How to prevent moisture penetration into mineral wool. Do I need a vapor barrier when insulating with mineral wool from the outside and from the inside Answering the question of why a ventilation gap is needed

Warming the floor with mineral wool in a wooden house is a responsible and rather complicated matter. The finished floor seems to the guests just beautifully laid boards, giving the room a special chic and nobility. And only the owner of the house knows what complex structure lies under even rows of wooden floor boards and how much work needs to be invested in order to insulate the floor with your own hands and lay out the screed.

Floor device

A properly laid floor in a wooden house is a multilayer structure that provides reliable waterproofing, protection from cold and heat, insects and fungus, as well as providing strength and durability throughout the home. also in correct design Ventilation is needed to ensure air circulation. depending on the floor wooden house, floor arrangement may be different.

The floor on which the room is located, the degree of humidity, as well as the purpose of the entire structure also dictates its requirements for floors: the requirements for floors in a country house, for example, are not as strict as for a coating in a private country wooden house. The floor of the attic is also different from the floor of the first floor. The floor of the second floor is arranged differently than the floor of the first floor or attic. Most often, the floors are arranged in the form of a so-called pie, by analogy with the well-known puff pastry. One of the layers of the floor pie is the thermal insulation layer, along with wooden coverings, screed and insulation layers of other types.

materials

The floor insulation material is selected depending on the characteristics of the room (floor, purpose, humidity, floor material), as well as on the climatic conditions of the area in which the house is located.

The following materials are most often used as a heater:

Expanded clay is a porous and lightweight material made from fired clay;
Sawdust - woodworking waste. One of the cheapest materials. The cost of one m2 laid is almost worth nothing;
Styrofoam - porous polymer material, lightweight and moisture resistant material. In addition to thermal insulation properties, it also has excellent waterproofing;
Penoplex - extruded polystyrene foam - is similar to polystyrene, but much more durable and is considered to be better in its properties, but has a higher price per m2;
Mineral wool- mineral fiber mats;
Glass wool - fiberglass mats, it is considered that its thermal insulation is not much worse than that of mineral wool, but better performance waterproofing.

All of these materials have their own advantages and disadvantages. For example, polystyrene, with all its heat and waterproofing properties, has a fairly high fire hazard. Expanded clay is an excellent insulation, but rather inconvenient to use and has poor moisture-proof properties, and also has a high cost per m 2. And all these materials are still better than simple sawdust, although their use increases the cost of each m2 of flooring.

In mid-latitudes, the most acceptable option is mineral wool. This material has long been familiar to everyone, has high heat-shielding and sound-proofing properties. In addition, and not least, the price of one m 2 of mineral wool and, especially, the prices for laying m 2 are among the lowest among all building materials. The material is so easy to use that even a non-specialist can lay it with their own hands.

Mineral wool is supplied in rolls or mats in certain sizes and thicknesses. Mineral wool laminated with aluminum is also produced. The price of such cotton wool per m 2 is higher than that of ordinary wool. However, the cost of laying one m 2 they do not differ. The thickness of this material varies from 50 mm to 200 mm or more, depending on the application. Unlike polystyrene or Penoplek, mineral wool does not require pre-cutting in shape and size. The roll is simply unwound and the mineral wool is placed in the right place.

Sequencing

Mineral wool floor insulation is part of a multi-stage floor installation process, which is carried out according to the following algorithm:

Alignment. The surface on which the floor will be laid must be perfectly flat;
Vapor barrier - laying a layer of vapor barrier material;
Installing guides- wooden lag;
Insulation laying- filling each m2 of the floor with insulating material;
Laying the flooring is the last, finishing layer of the pie.

Actually, this whole process is carried out in order to ensure reliable insulation and waterproofing of the room. Therefore, it makes no sense to consider laying mineral wool separately from the other stages.

alignment

Leveling is especially important when laying the floor of the first floor on the ground. There are also irregularities and cracks in the floor slabs. To eliminate irregularities in the first case, it is necessary to level the soil surface with a layer of crushed stone 10 cm thick, on which it is necessary to fill in a layer of sand of the same thickness.

