should be clarified that it is possible to insulate metal structures with slag wool only in completely dry rooms. The author of these lines had the imprudence to use such thermal insulation to protect the garage doors from freezing, and for a long time could not understand the reason for such a rapid corrosion of the metal sheet cladding. As always, the reason lay on the surface. The fact is that blast-furnace slags have a high acidity - this is it, and even multiplied by the dampness emanating from the inspection pit, and became the cause of rust and rapid destruction of the metal.

Due to the low environmental safety, slag wool can only be used as a budget insulation of external walls.

Stone wool

Being the same synthetic material as the heaters discussed above, stone wool has several undeniable advantages. Although its threads are similar in size to cinder fibers, they have a significant advantage, since they do not prick at all. Therefore, it is much safer to install stone wool than to work with glass and slag fiber insulation.

Stone wool is often called basalt, since gabbro-basalt rocks are used for its production. Nevertheless, these two types of thermal insulation should be distinguished. The fact is that the latter is made without the use of synthetic binders and therefore is safer.

Stone wool characteristics:

  • thermal conductivity coefficient in the range of 0.035–0.042 W / (m · K);
  • maximum operating temperature - up to 1000 ° С;
  • hygroscopicity - no more than 0.95% in 24 hours.

It is easy to see that among the wadded fibrous insulation there is no material with the same low hygroscopicity as stone wool. By the way, its wide popularity has led to the fact that the concept of "mineral wool" most often means this particular material.

In the production of stone wool, a mineral base is used - basalt, gabbro or diabase, as well as a small part of blast furnace slag, charge, clay and other natural binders. It is due to the latter that the level of harmful formaldehyde resins decreases. As for basalt insulation, it is made from natural materials and therefore has maximum environmental friendliness.

Demand creates supply, which is why today stone wool is the most popular thermal insulation material.

For insulation of horizontal and inclined roof surfaces, it is best to use mineral wool with a density of 25 to 75 kg / m3 - this will allow not to exceed the permissible load on the rafter system. To find out the density of thermal insulation, just look at its brand. For example, P-25 is a material with a density of 25 kg / m3.

Advantages of mineral wool:

  • relatively low hygroscopicity allows the use of insulation for both indoor and outdoor installation;
  • the porous structure provides good sound and heat insulation;
  • resistance to ignition and combustion;
  • minimal shrinkage;
  • high resistance to critical temperatures;
  • environmental Safety;
  • ease of installation - the material is produced in rolls and slabs of various sizes and thicknesses;
  • resistance to biological and chemical factors.

Of course, there were some drawbacks. Although stone wool does not prick, the increased fragility of its fibers leads to dust formation - the smallest particles rise into the air and, when inhaled, enter the lungs and eyes. Therefore, during installation, it is imperative to use a respirator and goggles.

Despite the environmental safety of basalt wool, it is not recommended to work with it without a respirator and glasses.

Another significant drawback is that when stone wool is heated above the permissible values, it begins to release phenol, which is harmful to health. For this reason, in places that are exposed to high temperatures, it is best to use the more expensive basalt insulation.

Why do you need an accurate calculation of the thickness of the insulation and how to make it

Installation of mineral wool without accurately calculating the thickness of the insulation is one of the most common mistakes novice builders make. More often than not, newbies act on the principle "the more the better." However, this approach is not only wrong, but in some situations and harmful.

At best, the extra spending will be useless. In the worst case, due to a too thick layer, the ventilation of the middle layers of the insulation will stop, due to which moisture will accumulate inside the thermal insulation cake. If the thickness of the mineral wool turns out to be insufficient, then in addition to unjustified heating costs, the dew point will shift into the thickness of the insulation or onto the walls of the attic floor. There is probably no need to say that the formation of condensation causes the appearance of mold and mildew.

It is possible to reduce heat costs only if the thickness of the thermal insulation exceeds 50 mm - otherwise, the insulation will be useless

Accurate calculation of the thickness of the seal is the only correct solution, thanks to which it will be possible to:

  • avoid unnecessary expenses;
  • increase the service life of thermal insulation;
  • create the most comfortable atmosphere in the room;
  • save heat energy.

I must say that calculating the thickness of thermal insulation is a rather trivial task. The first thing to do is to find out the minimum allowable heat transfer resistance R, which the roof should have. The value of this parameter depends on the climatic characteristics of the region and is indicated in the SNiP 23-02-2003 table, some excerpts from which can be found below. For example, for Tyumen R = 5.26 (m2° С) / W.

