In this article I will consider the issues of ventilation of the inter-wall space and the relationship between this ventilation and insulation. In particular, I would like to understand why the ventilation gap is needed, how it differs from the air gap, what are its functions and whether the gap in the wall can perform a heat-insulating function. This issue has become quite relevant lately and causes a lot of misunderstandings and questions. Here I am giving my private expert opinion based only on personal experience and nothing else.

Denial of responsibility

Having already written the article and rereading it again, I see that the processes occurring during ventilation of the inter-wall space are much more complex and multifaceted than I described. But I decided to leave it as it is, in a simplified form. Especially meticulous citizens, please write comments. We will complicate the description in a working order.

Essence of the problem (subject part)

Let's deal with the subject part and agree on the terms, otherwise it may turn out that we are talking about one thing, but we mean completely opposite things.

This is our main subject. The wall can be homogeneous, for example, brick, or wood, or foam concrete, or cast. But a wall can also consist of several layers. For example, the wall itself (brickwork), a layer of insulation-heat insulator, a layer of external decoration.

Air gap

This is the wall layer. Most often it is technological. It turns out by itself, and without it it is either impossible to build our wall, or it is very difficult to do it. An example is the following additional element walls as a leveling frame.

Suppose we have a newly built wooden house... We want to finish it off. We first apply the rule and make sure the wall is curved. Moreover, if you look at the house from afar, you see a pretty decent house, but when you apply a rule to the wall, you can see that the wall is horribly crooked. Well ... there is nothing you can do! This happens with wooden houses. We align the wall with a frame. As a result, a space filled with air is formed between the wall and the external decoration. Otherwise, without a frame, we will not be able to make a decent exterior finish of our house - the corners will "come apart". As a result, we get an air gap.

Let's remember this important feature the term in question.

Ventilation gap

This is also a layer of the wall. It is similar to an air gap, but it has a purpose. Specifically, it is intended for ventilation. In the context of this article, ventilation is a series of measures designed to draw moisture away from a wall and keep it dry. Can this layer combine the technological properties of the air gap? Yes, maybe this is what, in essence, this article is being written about.

Physics of processes inside the wall Condensation

Why dry the wall? Is she getting wet or what? Yes, it gets wet. And in order for it to get wet, it does not need to be hosed. The temperature difference from daytime heat to nighttime coolness is quite enough. The problem of wetting the wall, all its layers, as a result of moisture condensation, could be irrelevant in a frosty winter, but here the heating of our house comes into play. As a result of the fact that we heat our homes, warm air tends to leave a warm room and again condensation of moisture occurs in the thickness of the wall. Thus, the relevance of drying the wall remains at any time of the year.

Convection

Please pay attention to the fact that the site has good article about the theory of condensation in the walls

Warm air tends to rise up, and cold air tends to go down. And this is very unfortunate, because we, in our apartments and houses, do not live on the ceiling, where warm air collects, but on the floor, where cold air collects. But I seem to be distracted.

It is completely impossible to get rid of convection. And this is also very unfortunate.

But let's consider very useful question... How does convection in a wide gap differ from the same convection in a narrow one? We have already understood that the air in the gap moves in two directions. On a warm surface, it moves up, and down a cold surface. And this is where I want to ask a question. What happens in the middle of our gap? And the answer to this question is rather complicated. I believe that the layer of air directly at the surface moves as quickly as possible. It pulls along the layers of air that are nearby. As far as I understand, this is due to friction. But the friction in the air is rather weak, so the movement of the adjacent layers is much less rapid than the "wall" layers. But there is still a place where the air moving upward comes into contact with the air moving downward. Apparently in this place, where multidirectional flows meet, there is something like a vortex. The lower the flow velocity, the weaker the eddies. With a sufficiently wide gap, these eddies may be completely absent or completely invisible.

But if we have a gap of 20 or 30 mm? Then the swirls can be stronger. These eddies will not only mix the flows, but also inhibit each other. It seems that if you do make an air gap, you should strive to make it thinner. Then two oppositely directed convection flows will interfere with each other. And that's what we need.

Let's look at some fun examples. First example

Suppose we have a wall with an air gap. The gap is deaf. The air in this gap has no connection with the air outside the gap. It is warm on one side of the wall and cold on the other. Ultimately, this means that inner sides in our gap, they differ in temperature in the same way. What's going on in the gap? On a warm surface, the air in the gap rises upward. On the cold it goes down. Since this is one and the same air, a cycle is formed. During this cycle, heat is actively transferred from one surface to another. Moreover, it is active. This means that it is strong. Question. Does our air gap perform a useful function? Looks like no. It looks like he is actively cooling our walls. Is there anything useful about this air gap of ours? No. It looks like there is nothing useful in it. In principle and forever and ever.

Second example.

Suppose we made holes at the top and bottom so that the air in the gap communicates with the outside world. What has changed with us? And the fact that now there is no cycle. Or it is there, but there is both suction and air outlet. Now the air heats up from a warm surface and, possibly partially, flies out (warm), and cold from the street comes in its place from below. Is it good or bad? Is it very different from the first example? At first glance, it gets even worse. The heat goes out into the street.

I will note the following. Yes, now we are heating the atmosphere, and in the first example we heated the skin. How much worse is the first option or better than the second? You know, I think these are about the same options in terms of their harmfulness. This is my intuition tells me, so I, just in case, do not insist on my being right. But in this second example we got one useful function. Now our gap has changed from air to ventilation, that is, we have added the function of the removal humid air, and hence, drying the walls.

Is there convection in the ventilation gap or does the air move in one direction?

Of course have! In the same way, warm air moves up and cold air goes down. It's just that it's not always the same air. And there is also harm from convection. Therefore, the ventilation gap, just like the air gap, does not need to be made wide. We don't need wind in the ventilation gap!

What good is drying a wall?

Above, I called the process of heat transfer in the air gap active. By analogy, I will call the process of heat transfer inside the wall passive. Well, maybe such a classification is not too strict, but the article is mine, and in it I have the right to such disgraceful things. So that's it. A dry wall has significantly less thermal conductivity than a wet wall. As a result, the heat will come more slowly from the inside. warm room to the harmful air gap and to be carried out to the outside will also become less. Trite convection will slow down, since the left surface of our gap will no longer be so warm. The physics of increasing the thermal conductivity of a damp wall is that vapor molecules transfer more energy when they collide with each other and with air molecules than just air molecules when they collide with each other.

