Ventilation gap for mineral wool. Insulation of floors with mineral wool and vapor barrier technology

When insulating walls using the “ventilated facade” system, the insulation is constantly washed by a stream of air. That's why the most important characteristic The insulation used is its breathability. You need to know how freely air can move inside the insulation itself. And that means reducing thermal insulation characteristics layer, or even create “its disappearance”. Depending on breathability mineral wool It may be necessary to use windproof membranes.

In a ventilated façade

When insulating using the “ventilated facade” system, the insulation is pressed against the wall using anchors, planks hung on the wall, etc. Between the insulation and external finishing left ventilation gap.

If the system is assembled correctly, then under the influence of heat passing through the heat insulator, as well as due to wind pressure, a natural, stable draft of air from bottom to top occurs in the ventilation gap.

In the system curtain façade with a ventilation gap, the insulation is constantly exposed to air moving along the ventilation gap. But the air moves from bottom to top and through the insulation layer, i.e. directly on the insulation. And the greater the breathability of this material, the greater the amount of air will pass through it.

Heat escapes with the air

This movement of air through the insulation is essentially a direct leakage of heat from the building, reducing the effect of insulation. This is the so-called convection heat transfer by air, a phenomenon that reduces the heat transfer resistance of the building envelope using the “ventilated facade” system by 20% or more.

If, during installation, tight contact of the insulation with the wall was not ensured, then convection heat loss increases significantly, and the effect of the insulation is reduced by 40 - 60%. This is a very serious problem when insulating buildings using this technology.

Air flow speed and wind zones

Also, losses will increase with increasing speed of air movement through the ventilation gap. There is a significant increase in convection heat loss in the insulation layer in areas where there are frequent winds (6 – 7 wind zones) or for high-rise buildings (70 m from ground level) in any wind zone.

In which insulation materials based on basalt wool do significant convection heat losses occur?

Density of mineral wool

For slabs made of basalt fiber with a density of 80 kg/m3 or more, this problem practically ceases to exist. Its manifestations can only occur if the insulation is not completely pressed against the wall, then it is possible to increase heat loss by up to 5%, but due to the movement of air in the cracks between the insulation and the wall.

Now it can be argued that when using mineral wool slabs with a density of 80 kg/m3 or more for insulation, convection heat loss will not be more than 2.5%.

Thus, the specified density of basalt slabs is limiting for problem-free operation in a ventilated facade system. And such slabs can be used without additional wind protection - without a superdiffusion membrane.

Should I use a membrane?

Sufficient resistance to air permeation can be achieved either by using a high-density heat insulator, or by increasing the resistance of the layer for air movement by installing additional windproof membrane.

Which way to solve the problem is better?

Use denser, and therefore more expensive, insulation in a thicker layer, or hang additional element systems, which, by the way, can become unusable and, at a minimum, create fire problems?

There is an opinion that it is better to use denser mineral wool, without an additional membrane, and, if required, in areas with significant wind loads, install basalt fiber insulation with a density of 180 kg/m3.

The problem of reducing heat loss from air convection must be solved by using insulation materials with appropriate characteristics.

What is more expensive and more effective – a membrane or...

The insulation itself will of course be more expensive, but taking into account the absence of a membrane, the increase in price will not exceed 2% of the cost of the entire ventilated facade system. At the same time, the reliability of the system increases significantly.

It should be noted that two-layer insulation can be used, in which cheaper and more warm layer, covered with a wind-resistant dense layer. But this option requires a higher construction standard and the absence of gaps between the slabs during installation, which is difficult to ensure in practice.

At the same time, the use of single-layer insulation is more technologically advanced, and an increase in the cost of the entire system at the level of 2% should not affect the feasibility of this particular “ventilated facade” insulation technology.

Today, there are no standards and construction rules that would determine when it is possible to do without a windproof membrane in a ventilated façade system, and when it is not.

Insulating the floor with mineral wool in a wooden house is a responsible and quite complicated task. The finished floor appears to guests as simply beautifully laid boards, giving the room a special chic and nobility. And only the owner of the house knows what complex design lies under the even rows of wooden floor boards and how much work needs to be put in to insulate the floor with your own hands and lay out the screed.