Table: optimal resistance to heat transfer for different cities of Russia

CityResistance to heat transfer, (m2° С) / WCityResistance to heat transfer, (m2° С) / W
Yekaterinburg5,19St. Petersburg4,6
The physical meaning of such a parameter as resistance to heat transfer is to determine the amount of heat in watts that passes per unit of time through 1 sq. m of heat-insulating pie of the roof with a temperature difference between inside and outside the room of 1 ° C.

Next, we need to find the coefficient of specific thermal conductivity λB of the type of mineral wool that will be used for insulation. This data can be found on the packaging of the thermal insulation, in the data sheet or in the product certificate. In extreme cases, you can see the value of thermal conductivity on the manufacturer's website.

To determine the minimum thickness of thermal insulation δ (m), find the product of R and λБ. For example, if soft basalt wool slabs are used to insulate the roof of a house in the Tyumen region, for which there is no documentation, then a layer of δ = R λB = 5.26 0.036 = 0.189 m = 19 cm is required. Since stone wool is produced in rolls and slabs 5 and 10 cm thick, then the value is rounded to the nearest multiple of 20 cm.

If it is not possible to determine the brand and manufacturer of mineral wool, then you can use the data from the table below.

Table: thermal conductivity of mineral wool of various degrees of density

Mineral wool typeInsulation density, kg / m3Thermal conductivity, W / m ° С
Matsfrom 50 to 850,046
Light slabfrom 30 to 400,036
Soft platefrom 50 to 750,036
Semi-rigid slabfrom 75 to 1250,033
Rigid platefrom 175 to 2250,043
Cylinderup to 2000,046
Loose cotton woolnot less than 300,050

Video: what should be the thickness of the insulation for the roof

Methods for thermal insulation of the roof with mineral wool from the inside of the room

High-quality roof insulation implies not just laying mineral wool on the rafters, but the construction of a multi-layer roofing cake. Of course, it is best to deal with thermal insulation at the stage of building a house, before installing the roofing. Among other things, this allows you to get an attic interior with decorative ceiling beams at no special cost. And nevertheless, it is never too late to make your home more energy efficient or get another full-fledged room. For this, roof insulation is carried out from the inside. And since mineral wool is an extremely simple and easy-to-use material, you can do the installation yourself. Immediately, we note that the expected result can be obtained only if the technology provided by the manufacturers of the material is maintained.

In general, the roof insulation from the side of the attic floor can be divided into several stages:

  • preparatory work;
  • installation of waterproofing;
  • laying insulation;
  • installation of a vapor-tight membrane;
  • fastening decorative cladding.

Preparatory work is an inspection of the wooden frame of the truss system, repair and replacement of damaged elements, as well as the treatment of wood with fire retardants and antiseptics. As for the roofing cake, depending on the design features of the roof, there are several ways to build it.

Video: features of a roofing cake when using mineral wool

Insulation installation technology inside the roof frame

The main advantage of laying mineral wool inside the roof frame is that this method does not take away a single centimeter of free space from the room. To work you will need:

  • mineral wool;
  • diffuse waterproofing;
  • vapor barrier membrane;
  • special tape for gluing joints;
  • nails;
  • synthetic cord or twine;
  • wooden beams or slats.

In addition, you should take care to have a hammer, furniture stapler and a large construction knife on hand.

When cutting slabs of stone wool 50 mm thick with a knife with breakable blades, as a rule, there are no problems - a board can be laid in the place of the cut, which will also serve as a guide. Difficulties begin with cutting the material with a thickness of 100 mm and when making a curly edge - the knife crumples and crumbles the sealant, tearing pieces of cotton wool out of it. In order not to buy an unjustifiably expensive hacksaw for insulation, you can cut the insulation with the so-called bread knife with a wavy cutting edge. Moreover, the thinner its blade is, the less effort will need to be made to trim the slabs.

The order of installation work should be as follows.

  1. First of all, you need to make sure that the bottom plane of the rafter legs is in line. With noticeable deviations in geometry, leveling rails are stuffed onto the rafters.
  2. The entire plane of the roof slope is covered with moisture-proof material. This work is best done with a partner, attaching the film to the wood frame with a stapler. Laying must be carried out in the direction from the attic floor - with leaks and the appearance of condensation, moisture will not flow into the joints of the canvases. In this case, each next strip of waterproofing is admitted to the previous one by at least 10-15 cm and the joints are glued with tape.
    When installing waterproofing, make sure that the film is not attached with an interference fit. Otherwise, with the onset of cold weather, the material will shrink, causing ruptures at the points of attachment to the elements of the rafter system.

    Waterproofing should be taken care of even at the stage of installation of the roof - in this case, both a cake of thermal insulation and wooden elements of the rafter system will be under its protection

  3. The distance between the rafters is measured and the slabs are trimmed - they should be 2-3 cm wider than the opening. By the way, if the issue of roof insulation is taken care of at the design stage, then it will be possible to do without cutting stone wool. Thermal insulation manufacturers produce slabs 600 mm wide, so the pitch of the rafters should be no more than 570–580 mm.