How does the wall ventilation process take place?

Well, it's simple. Moisture appears on the surface of the wall. Air moves along the wall and carries moisture away from it. The faster the air moves, the faster the wall dries if it is wet. It's simple. But further it is more interesting.

What speed of wall ventilation do we need? This is one of the key questions of the article. Having answered it, we will understand a lot in the principle of constructing ventilation gaps. Since we are not dealing with water, but with steam, and the latter is most often just warm air, we need to remove this warmest air from the wall. But by removing warm air, we cool the wall. In order not to cool the wall, we need such ventilation, such a speed of air movement, at which steam would be removed, but a lot of heat from the wall would not be taken away. Unfortunately, I cannot say how many cubes per hour should pass along our wall. But I can imagine that not much at all. Some compromise is needed between the benefits of ventilation and the harm from heat removal.

Interim findings

It's time to take stock of some results, without which I would not want to move on.

There is nothing good about an air gap.

Yes indeed. As shown above, a simple air gap does not provide any useful function. This should mean that it should be avoided. But I have always been soft on the phenomenon of an air gap. Why? As always, for a number of reasons. And by the way, I can justify each one.

First, the air gap is a technological phenomenon and it is simply impossible to do without it.

Secondly, if not enough, why should I unnecessarily intimidate honest citizens?

And thirdly, the damage from the air gap does not rank first in the rating of damage to thermal conductivity and construction blunders.

But please remember the following in order to avoid future misunderstandings. The air gap can never, under any circumstances, carry the function of reducing the thermal conductivity of the wall. That is, the air gap cannot make the wall warmer.

And if you really make a gap, then you need to make it narrower, not wider. Then the convection currents will interfere with each other.

The ventilation gap has only one useful function.

This is so and this is a pity. But this single function is extremely, simply vital. Moreover, it is simply impossible without it. In addition, further we will consider options for reducing the harm from air and ventilation gaps while maintaining the positive functions of the latter.

A ventilation gap, unlike an air gap, can improve the thermal conductivity of a wall. But not due to the fact that the air in it has low thermal conductivity, but due to the fact that the main wall or layer of heat insulator becomes drier.

How to reduce the harm from air convection in the ventilation gap?

Obviously, to reduce convection means to prevent it. As we have already found out, we can prevent convection by colliding two convection currents. That is, to make the ventilation gap very narrow. But we can also fill this gap with something that would not stop convection, but would significantly slow down it. What could it be?

Foam concrete or gas silicate? By the way, foam concrete and gas silicate are quite porous and I am ready to believe that there is weak convection in a block of these materials. On the other hand, we have a high wall. It can be 3 and 7 or more meters high. The more distance the air has to travel, the more porous the material should be. Most likely, foam concrete and gas silicate are not suitable.

Moreover, wood, ceramic bricks and so on are not suitable.

Styrofoam? Not! Styrofoam is also not suitable. It is not very easily permeable to water vapor, especially if they have to walk more than three meters.

Bulk materials? Like expanded clay? By the way, here is an interesting proposal. Probably it can work, but expanded clay is too inconvenient to use. Dusty, wakes up and all that.

Low density cotton wool? Yes. I think very low density cotton wool is the leader for our purposes. But cotton wool is not produced in a very thin layer. You can find canvases and slabs at least 5 cm thick.

As practice shows, all this reasoning is good and useful only in theoretical terms. In real life, you can do much easier and more prosaic, which I will write about in a pretentious form in the next section.

The main result, or what, after all, to do in practice?

• When building a private house, you should not specially create air and ventilation gaps. Great use you will not achieve, but you can do harm. If, according to construction technology, you can do without a gap, do not make it.
• If you cannot do without a gap, then you must leave it. But you should not do it wider than circumstances and common sense require.
• If you get an air gap, is it worth bringing (converting) it to a ventilation one? My advice: “Don't bother with it and act according to the circumstances. If it seems that it is better to do it, or you just want to, or this is a principled position, then make a ventilation one, but no - leave an air one. "
• Never, under any circumstances, use materials that are less porous than the materials of the wall itself for external finishing. This applies to roofing material, penoplex and, in some cases, to polystyrene (expanded polystyrene) and also to polyurethane foam. Note if on inner surface the walls are thoroughly vaporized, then non-observance of this point will not bring harm except for cost overruns.
• If you make a wall with external insulation then use cotton wool and do not make any ventilation gaps. Everything will dry out great right through the cotton wool. But in this case, it is nevertheless necessary to provide for air access to the ends of the insulation from below and from above. Or just from above. This is necessary in order for convection, although weak, to be there.
• But what if the house is finished with waterproof material on the outside using technology? For example, a frame house with an outer layer of OSB? In this case, it is necessary either to provide for air access in the space between the walls (from below and above), or provide a vapor barrier inside the room. The last option I like it much more.
• If a vapor barrier was provided for the interior decoration, is it worth making ventilation gaps? No. In this case, the ventilation of the wall is unnecessary, because there is no access to moisture from the room. The ventilation gaps do not provide any additional thermal insulation. They just dry up the wall and that's it.
• Wind protection. I believe that wind protection is unnecessary. The role of wind protection is excellently performed by itself exterior decoration... Lining, siding, tiles and so on. And, again, my personal opinion, the cracks in the lining are not so conducive to blowing heat out to use wind protection. But this opinion is personally mine, it is rather controversial and I do not instruct on it. Again, producers of windscreens also “want to eat”. Of course, I have a justification for this opinion, and I can give it for those interested. But in any case, we must remember that the wind very much cools the walls, and the wind is a very serious cause for concern for those who want to save on heating.

ATTENTION!!!

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have a comment

If there is no clarity, then read the answer to the question of a person who also did not understand everything and asked me to return to the topic.