Floor construction

A correctly 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, a proper design requires a ventilation gap 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 structure also dictates its requirements for floors: the requirements for floors in a country house, for example, are not as strict as for the flooring 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 constructed 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 product. One of the layers of the floor cake is a layer of thermal insulation, along with wooden coverings, screed and other types of insulation layers.

Materials

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

The following materials are most often used as insulation:

Expanded clay is a porous and lightweight material made from baked clay;
Sawdust is a waste product from wood processing. Some of the cheapest materials. The cost of one laid m2 is almost nothing;
Polystyrene foam is a porous polymer material, lightweight and moisture-resistant. In addition to thermal insulation properties, it also has excellent waterproofing;
Penoplex - extruded polystyrene foam - is similar to polystyrene foam, but is much more durable and is considered to have better properties, but has more high price per m2;
Mineral wool- mats made of mineral fibers;
Glass wool is a mat made of fiberglass; it is generally accepted that its thermal insulation is not much worse than that of mineral wool, but its waterproofing performance is better.

All these materials have their advantages and disadvantages. For example, polystyrene foam, for all its thermal and waterproofing properties, has a fairly high fire hazard. Expanded clay is an excellent insulation material, but it is quite inconvenient to work with and has poor 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; it has high heat-protective and sound-proofing properties. In addition, what is important is that the price of one m2 of mineral wool and, especially the prices for laying m2, are among the lowest among all building materials. The material is so easy to use that even a non-specialist can install it with his own hands.

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

Sequence of actions

Floor insulation with mineral wool 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;
Installation of guides- wooden logs;
Laying insulation- filling each m2 of floor with insulating material;
Laying the flooring is the last, finishing layer of the cake.

Actually, this entire process is carried out with the aim of ensuring reliable insulation and waterproofing of the room. Therefore, there is no point in considering the laying of mineral wool separately from the other stages.

Alignment

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

You should know. When laying the floor on reinforced concrete slabs floors, a leveling screed is usually used. The screed is usually concrete or cement-sand. The absence of a screed can lead to the destruction of the entire floor due to unevenness and the associated uneven load on different areas floor surface. This circumstance forces us to install 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 first floor premises on every m2 of surface. This is necessary precisely when using mineral wool as insulation. Mineral wool easily becomes damp, which leads to a decrease in its thermal insulation properties. Also, when laying the finishing coating, it is important to maintain a ventilation gap between the mineral wool and the floor surface.

You can use roofing felt as a vapor barrier - this material is best used in a country house, where the requirements for flooring 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 those coated with aluminum;
polypropylene film;
vapor barrier membranes.

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

The most modern and reliable material are multi-layer vapor barrier membranes of great thickness, made to a higher standard. complex 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 ceilings and walls. In this case, there should be no ventilation gap left. Holes in the lower layer of 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.

Insulation

Mineral wool is laid on the first layer of vapor barrier. The mineral wool roll is unwound and laid in such a way as to leave no ventilation gaps between the wool and the joists, and also no ventilation gap between the wool and the first layer of vapor barrier to avoid the accumulation of moisture on the mineral fiber.

This prevents the fiber from getting wet and the mineral wool from losing its thermal insulation 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 a country house that is used mainly only in the warm season, it is enough to use mineral wool 50 mm thick. The same applies to technical buildings and houses in southern regions, where it is still impossible to do without insulation completely, despite the milder climate. The thickness of mineral wool sheets used on the second and third floors, in the attic or 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 maintain the volume of the room.

FYI. In private country houses it is better to use cotton wool with a thickness of 200 mm. Cotton 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 a floor in the attic of a house or cottage. However, here the laying technology will be slightly different than in the first layer. To ensure ventilation and avoid the accumulation of moisture on the insulation layer, the technology provides for the construction of ventilation gaps - special holes between the sheets of vapor barrier film through which air will pass and moisture trapped under the vapor barrier will evaporate. Ventilation gaps are needed between all sheets of film or membrane.

