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

Thermal insulation of the floor with mineral wool in a wooden house is a responsible and rather complicated matter. The finished floor seems to guests just beautifully laid boards, giving the room a special chic and nobility. And only the owner of the house knows which complex construction lies under the 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 multi-layer structure that provides reliable waterproofing, protection from cold and overheating, insects and fungi, as well as providing strength and durability to the entire home. also in correct design a ventilation gap is needed to ensure air circulation. Depending on the floor wooden house, the 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 building dictate its requirements for the floors: the requirements for floors in the country, for example, are not as strict as for the coating in a private country wooden house. The attic floor is also different from the ground floor. The floor of the second floor is arranged differently from the floor of the first floor or attic. Most often, the floors are arranged in the form of a so-called cake, by analogy with the well-known puff pastry. One of the layers of the floor pie is a layer of thermal insulation, along with wood flooring, screed and other types of insulation.

Materials (edit)

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 insulation:

Expanded clay - a porous and lightweight material made of fired clay;
Sawdust - woodworking waste. Some of the cheapest materials. The cost of one installed m2 costs almost nothing;
Styrofoam - porous polymer material, lightweight and moisture resistant material. In addition to thermal insulation properties, there is also excellent waterproofing;
Penoplex - extruded polystyrene foam - is similar to polystyrene foam, but much more durable and it is believed that it is better in its properties, but has a higher price per m2;
Mineral wool- mineral fiber mats;
Glass wool - fiberglass mats, it is generally accepted 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 it is quite inconvenient to work with and has unimportant moisture-proof properties, and also has a high cost per m2. 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-insulating properties. In addition, which is important - 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 his own hands.

Mineral wool is supplied in rolls or mats of certain sizes and thicknesses. Mineral wool laminated with aluminum is also produced. The price of such wool per m2 is higher than that of ordinary wool. However, the cost of laying one m 2 does not differ from them. The thickness of this material varies from 50 mm to 200 mm and more, depending on the application. Unlike foam or Penoplek, mineral wool does not require preliminary cutting in shape and size. The roll is simply unrolled and the mineral wool is placed in the right place.

Sequencing

Thermal insulation of the floor with mineral wool is part of a multi-stage process for installing the floor, 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 the guides- wooden logs;
Insulation laying- filling each m2 of the floor with insulation material;
Laying the flooring is the last, finishing layer of the cake.

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 ground floor on the ground. In floor slabs, there are also irregularities and cracks. To eliminate irregularities in the first case, it is necessary to level the surface of the soil with a layer of rubble 10 cm thick, on which it is necessary to fill in a layer of sand of the same thickness.

You 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 irregularities and the associated uneven load on different parts of the floor surface. This circumstance forces to arrange a screed even in the attic.

Vapor barrier

A layer of vapor barrier on top of the screed must be laid in the floors of the premises on the first floor for each m2 of surface. This is necessary precisely when used as a mineral wool insulation. Mineral wool easily dampens, which leads to a decrease in its thermal insulation properties... Also when laying topcoat 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 the 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 coated with aluminum;
polypropylene film;
vapor barrier membranes.

Most often, polyethylene, polypropylene or aluminum coated film are used. This is primarily due to the cost of the material. However, the effectiveness of such a material is low, due to the possibility of condensate accumulation on its surface. This can lead to humidification of the mineral wool and, consequently, a decrease in its thermal insulation properties.

The most modern and reliable material is thick multi-layer vapor barrier membranes, made using a more sophisticated technology using many waterproofing materials... They are best used in country houses and cottages.

The vapor barrier layer is laid as evenly and tightly as possible to the surface of the floors and walls. In this case, there should be no ventilation gap. The 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 maintained on all floors, including the attic.

Warming

Mineral wool is placed on the first layer of vapor barrier. A roll of mineral wool is unwound and laid in such a way as not to leave ventilation gaps between the wool and the logs, as well as between the wool and the first layer of vapor barrier, no ventilation gap in order to avoid the accumulation of moisture on the mineral fiber.

This prevents the fiber from getting wet and the mineral wool loss of 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 it 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, despite the milder climate. The thickness of sheets of mineral wool 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.