Hope this article answered many questions and clarified
Dmitry Belkin

Article created on 11.01.2013

Article edited 04/26/2013

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7 years ago

tanya (Builderclub expert) To begin with, I will describe the principle of operation. properly made insulated roof, after which it will be easier to understand the reasons for the appearance of condensation on the vapor barrier - pos. 8. If you look at the picture above - "Insulated roof with slate", then vapor barrier tucked under the insulation in order to retain water vapor from the inside of the room, and thereby protect the insulation from getting wet. For complete tightness, the joints of the vapor barrier are glued with vapor barrier tape. As a result, vapors accumulate under the vapor barrier. In order for them to weather out and not soak the inner lining (for example, gypsum board), a gap of 4 cm is left between the vapor barrier and the inner lining. The gap is ensured by laying the lathing. From above, the insulation is protected from getting wet waterproofing material. If the vapor barrier under the insulation is laid according to all the rules and is ideally sealed, then there will be no vapors in the insulation itself and, accordingly, under the waterproofing, too. But in case the vapor barrier is suddenly damaged during installation or during the operation of the roof, a ventilation gap is made between the waterproofing and the insulation. Because even the slightest, invisible to the eye, damage to the vapor barrier allows water vapor to penetrate into the insulation. Passing through the insulation, vapors accumulate on the inner surface of the waterproofing film. Therefore, if the insulation is laid close to the waterproofing film, then it will get wet from the water vapor accumulated under the waterproofing. To prevent this wetting of the insulation, as well as in order for the vapors to escape, there must be a ventilation gap of 2-4 cm between the waterproofing and the insulation. Now we will analyze the device of your roof. Before you installed the insulation 9, as well as the vapor barrier 11 and the gypsum board 12, water vapor accumulated under the vapor barrier 8, there was free air access from below and they were weathered, so you did not notice them. Up to this point, you essentially had correct design roofs. As soon as you laid the additional insulation 9 close to the existing vapor barrier 8, the water vapor had nowhere else to go except to be absorbed into the insulation. Therefore, these vapors (condensation) have become noticeable to you. A few days later, you laid a vapor barrier 11 under this insulation and sewn up GKL 12. If you laid the lower vapor barrier 11 according to all the rules, namely with an overlap of at least 10 cm canvases and glued all the joints vapor tight tape, then water vapor will not penetrate into the roof structure and will not soak the insulation. But before the installation of this lower vapor barrier 11, the insulation 9 had to dry out. If it does not have time to dry, then there is a high probability of mold formation in the insulation 9. This also threatens the insulation 9 in case of the slightest damage to the lower vapor barrier 11. Because the steam will have nowhere to go except to accumulate under the vapor barrier 8, while soaking the heater and promoting the formation of fungus in it. Therefore, in an amicable way, you need to remove the vapor barrier 8 altogether, and make a ventilation gap of 4 cm between the vapor barrier 11 and the GKL 12, otherwise the GKL will get wet and bloom over time. Now a few words about waterproofing... First, roofing material is not intended for waterproofing pitched roofs, it is a bitumen-containing material and in extreme heat the bitumen will simply drain to the eaves of the roof. In simple words- roofing material will not last long in a pitched roof, it’s hard to even say how much, but I don’t think that more than 2 - 5 years. Second, the waterproofing (roofing material) was not laid correctly. There must be a ventilation gap between it and the insulation, as described above. Considering that the air in the under-roof space moves from the overhang to the ridge, the ventilation gap is provided either due to the fact that the rafters are higher than the layer of insulation laid between them (in your picture, the rafters are just higher), or by laying counter-battens along the rafters. Your waterproofing is laid on the lathing (which, unlike the counter-lattice, lies across the rafters), so all the moisture that will accumulate under the waterproofing will soak the lathing and it will not last long either. Therefore, in an amicable way, the roof also needs to be redone from above: replace the roofing material with waterproofing film, and at the same time lay it on the rafters (if they protrude above the insulation by at least 2 cm) or on a counter-lattice laid along the rafters. Ask clarifying questions. to answer

When insulating walls wooden house many make at least one of the four most insidious mistakes that lead to rapid decay of walls.

It is important to understand that the warm inner space of the house is always saturated with vapors. The vapor is contained in the air exhaled by a person, is formed in a large number in bathrooms, kitchens. Moreover, the higher the air temperature, the large quantity steam he can hold. As the temperature drops, the ability to retain moisture in the air decreases, and the excess falls out in the form of condensation on colder surfaces. It is not difficult to guess what the moisture replenishment of wooden structures will lead to. Therefore, I would like to outline four main mistakes that can lead to a sad result.

Wall insulation from the inside is highly undesirable., since the dew point will move inside the room, which will lead to moisture condensation on a cold wooden surface walls.

But if it's the only one affordable option insulation, it is imperative to take care of the presence of a vapor barrier and two ventilation gaps.

Ideally, the wall cake should look like this:
- interior decoration;
- ventilation gap ~ 30 mm;
- high-quality vapor barrier;
- insulation;
- membrane (waterproofing);
- the second ventilation gap;
- wooden wall.

It should be remembered that the thicker the insulation layer, the smaller the difference between external and internal temperatures will be required for the formation of condensation on a wooden wall. And in order to provide the necessary microclimate between the insulation and the wall, several ventilation holes(vents) with a diameter of 10 mm at a distance of about one meter from each other.
If the house is located in warm regions, and the temperature difference inside and outside the room does not exceed 30-35 ° C, then the second ventilation gap and the membrane can theoretically be removed by placing the insulation directly on the wall. But to say for sure, you need to calculate the position of the dew point at different temperatures.

Using a vapor barrier when insulating outside

Placing a vapor barrier on the outside of the wall is more serious mistake, especially if the walls inside the room are not protected by this very vapor barrier.

The timber absorbs moisture well from the air, and if it is waterproofed on one side, expect trouble.

The correct version of the "pie" for outdoor insulation looks like this:

Interior decoration (9);
- vapor barrier (8);
- wooden wall (6);
- insulation (4);
- waterproofing (3);
- ventilation gap (2);
- exterior decoration (1).

Using insulation with low vapor permeability

The use of insulation with low vapor permeability when insulating walls from the outside, for example, extruded polystyrene foam boards, will be equivalent to placing a vapor barrier on the wall. This kind of material will block moisture on the wooden wall and will promote decay.