Ventilation gap in frame house- this is a moment that often raises many questions among people who are involved in insulating their own home. These questions arise for a reason, since the need for a ventilation gap is a factor that has a huge number of nuances, which we will talk about in today’s article.

The gap itself is the space that is located between the sheathing and the wall of the house. A similar solution is implemented using bars that are attached on top of the wind barrier membrane and on the external finishing elements. For example, the same siding is always attached to bars that make the facade ventilated. A special film is often used as insulation, with the help of which the house, in fact, is completely wrapped.

Many will rightly ask, is it really not possible to just take and attach the sheathing directly to the wall? Do they just line up and form an ideal area for installing sheathing? In fact, there are a number of rules that determine the necessity or unnecessaryness of organizing a ventilation facade. Let's figure out whether a ventilation gap is needed in a frame house?

When is a ventilation gap (vent gap) needed in a frame house?

So, if you are thinking about whether a ventilation gap is needed in the facade of your carcass house, pay attention to the following list:

When wet If the insulation material loses its properties when wet, then a gap is necessary, otherwise all work, for example, on insulating a home, will be completely in vain
Steam Permeation The material from which the walls of your home are made allows steam to pass into the outer layer. Here, without organizing free space between the surface of the walls and insulation, it is simply necessary.
Preventing excess moisture One of the most common questions is the following: is there a need for a ventilation gap between vapor barriers? If the finish is a vapor barrier or moisture-condensing material, it must be constantly ventilated so that excess water is not retained in its structure.

As for the last point, the list of similar models includes following types sheathing: vinyl and metal siding, profiled sheets. If they are tightly sewn onto a flat wall, then the remaining accumulated water will have nowhere to escape. As a result, materials quickly lose their properties and also begin to deteriorate externally.

Is there a need for a ventilation gap between siding and OSB?

When answering the question of whether a ventilation gap is needed between the siding and OSB (from English - OSB), it is also necessary to mention its need. As already stated, siding is a product that insulates vapor and OSB board consists entirely of wood shavings, which easily accumulates residual moisture and can quickly deteriorate under its influence.

Additional reasons to use a ventilation gap

Let's look at a few more mandatory points when clearance is a necessary aspect:

Preventing rot and cracks The wall material under the decorative layer is prone to deformation and deterioration when exposed to moisture. To prevent rot and cracks from forming, just ventilate the surface, and everything will be fine.
Preventing condensation The material of the decorative layer may contribute to the formation of condensation. This excess water must be removed immediately.

For example, if the walls of your house are made of wood, then an increased level of moisture will negatively affect the condition of the material. Wood swells, begins to rot, and microorganisms and bacteria can easily settle inside it. Of course, a small amount of moisture will collect inside, but not on the wall, but on a special metal layer, from which the liquid begins to evaporate and be carried away with the wind.

Is there a need for a ventilation gap in the floor? No

Here you need to take into account several factors that determine whether you need to make a gap in the floor:

If both floors of your house are heated, then a gap is not necessary If only the 1st floor is heated, then it is enough to lay a vapor barrier on its side to prevent condensation from forming in the ceilings.
The ventilation gap must be attached only to the finished floor!

When answering the question of whether a ventilation gap is needed in the ceiling, it should be noted that in other cases this idea is purely optional and also depends on the material chosen for insulating the floor. If it absorbs moisture, then ventilation is simply necessary.

When a ventilation gap is not needed

Below are a few cases where this construction aspect does not need to be implemented:

If the walls of the house are made of concrete If the walls of your house are made, for example, of concrete, then you don’t need to make a ventilation gap, because this material does not allow steam to pass from the room to the outside. Consequently, there will be nothing to ventilate.
If there is a vapor barrier inside the room If with inside If the room has a vapor barrier installed, then the gap also does not need to be organized. Excess moisture simply will not come out through the wall, so there is no need to dry it.
If the walls are treated with plaster If your walls are treated, for example, with facade plaster, then a gap is not needed. In case outer material processing allows steam to pass through well, additional measures It is not required to ventilate the casing.