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

Having laid a layer of mineral wool, it is necessary to lay another layer of vapor barrier on top of it. This is especially important when installing the floor in the attic of a house or summer 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 device of ventilation gaps - special holes between the sheets of the vapor barrier film, through which air will pass and moisture that has got under the vapor barrier will evaporate. Ventilation gaps are required 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, (the gables are also brick), with mineral wool insulation (150mm). This cake is from the inside outside - half a brick (125mm) + mineral wool insulation (150mm) + facing half a brick (125mm). Question -: is there a need for a ventilation gap between the mineral wool and the facing brick, if - no, will it dampen the walls and it will be damp in the house, I really don't want to make this ventilation gap. And is it enough bearing capacity the inner wall in half a brick ?? I ask you to answer in more detail, if possible, thanks in advance.
16.12.2009, 13:07
Green cat
But somehow it is generally wrong ...
16.12.2009, 14:25
Eliseev AS
17.12.2009, 00:05
jekson
The inner wall must be brick-thick.
The vent gap, in my opinion, is not needed. All the same, with time, nothing will remain of it - 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 brick, which means that nothing will accumulate anywhere.
Regarding whether half a brick is enough or not enough, look at chise 3. Everyone admires its excessive stability, but in fact it is the same as two walls in a half-brick, the main thing is not to forget to tie the walls
17.12.2009, 10:00
Eliseev AS
Dear tomcat_omsk. Minvata 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 + 150mm minvata + (without ventilation gap) half a brick, connecting together masonry mesh 50 * 50 * 3 in 5 rows .. Along the top in front of the ceilings, additionally reinforce the masonry with reinforcement 8-10 .. The foundation is shallow tape. The question on solidity probably disappears? Will the house be damp and will it dampen the corners? Just from the experience of operating a brick house from a well masonry with slag filling I know - it's damp, in cold weather, damp corners ... Or with mineral wool without a ventilation gap, everything will be OK ??? Please answer ...
17.12.2009, 11:14
tomcat_omsk
Again, IMHO, mineral wool has a greater vapor barrier than the inner part of a brick wall and moisture should not accumulate. Some comrades for fidelity between some bricks (in the outer wall) do not close vertical seams for fidelity, but this is not for everybody. If you plaster the interior walls, everything should be ok (vapor permeability will decrease even more).
In terms of strength, how many floors will your structure be? Where do you live? How are you with seismic?
17.12.2009, 11:16
tomcat_omsk
50 kg / m3 is not enough for the walls, you will have to increase the density by ramming the insulation (without fanaticism), otherwise it will 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, the flooring is wooden, 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 the insulation? 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
Minvata will be moistened not from rains, but from moisture from the house. She will come from a brick and leave through it in the direction of the house outside.
Vapor permeability outer wall not less than internal, facing brick is it ceramic? You need to work out this question.
The stability is more than sufficient. 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 armopoyas 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 nearby, so we have come to choose silicate
17.12.2009, 13:59
Eliseev AS
The question about the foundation is here, if possible.
I design the foundation according to Sazhin's book, bury the foundations in depth. The soil is up to 1.4-1.5 m, fine sand, then loam, clay, water at a depth of 0.8 to 1 m. Below is quicksand. The foundation for this house is obtained from the surface of the earth downwards - reinforced concrete 0.3 m high, 0.6 m wide, a pillow of coarse sand 0.5 m high and 1 m wide. I reinforce 3 bars of reinforcement at the top and bottom of the tape, diameter 12mm. I reinforce it transversely with a wire with a diameter of 4mm to create cells of 200 * 200mm. Does this option have a foundation for life ??? Freezing depth --- Nizhny Novgorod region On the top, as I wrote, there is an armored belt along the entire perimeter of the walls, its height is 300mm.
Will my foundation be strong enough ???
17.12.2009, 21:52
Andrey the teacher
18.12.2009, 08:41
Eliseev AS
Andrey 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 is - if God forbid it rains during laying and does not have time to cover it, will the cotton wool dry out normally later?
Why is it low on the foundation? one floor, the height of the masonry to the top is 3.60 m, the foundation is not strong enough?

Arkady Karpov, Moscow, asks about the cladding of a house: Hello, I would like to ask you a question. For me, the team is now making the cladding of the house, insulating and sheathing with siding. After the film has been laid, they immediately sew over this siding. I say - where is the gap? They say - don't, we always do that. Are they doing the right thing and how it should be done correctly?

The answer is Andrey Volokolamtsev, foreman of LLC "August", Podolsk.

Hello Arkady. Perhaps what your builders are doing is not quite right, or perhaps not at all right. So that you 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 do a ventilation gap and when.

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

Heaters of the type do not like moisture very much. When they get wet by at least 15 percent, they already lose 50 percent in their heat resistance indicators.

There are, however, insulation materials 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 sprayed onto the walls of the house.