Insulation materials with an equivalent or greater vapor permeability than wood are placed on wooden walls. Various mineral wool insulation and ecowool are perfect here.

No ventilation gap between the insulation and the exterior finish

Vapors that have penetrated into the insulation can be effectively removed from it only if there is a vapor-permeable ventilated surface, which is a moisture-proof membrane (waterproofing) with a ventilation gap. If the same siding is placed close to it, the escape of vapors will be very difficult, and moisture will condense either inside the insulation, or, even worse, on a wooden wall with all the ensuing consequences.

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Warming stone wool houses from a bar from the inside with only a vapor barrier Whether to make a vapor barrier from the outside where are the soffits on the attic floor

If you live in the Leningrad Region, then you know that our climate is not the most affectionate. Sunny days are few, the average annual temperature is from 2 to 4.5 degrees Celsius.

Therefore, it is possible to comfortably spend time at the dacha only in the three summer months (even depending on which summer).

But this period can be lengthened if the house is insulated when sheathing with siding.

And in this article, we will figure out together what mistakes are possible when insulating under siding, if it is performed by non-professionals.

The most common mistakes when insulating a house under siding

Let's make it clear right away: professionals do not make these mistakes. Each siding professional has his own individual style, but there are general rules that we all adhere to.

If you notice that the people who insulate your house make these mistakes - chase them in the neck.

It is better to turn to professionals and pay a little more, but get a result that does not have to be redone later.

Let's find out what mistakes can be made when insulating a house under siding.

Rolled insulation instead of slab

This error is caused by the desire to save on materials when insulating a house.

Roll insulation is cheaper than slab, and those who do not understand the technology of insulation are tempted to save money.

Insulate vertical surfaces roll insulation is impossible. It is designed for horizontal surfaces and flat roofs(with a tilt angle of 6: 1 or more flat).

If you insulate the walls with a roll of insulation, then it will very quickly fall to the bottom of the wall, and the top of the wall will give all the heat of your house to the street.

Therefore, when insulating a house under siding, plate insulation should always be used (we usually use mineral wool).

Loose joints between insulation plates

If the plates do not fit tightly to each other, then, in fact, in warm wall a gap will form in your house.

Heat - like water, flows away where it is easier to flow. And the gaps between the insulation plates will be just such places.

That is why log houses are so cold. By the way, we have an excellent one.

Your house will become warmer than before insulation, but some of the heat will still go away. And you, I think, do not need it at all.

Therefore, make sure that people who insulate the walls of your house dock the insulation boards tightly without cracks.

When they cover all this with windproofing, you will not see anything, and your house will be ineffectively insulated under siding.

Loose insulation plates

Some home-grown "craftsmen" will confidently tell you that the slab insulation is quite dense, and you can not fix it to the wall.

And if you believe them, it will be a mistake. Because over time, the insulation of the walls of the house under the siding will settle under its own weight.

The insulation weighs a little, but its bearing capacity is also very low. Therefore, the slab, which is being pressed by a three-meter high pillar of mineral wool, will settle one way or another.

Professionals fix each insulation plate with special "parachutes". This allows the bottom plate to be relieved because each top plate hangs on its own fixture.

Insulation of walls under siding without ventilation

Siding installation technology provides for the creation of a ventilated gap between the siding and the wall of the house.

This space is used to drain condensate into the soffit under the roof.

In the ventilation gap, the ascending air flow blows out the condensate that has settled on the windproof membrane, and the wall remains dry.

If your house is insulated without a vapor barrier, then the absence of a ventilation gap between the insulation and the siding is a guarantee of mold and mildew formation.

In the Leningrad region, with our humidity, this is a matter of a couple of weeks.

When installing siding with house insulation, STK Etalon specialists use a double ventilated frame, which ensures condensate discharge into the roof overhang and reliable ventilation of the insulation under the siding.

Cold bridges when insulating walls under siding

Most shabashniki, "wild brigades" and even some firms mount the siding frame on "kolobashki".

A kolobashka is a piece of wood between the wall and the frame, to which the siding is then attached. She aligns the frame in a vertical plane so that the wall becomes even after sheathing with siding.

The kolobashka is screwed to the wall, and a block of 50x50 mm is screwed to it, between which the insulation is laid.

This is the most common method of insulating walls under siding among non-professionals.

But the question arises: what prevents the heat from leaving your home in those places where the frame passes?

Nothing gets in the way.

Heat leaks out through these gaps in the insulation. It turns out as in the case of the gaps between the insulation plates, only much worse.

Because the slots under the frame are much wider (along the width of the bar).

This problem is being solved fundamentally different approach for house insulation under siding. We at STK Etalon have found this solution and we insulate houses under siding without cold bridges.

If you contact STK Etalon, you can be sure that there will be no heat loss through the cracks in your house.

In all honesty, it is better not to insulate houses made of solid wood at all. High-quality massive logs and beams, being preserved in their natural form, provide an optimal microclimate in the house. Wood, unlike most others wall materials, "Breathes", this is one of its main advantages. However, in the case of insufficient thickness of wooden walls, or if the house has already stood for many years and the logs need protection from external influences, external insulation and cladding are justified measures, helping to reduce heating costs and prolong the life of decaying wood. Most practical material for the exterior cladding of a wooden house - vinyl siding. It is inexpensive, its service life is half a century or more, it is easy to install, and it can be repaired without any problems. The siding house looks neat. Let's tell you how it should be correct insulation wooden house for siding.

To improve thermal insulation without worsening the microclimate and without harming the structure, you need to understand the specifics of the construction and operation of a wooden house. Let's start with theory: a little about woodworking and a little building physics.