Installation example without ventilation gap

As a small example Let's look at an example of installation without the need for a ventilation gap:

At the beginning there is a wall
Insulation
Special reinforcing mesh
Mushroom dowel used for fastening
Facade plaster

Thus, any amounts of steam that penetrate the structure of the insulation will be immediately removed through the layer of plaster, as well as through vapor-permeable paint. As you may have noticed, there are no gaps between the insulation and the decoration layer.

We answer the question why a ventilation gap is needed

The gap is necessary for air convection, which can dry out excess moisture and have a positive effect on the safety of building materials. The very idea of this procedure is based on the laws of physics. Ever since school we have known that warm air always goes up and cold always goes down. Consequently, it is always in a circulating state, which prevents liquid from settling on surfaces. In the upper part, for example, of the siding sheathing, perforations are always made, through which steam escapes out and does not stagnate. It's very simple!

A question about house cladding is asked by Arkady Karpov, Moscow: Hello, I want to ask you a question. Now a team is doing the sheathing of my house, insulating it and covering it with siding. After laying the film, siding is immediately sewn on top of it. I say – where is the gap? They say no, we always do this. Are they doing the right thing and doing it the right way?

Answered by Andrey Volokolamtsev, foreman of Avgust LLC, Podolsk.

Hello, Arkady. Perhaps what your builders are doing is not entirely correct, or perhaps it is not at all correct. So that you have a normal and systematic understanding of this issue, let’s first look at your case, and then see if a ventilation gap needs to be done and when.

So let's figure it out. If the walls are made of vapor-permeable material, then if you use a decorative layer of siding, you must make a ventilated gap. Because the moisture from interior spaces your home in the form of steam will penetrate through the walls into the insulation and moisten it.

This type of insulation does not like moisture very much. When they get wet by at least 15 percent, they already lose 50 percent in their thermal resistance.

There are, however, insulation materials that are not so susceptible to moisture and that do not lose their heat-insulating ability as much. This primarily applies to polyurethane foam, which can be sprayed onto the walls of a house.

When exactly is a ventilation gap needed?

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

The 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.
Decorative finishing is a layer of vapor barrier or moisture-condensing material.

The last point can be fully attributed to vinyl siding, metal siding and profiled sheets. 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 allow steam to pass from the interior to the outside, for example, concrete.
The insulation on the interior side is well insulated with a vapor barrier.
External material allows steam to pass through well, for example, facade plaster.

On this ability facade plaster it is built when the walls can be insulated with foam plastic or basalt wool.

Any vapor that gets into the insulation is released 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 covering:

The material of the decorative layer 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 cover a wooden house with a metal profiled sheet, then you cannot do without a ventilation gap.

Otherwise, all the moisture that will condense on inner surface corrugated sheet will be absorbed, which will be destroyed as a result.

In the case of a ventilation gap, moisture, of course, condenses on the inner surface of the profiled sheet - this is metal. But direct contact with the surface wooden walls does not have. And the air current that 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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16.12.2009, 10:16
Eliseev AS
Ventilation gap in three-layer walls