Should know. When laying the floor on reinforced concrete slabs floors, a leveling screed is usually used. The screed is usually used concrete or cement-sand. The absence of a screed can lead to the destruction of the entire floor due to unevenness and the uneven load associated with them on different parts of the floor surface. This circumstance makes it necessary to arrange a screed even in the attic.

vapor barrier

A layer of vapor barrier over the screed must be laid in the floors of the premises on the ground floor for every m2 of surface. This is necessary precisely when using mineral wool as a heater. Mineral wool easily dampens, which leads to a decrease in its thermal insulation properties. Same when setting finish coat it is important to observe the ventzaor between the mineral wool and the floor surface.

Roofing material can be used as a vapor barrier - it is better to use such material in the country, where the requirements for floors are mainly limited by the price of materials and all work is done by hand. Film waterproofing is used as modern and reliable materials for vapor barrier:

polyethylene film, including aluminum coated;
polypropylene film;
vapor barrier membranes.

The most commonly used polyethylene, polypropylene or film coated with aluminum. This is due primarily to the price of the material. However, the efficiency of such a material is low, due to the possibility of accumulation of condensate on its surface. This can lead to wetting of the mineral wool and, consequently, to a decrease in its thermal insulation properties.

The most modern and reliable material are multilayer vapor barrier membranes of large thickness, made using a more complex technology using many waterproofing materials. They are best used in country houses and cottages.

The vapor barrier layer is laid as evenly and densely as possible to the surface of ceilings and walls. In this case, there should not be any ventilation gap. Holes in the bottom layer of the vapor barrier will not lead to ventilation, but to the appearance of moisture on the insulation layer. This principle is preserved on all floors, including the attic.

Warming

Mineral wool is laid on the first layer of vapor barrier. The mineral wool roll is unwound and laid in such a way that no ventilation gaps are left between the wool and the joists, and there is no ventilation gap between the wool and the first layer of vapor barrier to prevent moisture accumulation on the mineral fiber.

This prevents the fiber from getting wet and the mineral wool from losing its heat-insulating properties. The technology provides for the installation of special ventilation gaps between the insulation and the second layer of vapor barrier.

The thickness of the mineral wool sheet is selected depending on the purpose of the building and climatic conditions. So, in the country, used mainly only in warm time years is enough to apply mineral wool 50 mm thick. The same applies to technical buildings and houses in the southern regions, where it is still impossible to do without insulation at all, despite the milder climate. The thickness of mineral wool sheets used on the second and third floors, in the attic or in the attic may also not exceed 5 cm. This is due to lower requirements for floor insulation on the floors, as well as the need to preserve the volume of the room.

Note. In private country houses, it is better to use cotton wool 200 mm thick. Cotton wool of this thickness will provide reliable thermal insulation.

After laying a layer of mineral wool, it is necessary to lay another layer of vapor barrier on top of it. This is especially important when arranging the floor in the attic of a house or cottage. However, here the laying technology will be somewhat different than in the first layer. To ensure ventilation in order to avoid the accumulation of moisture on the insulation layer, the technology provides for the installation of ventilation gaps - special holes between the sheets of vapor barrier film through which air will pass and moisture that has fallen under the vapor barrier will evaporate. Ventilation gaps are needed between all sheets of film or membrane.