Wood moisture and harmful fungi

We all know how quickly wood that is constantly in a wet state is attacked by molds. The loss of strength of the material occurs in a matter of months, and in a year or two a log, in the thickness of which favorable conditions for the vital functions of mushrooms, it can turn into dust. The main condition for mold growth is sufficient moisture. Accordingly, in order to preserve a wooden house for many years, its walls and other structures must be protected from waterlogging. Absolute moisture (the ratio of the mass of water to the weight of absolutely dry wood) of freshly cut forest conifers reaches 90%, a log house before installation - 25-35%, a wooden house, which has stood during the year under normal conditions - 10-20%, depending on the season. At the same time, fungal infection of wood begins to develop from a moisture level of 22%, which is only slightly higher than the natural state of a log house. By the way, the same conditions are suitable for the woodworm beetle to settle in the logs.

It is important to know: in no case should the wood become waterlogged - the main reason for its destruction.

Waterlogging of the tree leads to its rotting

Where does moisture get into the tree?

It is believed that moisture enters the walls of a wooden house from the outside with slanting rain, fog and snow. Precipitation does moisturize the walls. But wet weather does not last so long, the sun and especially the wind contribute to the rapid removal of excess moisture. An attentive reader will say: the average annual air humidity outside is 78% (data for the Moscow region), and in the house it fluctuates between 40-70% - this means that there is more moisture outside and it must penetrate from the outside to the inside.

But actually it is not. The fact is that climatologists operate with relative humidity, this is the ratio of the proportion of water vapor to the maximum possible, taking into account the temperature. And the colder the air, the less moisture it can contain. To understand the real moisture content in the air, the values ​​of absolute humidity are used in construction physics. In summer, when the temperature is about the same outside and in the house, the humidity is similar. But in winter and in the off-season, the picture is completely different. For example, at an outside temperature of -20 ºС and a relative humidity of 80% of the outside air, the absolute value will be 0.6 g / m3, and inside the house at 20 ºС and a relative humidity of 60%, the absolute value will be 10.4 g / m3. Accordingly, the actual moisture content in the air inside the house is 17 times higher. It is not surprising that wood, like a pump, absorbs moisture from the inside and gives it out through micropores and joints between logs filled with flax, moss, jute or other "breathing" inter-crown insulation.

It is important to know: most of the year, with the exception of the warm period, water vapor penetrates into the wood from the inside of the house and tends to escape from the outside, the more it is, the colder it is outside and the warmer it is in the house.

Ventilation - vapor barrier - wind protection

We found that a prerequisite for maintaining a log house and a healthy microclimate in it is that the insulation of the walls of a wooden house for siding should not impede the free exit of water vapor.

Modern designs in wooden (and not only) housing construction, they imply the widespread use of vapor barrier and windproof films. The first ones are absolutely sealed, they do not allow air or steam to pass through. The latter repel water droplets, but do not impede the penetration of water vapor. V frame houses the wall is closed from the inside with a vapor barrier, thereby excluding the penetration of moisture from the premises into the insulation and wooden structures... Outside, the walls are "wrapped" with wind insulation: it counteracts the blowing of the insulation, does not allow water droplets from the outside to get inside (condensation may fall on the inner surface of the siding), while water vapor freely escapes outside. Since the insulation is closed finishing material(in our case, this is siding), there must be a ventilation gap between the insulation and the finish so that excess moisture can leave the wall structure.

It is important to know: the ventilation gap is an obligatory element of the construction of insulation for siding and other cladding materials.

Many shabashniki, Internet sources, managers of construction companies and even professional builders argue that the same should be done when insulating a house made of solid wood. That is, the first layer, along the logs, stretches the vapor barrier, then the insulation, on top - the wind protection, the ventilation gap and finishing material, siding in our case, completes the structure. At the same time, it is not taken into account that moisture tending outward will hit the vapor barrier, the humidity in the area adjacent to the vapor barrier will increase, and condensation will fall out when the dew point occurs. Conditions will be created for the germination of fungal spores, and from the inside we will not notice the beginning of the destruction of wood for a long time.

Windproof film (diffusion membrane) has many micro-holes, due to which steam passes through, at the same time, water droplets roll off the material

The eternal question: what to do?

We support the point of view of those specialists in construction physics and technologists working in the field of wooden housing construction that vapor barrier is not needed when insulating a wooden house. The only case when placing a vapor barrier between load-bearing wall and insulation can be justified - the house (dacha) is used seasonally, it is rarely heated in winter, or the rooms are kept at a minimum temperature and they are well ventilated. With this operating mode, the temperature difference and, accordingly, the absolute humidity outside and inside is low. For a home where people live permanently, there are internal sources of moisture (breathing of people, steam from kitchen pots and showers, moisture from watering house plants), vapor barrier is more likely to be harmful than beneficial. It is not always possible to do without a film, especially if the logs are uneven, and the insulation is too soft or even backfilled. In this case, wind insulation (with the highest vapor transmission value), building board, craft paper, and even a spunbond that has served its purpose in the garden can be laid as a limiting material between the wall and the insulation structure for siding.

As a counterargument to the lack of vapor barrier, supporters of its placement say that the insulation unprotected from steam penetration will be moistened and its thermal performance will deteriorate. Alas, they are right. But the ventilation gap facilitates the removal of moisture, and a relatively small (5-15%) drop in heat-shielding properties is a forced victim in the struggle for the durability of the building.

It is important to know: vapor barrier is not needed when insulating a wooden house in which people live all year round.

This cannot be done if the house is inhabited all year round! Walls "wrapped" in glassine will become waterlogged and become defenseless against mold damage

Material for the frame and the "correct" insulation

For the frame, use only flat wooden blocks, preferably antiseptic. Steel profiles, which are recommended to be used by "sofa" masters, freeze, moreover, condensation appears on them, which does not benefit either the insulation or the walls.

The cross-section of the bars should correspond to the thickness of the insulation, for mineral wool it is, as a rule, 5 cm. Accordingly, the bars are 5x5 or 4x5 cm.The recommended size of the ventilation gap is 4-5 cm, therefore, for the counter-batten that provides the required distance between the insulation and the siding, you can use the same stuff.

The insulation must be vapor permeable and lightweight. The most affordable - semi-hard mineral wool mats, soft rolls should not be used, they will shrink in the wall over time. Ideal for a wooden house, environmentally friendly, very durable, but alas, not cheap material - linen and hemp mats. Between the wall and the windscreen, you can fill in cellulose wool, wool waste. Again, the main thing for insulation is vapor permeability. Mineral wool can be placed in two layers (10 cm) or one (5 cm). What should be the general layer of insulation, decide on the basis of climatic conditions and the thickness of the existing walls.