    A special tool with a wavy cutting edge is best for cutting stone wool.

  4. The insulation is placed in the space between the rafters - there it will be held due to the bursting forces.

    Not only the effectiveness of insulation, but also the durability of the roofing cake depends on how correctly the thermal insulation is installed.

  5. If rock wool rolls are used or the angle of the roof slopes is less than 30 °, additional sagging insurance will be required... In this case, synthetic twine or thick fishing line will help to fix the thermal insulation. Like lacing, it is pulled between nails previously driven into a wooden frame.

    For fixing the insulation in the space between the rafters, a durable synthetic cord is best suited

The last stage is the installation of a vapor barrier. There is no need to describe this process in detail - the work is no different from installing waterproofing. The only point to which you should pay special attention is which side of the vapor barrier membrane will be adjacent to the seal. You can find the exact information in the instructions or on the packaging of the material.

A construction stapler with flat staples is best for attaching waterproofing and vapor barrier membranes.

The installation of decorative coating is carried out in accordance with the tasks of the room and the features of its interior. Finishing materials can be attached directly to the rafters (for plywood, OSB and chipboard), as well as mounted on counter-rails (for lining, siding) or galvanized metal profiles (gypsum plasterboards).

How to insulate the roof along the rafters

Insulation along the rafters from the inside is used in cases where it is required to strengthen the heat-insulating cake or to prevent the formation of cold transitions along the elements of the roof frame. To do this, the space between the rafters is filled with mineral wool of soft grades, and then the entire surface is covered with hard plates of expanded polystyrene or stone fiber.

Thermal insulation along the rafters is most often performed as part of the complex thermal insulation of attic rooms

Most often, the scheme of thermal insulation along the rafters is implemented during the construction of industrial buildings and is explained by the need to insulate the supporting metal roof frames.

The technology for laying thermal insulation into the roof frame does not differ from the method discussed above. Only after laying the insulation should you not rush to fix the vapor barrier. Before installing it, perform the following operations.

  1. A counter-lattice is installed, in the space between which hard mats of stone wool will be laid. The step between the timber or slats should be chosen so that the insulation plates are held by installing the rails. As for the section of lumber, it must correspond to the thickness of the thermal insulation.
  2. An additional layer of thermal insulation is laid. Installation is carried out in such a way that the joints between the plates of the upper and lower layers do not coincide - this will make the roofing cake more dense and will eliminate any gaps.

    In order for the insulation along the rafters to bring the maximum effect, the upper plates of thermal insulation must necessarily close the joints of the previous layer

    With a significant thickness of insulation, as well as when using thermal insulation of various types, experts recommend installing a vapor-tight membrane not only from the side of the room, but also along the line of contact of individual layers.
  3. The surface of the insulation is closed with a vapor barrier, after which they begin to install the decorative cladding.

The technology of two-layer installation with rafter insulation is the most expensive. Nevertheless, it is she who allows you to get the most effective thermal insulation and completely eliminate the possibility of heat transfer through the elements of the rafter system.

Secrets of the durability of the roofing cake in particular and the roof in general

  1. To prevent slabs of mineral wool from sagging and slipping, be sure to fix them with a nylon cord.
  2. When laying insulation in several layers, mount it with overlapping joints.
  3. The installation of the vapor barrier panels is performed with a reverse overlap, that is, in the direction from the ridge. In this case, the rising streams of warm, humid air will not enter the insulation layer. In addition, gluing the joints with special reinforced tape should not be neglected.
  4. When calculating the thickness of the insulation, the value is rounded up. According to experts, the minimum insulation thickness should be 20 cm.
  5. If the attic room has its own vertical walls and ceiling, then it is these surfaces that insulate, but not the roof slopes.
  6. When installing the thermal insulation cake, a counter-grill must be installed - with its help, the ventilation gaps are equipped. The minimum recommended thickness of counter battens on the roof side is 50 mm, and under the decorative sheathing - at least 20 mm.

Video: installation errors of insulation

For those who doubt the advisability of roof insulation with their own hands, we advise you to inquire about the cost of complex thermal insulation performed by construction companies. Depending on the complexity of the work, the price ranges from 300 to 500 rubles per square meter. And this is without taking into account the cost of purchasing the material. Agree that with such a simple technology, this money can be used more worthily.

House insulation with mineral wool

When autumn is already on the heels, the question of warming your home becomes acute. It is this vital topic that the next article will be devoted to. It is very important that when choosing a heater, do not rush and do not choose “which is cheaper”. Such a responsible issue should be approached with seriousness, and it is even better to consult with professionals in this field, so that they would advise you of really high-quality material.