Hello, can anyone help me... I'm going to build a one-story brick house, 10*9m, (the gables are also brick), with mineral wool insulation (150mm). The cake is like this - from the inside to the outside - half a brick (125mm) + mineral wool insulation (150mm) + half a facing brick (125mm). The question is: is there a need for a ventilation gap between the mineral wool and the facing brick, if not, will the walls become damp and humid in the house? I really don’t want to make this ventilation gap. And will it be enough? bearing capacity half a brick interior wall?? Please answer in more detail if possible, thanks in advance.
16.12.2009, 13:07
Green Cat
Yes, somehow it’s completely wrong...
16.12.2009, 14:25
Eliseev AS
17.12.2009, 00:05
jackson
The internal wall must be made brick thick.
The ventilation gap, in my opinion, is not needed. All the same, over time, there will be nothing left of it - mineral wool will fill the void.
17.12.2009, 09:19
tomcat_omsk
Use granulated foam glass instead of cotton wool and you don’t need any gaps. This insulation has similar properties as brick, which means nothing will accumulate anywhere.
Regarding whether half a brick is enough or not, look at Tise 3. Everyone admires its excessive stability, but in essence it is the same as two half-brick walls, the main thing is not to forget to connect the walls
17.12.2009, 10:00
Eliseev AS
Dear tomcat_omsk. Mineral wool has already been purchased - Isorok with a density of 50KG/M3, i.e. granulated foam glass disappears.. If I do this --- from the inside - half a brick + 150mm mineral wool + (without a ventilation gap) half a brick, connecting each other with a masonry mesh 50*50*3 through 5 rows.. Along the top in front of the ceilings, additionally reinforce the masonry with 8-10 reinforcement.. The foundation is a shallow strip foundation. The question of strength probably disappears? The question is again about humidity?? Will it be humid in the house and will the corners get damp? I just know from the experience of operating a brick house made of well masonry filled with slag - it’s a bit damp, the corners are damp in cold weather... Or will everything be OK with mineral wool without a ventilation gap??? Please answer...
17.12.2009, 11:14
tomcat_omsk
Again, IMHO, mineral wool has greater vapor permeability than inner part The walls are made of brick and moisture should not accumulate. Some comrades, to be sure, do not seal the vertical seams between some bricks (in the outer wall), but this is not an acquired taste. If you plaster the internal walls everything should be ok (vapor permeability will further decrease).
Regarding strength, how many floors will your building be? Where do you live? How is your seismic situation?
17.12.2009, 11:16
tomcat_omsk
50 kg/m3 is not enough for walls; you will have to increase the density by tamping down the insulation (without fanaticism), otherwise it will sag noticeably
17.12.2009, 11:40
Eliseev AS
One-story house 10*9m along the external walls, brick gables (half a brick) in the future I plan residential attic, the ceiling is wooden, the location of the house is Nizhny Novgorod region, no earthquakes are expected....
17.12.2009, 11:43
Eliseev AS
I took the density of mineral wool according to the manufacturer’s recommendations; Rockwell generally recommends caviti with a density of 45 units, for layered masonry.
During prolonged rains, will the masonry and insulation not get wet? If so, is this not fatal for mineral wool? And how will all this evaporate from there and affect the insulation?
17.12.2009, 12:28
tomcat_omsk
The mineral wool will be moistened not from rain, but from moisture from the house. It will come from a brick and leave through it in the direction from the house to the outside.
Vapor permeability outside wall no less than internal, facing brick is it ceramic? You need to work through this issue.
More than sufficient stability. If you were building two-story house with reinforced concrete floors, then probably half a brick interior wall it would not be enough, and then a 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 manufacturing plant near us, it’s time to choose silicate
17.12.2009, 13:59
Eliseev AS
The question about the foundation is here, if possible.
I’m designing a foundation based on Sazhin’s book, Bury the Foundations Deep. The soil is fine sand up to 1.4-1.5m, then loam, clay, water at a depth of 0.8 to 1m. 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 cushion of coarse sand 0.5 m high and 1 m wide. I reinforce 3 reinforcement bars at the top and bottom of the tape, diameter 12mm. I reinforce it transversely with wire with a diameter of 4 mm to create cells of 200 * 200 mm. Does this option have a foundation for life??? Freezing depth --- Nizhny Novgorod region On top, as I wrote, there is an armored belt along the entire perimeter of the walls, its height is 300mm.
Is my foundation strong enough???
17.12.2009, 21:52
Andrey teacher
18.12.2009, 08:41
Eliseev AS
Andrey, teacher, I took into account the thickness of the insulation. for the Nizhny Novgorod region. thickness is about 130 mm in layered masonry, I took 150mm, I hope it will be enough? Will the cotton wool not dry at all or will it dry slowly?
And the question is --- if God forbid it rains during the laying and I don’t have time to cover it, will the cotton wool dry out normally?
Based on the foundation, why is it low? one floor, the height of the masonry to the top is 3.60 m, is the foundation not strong enough?