Linen mats have much longer fibers than rock wool, so they hold their shape better and longer

Work technology

The technology of insulating a wooden house for siding is quite simple, any "handy" man can do such work.

• The distance between the bars should not exceed 60 cm, it is better that it be equal to the width of the insulation, for mineral wool it is 50 cm.
• We recommend fixing the first level of blocks vertically. The second, if the insulation is laid in two layers, horizontally. The counter rail to which the siding will be directly attached is vertically.

A frame for insulating a log house with mineral wool in two layers.

• On uneven walls the bars are conveniently fastened using perforated plasterboard straps. Time consuming, but preferable from the point of view of heating engineering will be traditional method: Adjust the distance from the wall by placing wooden bosses. The screws will hold the frame better than nails.

Options for the frame and insulation for siding.

• If the mineral wool mats are too soft, we recommend installing one or two horizontal lintels in each vertical section, this will reduce the subsidence of the material.
• Sewing the frame and filling the gaps between its elements with insulation, they attach the windscreen, and on top of it there is a counter-rail.

The frame is filled with insulation, the next stage is wind protection

• Final work - siding of a wooden house.

"Correct" construction of wall insulation for siding with a double layer of mineral wool.

Free air flow must be ensured in the ventilated gap. To do this, in the outer sheathing at the bottom and at the top of the wall, gaps are left (closed with a mesh from mice and insects) or inserted into the siding panels of the lattice.

It is important to know: ventilation holes should be located at the bottom and top of the wall cladding.

Not everyone has the ability and the necessary skills to do this kind of work. If you are not confident in your abilities, it is better to entrust the insulation own home and cladding it with siding experienced craftsmen.

Video: a wooden house - how to sheathe and how to insulate

Cold bridges called the sections of the building envelope through which the largest occur, which leads to a number of negative consequences... Today we will talk about how to prevent the appearance of cold bridges in an insulated (attic) structure.

Cold bridges in insulated construction pitched roof cause many problems:

1. First, they reduce the efficiency of the building's thermal protection, which leads to an increase in energy consumption, which, in turn, results in an increase in the cost of operating the house.
2. Secondly, in the cold season, condensation accumulates in the freezing zone, which leads to wetting and gradual damage used to insulate the roof (which also worsens the thermal protection of the building).
3. Thirdly, due to condensation, wooden roof structures can become moldy, rot and eventually collapse. Condensation often deforms the finish.
4. Finally, fourthly, the condensate in winter can freeze and break the cracks and gaps that it filled.

Warming errors

What causes cold bridges? According to experts, in most cases this is due to errors in the construction of the insulating layer of the roofing "pie". Recall that the most common mansard roof erection technology involves the insulation of the slopes (which are at the same time the walls of the attic) with fibrous materials: plates and - less often - mats based on or.

Another node dangerous in terms of freezing is the junction of the roof with the gable of the building.

Valery Nesterov, general manager Dörken company:
“There is a very high probability of freezing at the junction of the roof with the gable of the building. To prevent it, in the West, there are special U-shaped elements made of extruded polystyrene foam, which are "put on" on the gable wall. On our market there are special diffusion hydro-windproof membranes with an integrated layer of insulation with a thickness of 30 mm made of non-woven material: they can also protect this area from freezing. However, the traditional solution is to fill the space between the extreme rafter beam and the gable wall (usually about 50 mm), the gap between the upper surface of the wall and the waterproofing film, and also lay the insulation along the upper edge of the wall. As a result, a continuous thermal insulation contour is created that covers the pediment and transfers the dew point inside the wall, thereby eliminating the possibility of condensation falling out in the thickness of the roofing insulation. "

1. The first difficulty lies in the fact that often on the entire upper part of the inclined pediment wall there are ledges formed due to masonry (from bricks, blocks). To level the wall, often use "cold" cement-sand mortar, which becomes a cold bridge. It is better to use a "warm" solution with the addition instead. Or fill irregularities with thermal insulation.
2. The second difficulty is to insulate this place with high quality. It is necessary to leave a distance of at least 50 mm between the rafter foot closest to the gable and the gable wall, filling this space with thermal insulation. In addition, it is desirable that the upper plane of the wall be 50 mm lower than the upper plane of the rafter legs, and then the insulation is also laid on top of the wall at the height of the legs, ensuring its tight fit to the insulation running along the rafter. If possible, the insulation is also mounted along its edge from the street side - with a layer equal to the thickness of the insulation on the roof slope.

Here you can use both fibrous thermal insulation and materials from. It is preferable to put the insulation on top of the pediment even before laying the hydro-windproof membrane - for the same reasons that we talked about just above.

Freezing through the rafters

Problematic are also the joints of the wooden elements of the roof (located between its warm and cold zones), as well as composite rafter legs, made by combining two beams into one. Cold bridges can appear here for several reasons: due to the loose fit of the elements to each other (caused, among other things, by their curvature), due to precipitation rafter system etc. To avoid this, the joints should be laid with sealing materials, for example, synthetic winterizer or foamed polyethylene. However, a number of roofers believe that the latter reduces the reliability of the connection of wooden elements. If you have to seal the joints after installing the rafters, then you can use specialized sealants, PSUL (pre-compressed self-expanding sealing tapes) or polyurethane foam however it is not cheap and quite time consuming. This solution has one more significant disadvantage: the foam, being inelastic, can collapse when a wooden structure settles.

An effective way to prevent heat loss- to create an additional layer of roof insulation covering possible cold bridges.

On the picture:
1. On roofs of complex configuration, you inevitably have to cut the insulation slabs to fit them into the space between the rafters.
2. Fastening the vapor barrier film to the rafter leg.
3. Installation of the undercut slab in the ridge area.
4. The cracks in the insulation layer are caulked with fragments of the same heat-insulating material.

Freezing is also possible at the points of exit through the wall to the Mauerlat street, ridge or intermediate girders, on which the outgoing rafters rest. To prevent the movement of cold air here, you must first of all qualitatively seal the gaps between the beam and the wall, and also do not forget to seal (glue with glue or special tape) the places where the vapor barrier and hydro-windproof films bypass the beam.