How and what to insulate an attic in a private house

Table of contents of the article:

How to insulate the attic floor of a private house

Often the attic, due to its disorder, remains unused. But it is from the attic that you can make an excellent rest room or bedroom, if you correctly approach the choice of insulation and equip the attic yourself for living quarters. These issues can be resolved independently, or you can invite a team of builders who will be able to offer several options for insulating the attic of a wooden house, as well as ventilation devices for the attic floor.

Do-it-yourself foundation insulation - we build for ourselves: video

Marked "Foundation"

When choosing a material, it is worth correlating its service life with the service life of the foundation itself. Cheap foam, for example, lasts no more than 25 years, while concrete will last a century. It is believed that extruded polystyrene foam with the "Foundation" marking with protective sealed layers inside and at least 5 cm thick is optimal. Its predicted service life is 50-80 years.

The material is glued to the concrete surface with bitumen mastic or planted on specialized glue over a layer of roll waterproofing. (Unevenness of the concrete base is preliminarily leveled with cement mortar.) Additionally, the insulation is fixed with dowels. At the bottom of the pit, the thermal insulation is laid tightly end-to-end on the sand preparation and poured with concrete. Particular attention is paid to the corners, because it is they who are most exposed to freezing.

What is the best way to insulate the roof?

A comparative analysis of insulation for the roof, the study of the structural features of the roof will help to answer this question. The criteria to be met by the heat insulator:

  • low thermal conductivity
  • density
  • shape stability
  • corresponding thickness
  • low moisture permeability
  • ease
  • durability
  • resistance to sudden temperature changes
  • fire resistance
  • rodent resistance
  • environmental Safety.

Comparing the characteristics of the materials, you can easily determine which is the most suitable insulation to choose for the roof of the house.

The thickness of the insulation must be chosen based on the characteristics of the climate in the region. Usually, the thickness of the insulation on the roof varies from 50 to 150mm. For a more accurate calculation in these cases, a specialist is invited to avoid unnecessary mistakes.

Video for viewing which roof insulation to choose:

Recommendations for insulating a flat roof

This type of roof can be insulated from all sides. Insulation of the roof from the inside with mineral wool is best suited for external processing. In this case, when choosing materials, special attention should be paid to expanded polystyrene. It does not have the best resistance to fire and high temperatures.

Do-it-yourself roof insulation of this type from the inside is associated with the following procedures: laying a vapor barrier, tapping insulation, installing roll material (roofing material is perfect). Also, do not forget about the bulk layer. It is made from expanded clay and cement-sand mass.

In order to get acquainted with the step-by-step instructions for insulating a flat roof, you can find training videos.

Attic roof insulation

To insulate the attic roof with your own hands, insulating material is laid between the rafters. Rigid mineral wool slabs are most often used. They provide reliable protection and ease of installation. The distance between the rafters in cleanliness is taken 2 cm less than the width of the slab and it is held due to friction.

From below, for reliable fastening, a crate is performed, along which finishing work is being carried out. Above the insulation, it is necessary to provide an air gap to remove the resulting moisture. The size of such a layer is taken 3-5 cm. It is provided due to the height of the rafters or the installation of a counter-rail.

Competent insulation of the attic and attic space with your own hands can reduce heat losses and maintain the strength of structures for a long time, therefore it is so important to pay attention to both the floor and walls and the roof.

A great example of how you can turn an attic into a comfortable living space with the help of insulation:

Over time, each owner of a private house thinks about insulating the attic. After all, every year the materials lose their original qualities, which leads to the loss of heat, which goes through the attic.

Thermal insulation of the house is a priority that must be addressed before the onset of cold weather. So, as everyone knows that a warm house is not one that heats well, but one that does not let all this heat through.

It should also be noted that insulating the attic of a private house with polystyrene foam or any other insulation will make it possible to significantly reduce heating costs.

That is why the question of how and how to insulate the attic becomes extremely relevant.

The cost of ceiling insulation with mineral wool

Despite the simplicity of the technology, the work cannot always be done by hand. When ordering a service from a company, the owner should pay attention to the estimate. The price depends on:

  • area and volume of work
  • list of additional services.

Processing of wood with antiprenes, bioprotective compounds is mandatory. Also, the estimate includes preparation of the base: cleaning, priming, creating a frame and other additional services. If employees independently buy mineral wool for ceiling insulation, the price increases by the amount of the cost of the material. As a result, the average cost is from $ 10-16 per 1 m2, depending on external / internal work.

Watch the video: Tinyhouse insulation rockwool - Robs job tinyhouse build - Ep6

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