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:

Use of any insulation that loses its properties when wet.
The material of the walls of the house allows steam to pass from the interior to the outer layer.
The 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 the ventilation gap can be omitted:

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

It is based on this ability of the facade plaster, when the walls can be insulated with foam or basalt wool.

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

When is a ventilation gap still necessary?

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

The decorative layer material promotes the formation of condensation.
The wall material under the decorative layer can deteriorate from moisture (rot, cracks, etc.).

Let me give you 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 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 air current, 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 you have, what kind of wall material.

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

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

Preventing the penetration of moisture into the mineral wool is a feasible task, but difficult. To do this, the fibrous insulation in the most dry state must be packed in a completely sealed casing. For example, in durable plastic bags... However, this is not so easy to do, and it is even more difficult to carefully mount the mineral wool without damaging the shell. Leaky bags are useless. 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 a roll bituminous waterproofing... As a rule, in overground structures of buildings, fibrous insulation is not so much isolated from the effects of moisture contained in the air, but rather they are trying to ensure the release of water vapor from the material. Consider in general outline the most common insulation designs country house:

Frame house. Both insulation and wooden frame need protection from waterlogging. Most of the year, the air inside the house has more high humidity than outside. Therefore, first of all on frame structure from the inside, over the entire area, an airtight vapor barrier film... As the name suggests, it is impervious to water vapor. But the insulation, not having an airtight shell, will absorb the moisture contained in the outside air. To prevent it from accumulating, it is necessary to provide a sufficiently effective ventilation of the mineral wool. At the same time, the wooden frame is also ventilated. To do this, between the casing and the insulation, fixing the bar, leave an empty gap. The recommended thickness of the ventilation gap is 40 mm; holes are arranged in the upper and lower parts of the walls, covering them with a mesh or lattice. 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.

The classic wall construction of a frame house. A vapor barrier is placed inside, excluding penetration humid air from the house to the insulation. Outside - a ventilated gap that allows moisture to escape from the mineral wool, covered with a windscreen

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

Correct thermal insulation of a wooden house: 1 - insulation; 2- windproof film; 3 - sheathing. Bars (counter-rail) are stuffed onto the frame, a ventilation gap is provided between the cladding and the windscreen, due to which the wood and mineral wool remain dry

Ventilated facade option - 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. It is similar to the thermal insulation system of a wooden house. The presence of a ventilation gap and wind insulation outside according to the scheme already known to us is mandatory. It is a little more complicated with vapor barrier: if the walls are made of non-hygroscopic (not absorbing moisture) material, vapor barrier is needed between the wall and the insulation. It is about reinforced concrete (including prefabricated panels) and expanded clay concrete blocks... If the walls are made of "breathing" materials, aerated concrete, brick - vapor barrier is not needed, it will only harm.

General arrangement of a ventilated facade

Plaster facade- hard mineral wool is attached directly to the wall, the plates are plastered on top. No vapor barrier is needed, and a thin-layer reinforced facade plaster serves as protection from precipitation and wind polymer mesh... You can only use special mixtures intended for external thermal insulation systems.

Now about the roof, consider only the pitched structures:

Combined (insulated) mansard roof. It is a frame structure, in many ways similar to the walls of a frame house. It is imperative that you need a vapor barrier from the inside, a ventilated gap and wind protection from the outside. When choosing a windproof film, it should be borne in mind that most roofing coatings are condensate-forming: dew or frost falls on the side facing the inside of the roof under certain conditions. Most of all, steel roofs sin this, sometimes the amount of condensate is very large. So that the water flowing from the roofing does not soak the insulation, special under-roofing films, the so-called diffusion membranes, are used as wind insulation. They have the property of freely passing water vapor outside, to prevent the penetration of liquid water inside. The drops simply roll down and flow off the roof.

The diffusion membrane has many pores. They are too shallow not to miss liquid water but large enough not to obstruct the escape of water vapor

An example of a combined pitched roof... To insulate the structure mansard roof has always remained dry, it must be ventilated. Ventilation (shown in the diagram by arrows) is carried out in the intervals between counter-rails packed along the rafters. From the bottom, the insulation should be protected by a vapor barrier (Izospan In the diagram), from the top - a diffusion membrane (Izospan AM).

Cold (not insulated) attic roof. Ventilation of the attic is organized through vents in the pediments, cracks in the filing, aerators in the covering. Since the roof is not insulated, only condensation protection is needed without the function of removing water vapor. The most rational thing is between roofing and rafter system place a vapor barrier film. A diffusion membrane will work too, but it is more expensive.

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