16.12.2009, 10:16
Eliseev AS
Ventilation gap in three-layer walls

Hello, help who can ... I'm going to build a one-story brick house 10 * 9m, (pediments are also brick), with mineral wool insulation (150mm). This cake is from the inside to the outside - half a brick (125mm) + mineral wool insulation (150mm) + half a facing brick (125mm). The question is: do I need a ventilation gap between the mineral wool and the facing brick, if - no, will the walls be damp and damp in the house, I really don’t want to make this ventilation gap. And is it enough bearing capacity interior wall in half a brick?? Please answer in more detail if possible, thanks in advance.
16.12.2009, 13:07
Green Cat
Yes, it's kind of wrong...
16.12.2009, 14:25
Eliseev AS
17.12.2009, 00:05
jekson
The inner wall must be brick-thick.
The vent is not needed in my opinion. Anyway, with time, nothing will remain of it - the mineral wool will fill the void.
17.12.2009, 09:19
tomcat_omsk
Pour granulated foam glass instead of cotton wool and do not need any gaps. This insulation has similar properties as a brick, which means that nothing will accumulate anywhere.
Regarding whether half a brick is enough or not enough, look at tise 3. Everyone admires its excessive stability, but in fact it is the same as two half-brick walls, the main thing is not to forget to tie the walls
17.12.2009, 10:00
Eliseev AS
Dear tomcat_omsk. Mineral wool has already been purchased - Izorok with a density of 50KG / M3, i.e. granulated foam glass disappears .. If I do this --- from the inside - half a brick + 150 mm mineral wool + (without a ventilation gap) half a brick, interconnecting masonry mesh 50 * 50 * 3 after 5 rows .. On the top, in front of the ceilings, additionally reinforce the masonry with reinforcement 8-10 .. The foundation is shallowly buried tape. Will it be damp in the house and will the corners be damp? Just from the experience of operating a brick house made of well masonry with slag backfill, I know - it’s damp, damp corners in cold weather ... Or will everything be OK with mineral wool without a ventilation gap ??? Please reply...
17.12.2009, 11:14
tomcat_omsk
Again, IMHO, mineral wool has a greater vapor barrier than the inside of a brick wall and moisture should not accumulate. Some comrades for fidelity between some bricks (in the outer wall) do not close up vertical seams for fidelity, but this is not for everyone. If you plaster the inner walls, everything should be ok (vapor permeability will still decrease).
Regarding strength, how many floors will your building be? Where do you live? How are you with seismic?
17.12.2009, 11:16
tomcat_omsk
50 kg / m3 is something not enough for walls, you will have to increase the density by tamping the insulation (without fanaticism), otherwise it will noticeably settle
17.12.2009, 11:40
Eliseev AS
Cottage 10 * 9m on the outer walls, brick gables (half-brick) in the future I plan residential attic, wooden floors, the location of the house is the Nizhny Novgorod region, those earthquakes are not expected ....
17.12.2009, 11:43
Eliseev AS
The density of the mineral wool was taken according to the manufacturer's recommendations, Rockwell generally recommends caviti with a density of 45 units., For layered masonry.
During prolonged rains, the masonry will not get wet and with it a heater? If so, is it not fatal for mineral wool? And how will all this evaporate from there and affect the insulation?
17.12.2009, 12:28
tomcat_omsk
Mineral wool will be moistened not from rain, but from moisture from the house. She will come from a brick and leave through it in the direction from the house to the outside.
Vapor permeability outer wall no less than internal facing brick is it ceramic? You need to work on this issue.
The stability is more than adequate. If you were building two-storey house with reinforced concrete floors, then probably half a brick on inner wall it would not be enough, and then the reinforced concrete armored belt would solve this problem.
17.12.2009, 13:35
Eliseev AS
Silicate brick, both internal and outer wall, it's just that there is no ceramics factory near us, it is necessary to choose silicate
17.12.2009, 13:59
Eliseev AS
Question about the foundation here, if possible.
I am designing a foundation according to Sazhin's book, bury foundations deep into. The soil is up to 1.4-1.5m fine sand, then loam, clay, water at a depth of 0.8 to 1m. Below is a swimmer. The foundation for this house is obtained from the surface of the earth down - reinforced concrete 0.3 m high, 0.6 m wide, a pillow of coarse sand 0.5 m high, 1 m wide. I reinforce 3 bars of reinforcement at the top and bottom of the tape with a diameter of 12mm. I reinforce transversely with wire with a diameter of 4 mm to create cells 200 * 200 mm. Does such an option have a foundation for life ??? Freezing depth --- Nizhny Novgorod region. On the top, as he wrote, there is an armored belt around the entire perimeter of the walls, its height is 300mm.
Will my foundation be strong enough???
17.12.2009, 21:52
Andrew teacher
18.12.2009, 08:41
Eliseev AS
Andrei is a teacher, I took into account the thickness of the insulation. for the Nizhny Novgorod region. the thickness turns out to be about 130 mm in layered masonry, I took 150 mm, I hope it will be enough? Cotton wool will not dry at all or slowly?
And the question --- if, God forbid, it rains during laying and I don’t have time to cover it, will the cotton wool then dry out normally?
On the foundation, why low? one floor, the height of the masonry to the top is 3.60m, is the foundation not strong enough?

Arkady Karpov, Moscow, asks a question about the cladding of the house: Hello, I want to ask you a question. Now the team is doing the sheathing of the house for me, they are insulating and sheathing with siding. After the film has been laid, the siding is immediately sewn on top of this. I say - where is the gap? They say no, we always do it. Are they doing the right thing and how to do it right?

Andrey Volokolamtsev, foreman of Avgust LLC, Podolsk, answers.