The skylight area is another roof area where cold bridges can occur.

This often happens due to the absence or insufficient thickness of the insulation layer around the perimeter. window frame and along the slopes. To prevent freezing, it is necessary to leave a gap of 20-30 mm around the frame, filling it with thermal insulation, which should be brought up to the roof insulation contour.

For ease of installation, window manufacturers offer ready-made kits for thermal insulation around the frame perimeter(for example, foamed polyethylene). Some firms produce windows with thermal insulation already provided on the frame. Note that window manufacturers categorically prohibit insulating the frame with polyurethane foam.

Marina Prozarovskaya, Chief Engineer Velux:
“Among the reasons for freezing in the skylight area is the lack of thermal insulation around the perimeter of the window box. This is often caused by too small mounting clearances between the frame and the rafters. Leave a gap of at least 30 mm around the frame perimeter, installing around it either a ready-made thermal insulation loop made of foamed polyethylene or a fibrous insulation. Foam can not be used for these purposes: it is inelastic and crumbles under the influence of periodic loads (roof draft, snow, wind load), as a result of which cracks appear in the thermal insulation. If the width of the window is equal to or greater than the width of the rafter opening, then in order to ensure the necessary mounting clearances around the frame, you will have to adjust the rafters, keeping them bearing capacity... Sometimes this can be done without special calculation according to the schemes specified in the instructions for installing windows. This usually involves the installation of an additional beam, the section of which coincides with the section of the rafter leg. "

In most cases, cold bridges are the result of condensation, leading to wetting of the insulation in the window area. There can be many reasons for its formation. In particular, the non-glued joints of the vapor barrier film with the window frame: water vapor has a high penetrating ability, and getting into cold zone, condenses. Often, condensation is a consequence of certain errors in the construction of the ventilation system of the roof structure.

For example, there are no conditions for air flow or its extraction, there is no counter-grill that forms a ventilation gap, or its height is insufficient to provide the necessary air movement under. However, unsealed joints and abutments of both under-roofing films, as well as insufficient ventilation of the under-roof space are errors that lead to condensation and freezing. not only in the window area, but also throughout the roof... It's just that in the window area it becomes noticeable first of all. Moreover, many mistakes cannot be corrected during the operation of the building without complete dismantling of the roof.

According to the calculations of specialists, in the conditions of the Moscow region every 5 cm of thermal insulation saves an average of 18 rubles on heating. for 1 sq. m roof area per year.

A few more words about roof window... Problems arise and if the drain gutter is installed incorrectly over the window opening. This gutter drains water (leaks, condensation) from the window, which flows down the hydro-windproof membrane to the window. Before laying it, the membrane is cut, and then its edge is inserted into it, securing it with a special clamp, after which the upper edge of the waterproofing window apron is brought under the gutter. If the gutter installation technology is not followed, leaks into the insulation are possible with all the ensuing consequences.

Certain pass-through elements - pipes, antennas, flagpoles, etc., become heat-conducting inclusions in the roof structure. Therefore, they must be properly insulated and hermetically joined with vapor barrier and hydro-windproof films.

To minimize freezing through the walls, experts advise creating an additional heat-insulating belt with a height of about 250 mm over the standard insulation contour (that is, above the roof). To protect against precipitation, the belt must be covered with one or another apron.

Ekaterina Kolotushkina, product manager at Saint-Gobain CIS:
“To make the attic as comfortable as possible for living and to ensure the durability of the roof structure allows the creation of an additional insulation contour. The fact is that wooden load-bearing elements the roofs are to some extent cold bridges. In addition, according to calculations, the thermal insulation layer in the central part of Russia should be 200 mm, however, the thickness of the most popular beams on the market used for the construction of rafters is 150 mm (and the insulation is placed in the inter-rafter space). Thus, it makes sense to create an additional thermal insulation layer that will provide the required insulation thickness and block the cold bridges that go through the rafters. This layer can be placed above and below the rafters by placing the insulation between the bars nailed across the rafters. Thermal insulation above the rafters is preferable, because in this case they do not freeze. "

Additional layer of insulation

Despite all the efforts of roofers, heat loss is inevitable in those parts of the roof, where the area of ​​the internal "warm" surface is less than the area of ​​the external "cold". These are mainly the corners of hip or hip roofs (in the zone of convergence of the ridge and eaves), the places where the slope adjoins to the pediment, etc. In addition, wooden rafter legs are also to a certain extent cold bridges. And it is difficult to insulate complex sections of the roof with high quality, where filigree pruning (valleys, ridges, abutments) is required. Finally, the thickness of the heat-insulating layer in central Russia should be, according to SNiP 23-02-2003 " Thermal protection buildings ", not less than 200 mm... While the most popular material for the construction of rafters is still the cross-section of 150 × 50 mm, which implies the thickness of the inter-rafter insulation layer - 150 mm. All these factors explain the need to create additional contour of roof insulation.

It can be mounted over the rafters and under them... In the first case:

1. Wooden bars of the required section are stuffed across the rafters, between which insulation plates are installed.
2. A hydro-windproof membrane is laid on top of the bars.
3. A counter-lattice, lathing or solid flooring is fixed on it, and roofing material is placed on them.

This option is effective in terms of thermal protection, because the entire rafter structure will be in the "warm" zone. However, it is not without its drawbacks:

• Fixing the roof to the base is less reliable due to the additional wooden substructure.
• In addition, when installing hydro-wind protection, the joints of the canvases may be on the insulation (and not on wooden base), and the installers will push the film, moving along the roof.

That's why optimal technology is an additional insulation under the rafters... In this case, from the side of the room, transverse bars are attached to the rafters, thermal insulation is laid between them, and then it is closed with the attic finishing material.

There is another effective, but so far almost unused method of insulation - installation on top of the rafters solid flooring, on which slabs of high density stone fiber, wood fiber, polyurethane foam are laid. The roof is mounted directly on the slabs.