Hello Arkady. Perhaps what your builders are doing is not quite right, and perhaps not at all right. In order for you to have a normal and systematic understanding of this issue, let's first analyze your case, and then we'll see if it is necessary to make a ventilation gap and when.

So let's figure it out. If the walls are made of a vapor-permeable material, then in the case of using a decorative layer of siding, you definitely need to make a ventilated gap. Because the moisture interior spaces your house in the form of steam will penetrate through the walls into the insulation and moisten it.

Type heaters do not like moisture very much. When they get wet by at least 15 percent, they already lose 50 percent of their thermal resistance.

There are, however, such heaters that are not so susceptible to moisture, which do not lose their heat-insulating ability so much. This primarily applies to polyurethane foam, which can be applied to the walls of the house by spraying.

When exactly is a ventilation gap needed?

So, in your case, the ventilated gap between the insulation and the outer decorative layer will definitely be needed in the following options:

The use of any insulation that loses its properties when wet.
The material of the walls of the house passes steam from the interior to the outer layer.
Decorative finish is a layer of vapor barrier or moisture-condensing material.

The last point can be fully attributed to vinyl siding, metal siding and profiled sheet. These materials will not allow moisture to escape from the insulation if they are tightly sewn onto the insulation layer.

When is a ventilation gap not needed?

In what cases can a ventilation gap be omitted:

The material of the walls of the house does not let steam from the interior to the outside, for example, concrete.
The insulation from the interior is well insulated with a vapor barrier.
The outer material is highly permeable to steam, e.g. facade plaster.

This ability of facade plaster is built when the walls can be insulated with foam plastic or basalt wool.

Any steam that enters the insulation is removed directly through the plaster layer and vapor-permeable paint. In this case, there is no ventilation gap between the insulation and the decorative layer.

When else is a ventilation gap necessary?

In what other cases will you need a ventilation gap between the wall and the decorative coating:

The material of the decorative layer contributes to the formation of condensate.
The material of the walls under the decorative layer can deteriorate from moisture (rot, cracks, etc.).

I will give a simple example. If you are planning to sheathe a wooden house with a metal profiled sheet, then you cannot do without a ventilation gap.

Otherwise, all the moisture that will condense on the inner surface of the profiled sheet will be absorbed, which will be destroyed from this.

In the case of a ventilation gap, moisture, of course, condenses on the inner surface of the profiled sheet - this is metal. But it does not have direct contact with the surface of wooden walls. And the current of air, which is present in the ventilation gap, carries away this moisture in the form of steam and removes it from the space between the decorative layer and the wall.

Consider which of the above cases is yours, and choose whether you need a ventilation gap or not. See what kind of wall material you have.

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We always ask our readers to “decipher” questions, provide additional data that would help to understand what the problem is. For example, what exactly are you asking about? It's understandable that you want the fiber insulation to stay dry. But what is the design of the thermal insulation of the house? Do you insulate the frame by putting mineral wool between the racks? Or is it a brick house with external insulation? Or maybe wooden frame? Or internal insulation? Are you interested in the roof? Then which one: combined attic or cold attic? There are many options for thermal insulation of buildings and as many answers to your question. Alas, one-stop solution no.

Without going into the specifics of specific designs, we will try to give general idea how to keep the insulation dry. In this case, we will assume that precipitation or water from the soil in building construction your house is not penetrated, the roof does not leak, there are no holes in the lining of the walls, the walls are waterproofed from the foundation, etc. We will not consider the insulation of the building from the inside as irrational.

To prevent the penetration of moisture into the mineral wool is a task, although feasible, but difficult. To do this, the fibrous insulation in the most dry state must be packed in a completely sealed shell. For example, in strong plastic bags. However, this is not so easy to do, and carefully mounting the mineral wool without damaging the shell is even more difficult. From leaky bags there is no sense. Therefore, complete protection against moisture penetration is rarely used. An example of such a solution is the insulation of heating mains, where the shell is roll bituminous waterproofing. As a rule, in the aboveground structures of buildings, fibrous insulation is not so much isolated from the effects of moisture contained in the air, as they try to ensure the release of water vapor from the material. Consider in in general terms the most common insulation designs country house:

Frame house. Both a heater and wooden frame need protection from waterlogging. For most of the year, the air inside the house has more than high humidity than outside. Therefore, first of all frame structure from the inside, an airtight seal is fixed over the entire area vapor barrier film. As the name implies, it is impervious to water vapor. But the insulation, not having a sealed shell, will absorb the moisture contained in the outside air. So that it does not accumulate, it is necessary to ensure sufficiently effective ventilation of mineral wool. At the same time, the wooden frame is also ventilated. To do this, between the skin and the insulation, having fixed the bar, leave an empty gap. The recommended thickness of the ventilation gap is 40 mm; holes are made in the upper and lower parts of the walls, covering them with a mesh or grate. To prevent gusts of wind from blowing through the insulation, a windproof film is attached on top of it, which does not prevent water vapor from escaping to the outside.