1. Rafter leg.
2. Additional insulation circuit.
3. Cross bar.
4. Finishing of the attic.

Let's note one more point. In the fight against freezing of the roof will help modern methods cold bridges detection- examination with a thermal imager or hot-wire anemometer. The cost of purchasing or renting these devices is less than the cost of repairing a frozen roof.

In most cases, it is more profitable for a private developer not to buy a thermal imaging camera, but to contact a specialized company that deals with the thermographic examination of buildings.

Types of heaters for a pitched roof

To insulate a pitched roof, plates (or mats) made of stone or glass fibers are most often used.

• In our market, materials from stone fiber are represented by Rockwool (Denmark), Paroc (Finland), Nobasil (Slovakia), TechnoNikol, Isoroc, Knauf (all - Russia), etc.
• Glass fiber heaters are offered by Isover (France), Ursa (Spain), etc.

Extruded polystyrene foam or polyurethane foam materials, although they have very good thermal insulation properties, are not fireproof: expanded polystyrene belongs to the group of highly combustible materials (G4), and polyurethane foam belongs to the group of moderately or slightly combustible (G2-G3). At the same time, fiber insulation is non-combustible (NG).

The material was prepared by Alexander Levenko.

Consider several typical mistakes, which are allowed when insulating buildings by private developers. What needs to be done to make the house insulation reliable, durable, and comply with the heat saving standards?

Now in private housing construction, three-layer walls are especially popular, in which the inner and outer (front) walls are laid out of bricks or similar small-piece material, and between them there is a layer of insulation. In this case, the same error is repeated.

Poor insulation

The fact is that the insulation in a three-layer wall is difficult to replace without destroying ... the entire wall. Including the inner layer, because it contains connections with the outer layer, and in order to renew them after the destruction of the outer layer ...

In general, if the insulation layer becomes unusable, then the owners will simply be left with cold walls and with the prospect of expensive repairs.

When building expensive, durable three-layer brick walls usually everyone wants to use the cheapest foam as a heat insulator. And this material is not durable, strives to crumble over time into individual granules, and they lose their integrity, voids arise. In addition, mice eat polystyrene, and they gladly settle in it - after all, it is warm there.

If the foam is not closed completely durable plastering layer, as in the system " Wet facade", Then the rodents will get to him, and this is a common phenomenon with three-layer walls, then foam insulation will be incapacitated for the season.

But this is not so bad. Styrofoam (expanded polystyrene foam) is able to moisten and from this rapidly disintegrate, mold and mildew grows on it, walls are moistened, and thermal insulation properties are significantly lost.

This can happen if you just wrap this material between two brickwork, which is often the case. In this case, the vapor permeability of various layers of the wall becomes close (the vapor permeability coefficient of the foam is 0.05 mg / (m h Pa)), or outer layer made of dense clinker bricks are more resistant to steam movement than the inner layers. Moisture will accumulate inside the wall in cold weather with the ensuing consequences….
So how to control the movement of steam?

Not at ease with steam movement

If you do not correctly control the movement of steam, then any insulated structure consisting of two or more layers will get wet, it will collapse, heat loss will increase much. If you use expensive dense mineral wool in a three-layer wall in the same way as foam in the previous example, then the consequences will be even worse (wetter), because cotton wool accumulates water much better.

And the way out is in the correct use of heaters in a three-layer construction. There, it is preferable to use dense (from 60 kg / m3) mineral wool that does not lose its shape over time, durable, like the brick itself, which rodents and other living creatures "hate".

But it must be constantly ventilated by analogy with the ventilated facade system, for which a vent is left. gap and holes are made in the outer layer. Cotton wool is either covered with a windproof membrane, or denser samples are used - 80 - 180 kg m 3. having their own high resistance to air movement.

You can also use extruded polystyrene foam, while the wall thickness will decrease, since no ventilation is needed. the gap and thickness of the insulation will be less than 25 percent. But the guarantee against rodent access to the inside of the wall must be iron.


Those. sand-cement-concrete lining must cover internal insulation from all sides and be especially reliable. And extruded polystyrene foam is always at odds with steam, since it simply does not let it pass through and does not accumulate water. As a result, the layers are separated in pairs, the wall is dry and does not breathe.

Sprayed polyurethane foam is also close to such properties, but only of the highest density. So you can blow into the wall…. But the option with ventilated "eternal" mineral wool looks still preferable.

Polyfoam is a favorite insulation

Another inconsistency with steam is the foam coating of lightweight porous materials. Then the rule is simply violated - the more vapor-permeable layer must be outside.

Foam is usually used to insulate two popular surfaces - wooden walls and foam concrete blocks... In any case, the layer, which is more difficult for the movement of steam, does its job - the bearing layers get wet, become unusable, the tree sprays rapidly at the point of contact with synthetics. Of course, it is possible and necessary to apply foam, but only where it belongs.

We neglect the superdiffusion membrane - it is expensive

Instead of a superdiffusion membrane (vapor permeable from 1700 g / m2 per day) of the required quality (sometimes especially heat-resistant is required), some developers try to cover the mineral wool in the roof or on the wall with perforated film, or even just a piece of polyethylene, without delving into the essence of the issue. As a result, steam does not escape from the insulation layer, the insulation gets wet along with the structure and everything collapses.

It should be noted that according to recent studies, hydrophobized mineral wool with a density of 80 kg / m3 for a wind zone up to 5 and 180 kg / m3 for any wind zone can be used in the system curtain facade and in a roof without a membrane, since their own air permeability is very low.

Those. air does not actually go through such a heater and there is no convection heat removal from the insulation layer. Of course, a snug fit must be ensured mineral wool boards to structures and the absence of gaps between them.

But it should be borne in mind that the membrane on the roof and on the wall is sometimes provided for by the project as an additional protection against water leaks, then without it it is not possible.

All the other way around

In conclusion, the case when it never gets worse - the insulation is attached to the enclosing structures from the inside of the building. Because it seems to be faster and cheaper. Insulation from the inside is an extreme case and a necessary measure. In principle, it can be done, but only by certain rules and it still has a lot of overhead.

So let's insulate according to the rules - outside, with insulation provided by the project, required thickness, with the provision of ventilation if necessary, and with the required quality of the materials used.