Classic frame house wall construction. A vapor barrier is placed inside to prevent penetration humid air from the house to the heater. Outside - a ventilated gap that ensures the removal of moisture from the mineral wool, closed by a windshield

Wooden house, external insulation: a frame filled with mineral wool and sheathing on top of it. The walls of the log house, made of wood, need protection from moisture no less than fibrous insulation. “Packing” them from the inside with a vapor barrier is irrational, the benefits are lost natural wood. Place a vapor barrier between log wall and insulation is also not worth it, this can lead to waterlogging of the wood and damage to it by a fungus. We have to put up with the fact that water vapor will constantly penetrate into wooden walls from inside the house and go outside through the insulation. To effectively remove this moisture, we do, as is the case with frame house, ventilation gap. We close the mineral wool with a windshield. Again, when insulating a log house, vapor barrier is not needed.

Proper thermal insulation of a wooden house: 1 - insulation; 2- windproof film; 3 - sheathing. Bars (counter-rail) are stuffed on the frame, a ventilation gap is provided between the sheathing and wind protection, thanks to which the wood and mineral wool remain dry

Variant of ventilated facade - multilayer stone wall made of aerated concrete with brick cladding. There is a ventilation gap and wind insulation. In the lower and upper areas of the cladding, it is necessary to leave ventilation holes sufficient area

Stone house, ventilated facade. Similar to the thermal insulation system of a wooden house. The presence of an outside ventilation gap and wind insulation according to the scheme already known to us is mandatory. With vapor barrier it is a little more difficult: if the walls are made of non-hygroscopic (non-moisture-absorbing) material, a vapor barrier is needed between the wall and the insulation. We are talking about reinforced concrete (including prefabricated panels) and expanded clay concrete blocks. If the walls are made of "breathable" materials, cellular concrete, bricks - vapor barrier is not needed, it will only harm.

General arrangement of a ventilated facade

Stucco facade- rigid mineral wool is attached directly to the wall, plastered on top of the slabs. Vapor barrier is not needed, and thin-layer reinforced facade plaster serves as protection against precipitation and wind polymer mesh. Only special mixtures intended for external thermal insulation systems can be used.

Now about the roof, consider only pitched structures:

Combined (insulated) mansard roof. It is a frame structure, in many respects similar to the walls of a frame house. Be sure to need a vapor barrier from the inside, a ventilated gap and wind protection from the outside. When choosing a wind insulation film, it should be taken into account that most roof coverings are condensate-forming: on the side facing the inside of the roof, under certain conditions, dew or frost falls. Most of all, steel roofs sin with this, sometimes the amount of condensate is very large. So that the water flowing from the roofing does not soak the insulation, special roofing films, the so-called diffusion membranes, are used as wind insulation. They have the ability to freely pass water vapor to the outside, to prevent the penetration of liquid water inside. Drops simply roll down and flow out of the roof.

The diffusion membrane has many pores. They are too small not to miss liquid water, but large enough not to prevent water vapor from escaping

An example of a combined pitched roof. To insulate in the design mansard roof always remained dry, it is necessary to ensure its ventilation. Ventilation (shown in the diagram by arrows) is carried out in the intervals between the counter-rails, stuffed along the rafters. From below, the insulation should be protected by a vapor barrier (Izospan On the diagram), from above - a diffusion membrane (Izospan AM).

Cold (uninsulated) attic roof. Ventilation of attic spaces is organized through vents in the gables, slots in the filing, aerators in the coating. Since the roof is not insulated, only protection against condensate is needed without the function of removing water vapor. The most rational between roofing and truss system place a vapor barrier. Diffusion membrane is also suitable, but it is more expensive.

If you have any questions, we are ready to answer them. Urgent request: specify, please, your messages. In a question-and-answer format, it is difficult for us to give answers to general questions. Yes, and you probably do not get the information of interest in full.