Do I need a gap between the vapor barrier and the insulation on the walls. Insulation of a wooden house: typical mistakes Insulation of walls under siding without a ventilation gap
In this article I will consider the issues of ventilation of the interwall space and the connection between this ventilation and insulation. In particular, I would like to understand why ventilation gap how it differs from air, what are its functions and whether the gap in the wall can perform a heat-insulating function. This question becomes quite relevant in Lately and raises a lot of misunderstandings and questions. Here I give my private expert opinion, based only on personal experience and on nothing else.
Denial of responsibility
Having already written the article and re-reading it once again, I see that the processes occurring during the 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 version. Particularly meticulous citizens, please write comments. We will complicate the description in working order.
The essence of the problem (subjective part)
Let's deal with the subject matter and agree on 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 the wall can also consist of several layers. For example, the wall itself (brickwork), a layer of insulation-heat insulator, a layer of exterior finish.
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. As an example, such 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 that the wall is curved. Moreover, if you look at the house from a distance, you see a quite decent house, but when you apply a rule to the wall, it becomes clear that the wall is terribly crooked. Well ... there's nothing to be done! 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 exterior finish. Otherwise, without a frame, it will not be possible to make a decent exterior finish of our house - the corners will “disperse”. As a result, we get an air gap.
Let's remember this important feature the term in question.
ventilation gap
This is also a wall layer. It looks like an air gap, but it has a purpose. Specifically, it is designed 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? Let it get wet. And in order for it to get wet, it does not need to be watered from a hose. The temperature difference from the heat of the day to the coolness of the night is enough. The problem of getting the wall, all its layers, wet 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 houses, the warm air tends to leave the warm room and moisture condenses again 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 a good article about the theory of condensate in the walls
Warm air tends to rise up and cold air sinks down. And this is very unfortunate, since we, in our apartments and houses, do not live on the ceiling, where warm air is collected, but on the floor, where cold air is collected. But I seem to have digressed.
It is completely impossible to get rid of convection. And this is also very unfortunate.
Now let's look at a 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. It moves up on a warm surface and down on a cold surface. And this is where I want to ask a question. And 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 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 neighboring layers is much less fast than the "wall" ones. But there is still a place where the air moving up comes into contact with the air moving down. Apparently in this place, where multidirectional flows meet, something like turbulence occurs. The eddies are the weaker, the lower the flow velocity. With a sufficiently wide gap, these swirls may be completely absent or completely invisible.
But if the gap we have is 20 or 30 mm? Then the twists can be stronger. These turbulences will not only mix the flows, but also slow each other down. It seems that if you make an air gap, then you should strive to make it thinner. Then two differently 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. Warm on one side, cold on the other. Ultimately, this means that inner sides in our gap in the same way they differ in temperature. What's going on in the gap? On a warm surface, the air in the gap rises. It goes down in the cold. Since it is the same air, a cycle is formed. During this cycle, heat is actively transferred from one surface to another. And actively. It means strong. Question. Does our air gap perform a useful function? Looks like no. It looks like he actively cools the walls for us. Is there anything useful in this air gap of ours? No. There doesn't seem to be anything useful in it. Basically, forever.
Second example. 
Suppose we made holes at the top and bottom so that the air in the gap communicated with the outside world. What have we changed? And the fact that now there is no cycle. Or it is, but there is both a suction and an air outlet. Now the air is heated from a warm surface and, possibly, partially flies out (warm), and cold from the street comes in its place from below. Is this good or bad? Is it very different from the first example? At first glance, it gets even worse. Heat goes out.
I will note the following. Yes, now we are heating the atmosphere, and in the first example we were heating 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 telling me, so I, just in case, do not insist on my being right. But on the other hand, in this second example, we got one useful function. Now our gap has become from air ventilation, that is, we have added the removal function humid air, which means drying the walls.
Is there convection in the ventilation gap or is there air moving in one direction?
Of course have! Similarly, warm air moves up while cold air moves down. It's just 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's good about 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 my article, and in it I have the right to such outrages. So. A dry wall has a much lower thermal conductivity than a wet one. As a result, the heat will slowly reach from the inside. warm room to the harmful air gap and will also become less carried out. Tritely, 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 colliding with each other and with air molecules than just air molecules when colliding with each other.
How is the process of ventilation of the wall?
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 out if it is wet. It's simple. But more interesting.
What wall ventilation rate do we need? This is one of the key points of the article. By answering 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 very warm 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, and a lot of heat would not be taken away from the wall. Unfortunately, I cannot say how many cubes per hour should pass our wall. But I can imagine that not much at all. Some compromise is needed between the benefits of ventilation and the harm of heat removal.
Intermediate conclusions
It's time to sum up some results, without which I would not want to move on.
There is nothing good in the air gap.
Yes indeed. As shown above, a simple air gap does not provide any useful functionality. This should mean that it should be avoided. But I have always been soft on such a phenomenon as an air gap. Why? As always for a number of reasons. And, by the way, each I can justify.
Firstly, the air gap is a technological phenomenon and it is simply impossible to do without it.
Secondly, if I can't do it, then why should I unnecessarily intimidate honest citizens?
And thirdly, the damage from the air gap does not take first place in the rating of damage to thermal conductivity and construction mistakes.
But please remember the following, in order to avoid future misunderstandings. The air gap can never and under no 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 already 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.
It is and it is very unfortunate. But this single function is extremely, simply vital. Moreover, without it it is simply impossible. In addition, further we will consider options for reducing the harm from air and ventilation gaps while maintaining the positive functions of the latter.
The ventilation gap, unlike the air gap, can improve the thermal conductivity of the wall. But not due to the fact that the air in it has a low thermal conductivity, but due to the fact that the main wall or the heat insulator layer 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 it down. 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 needs to travel, the more porous the material we need to have. Most likely, foam concrete and gas silicate are not suitable.
Moreover, wood, ceramic bricks and so on are not suitable.
Styrofoam? Not! Styrofoam doesn't work either. It is not too easily permeable to water vapor, especially if they have to travel more than three meters.
Bulk materials? Like expanded clay? Here's an interesting suggestion. It probably can work, but expanded clay is too inconvenient to use. Dust, wakes up and all that.
Wool low density? Yes. I think that wool of very low density is the leader for our purposes. But cotton wool is not produced in a very thin layer. You can find canvases and plates at least 5 cm thick.
As practice shows, all these arguments are good and useful only in theoretical terms. V real life you can do much simpler 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 personal home, you should not specifically create air and ventilation gaps. You will not achieve great benefits, but you can cause harm. If the construction technology can do without a gap - do not do it.
- If you can’t do without a gap, then you need to leave it. But you should not make it wider than circumstances and common sense require.
- If you have an air gap, is it worth bringing (turning) it to a ventilation one? My advice: “Don't worry about 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 if not, leave an air one.
- Never, under any circumstances, use materials that are less porous than the materials of the wall itself for a durable exterior finish. This applies to roofing felt, foam plastic and, in some cases, to foam plastic (expanded polystyrene) and also to polyurethane foam. Note that if a thorough vapor barrier is arranged on the inner surface of the walls, then failure to comply with this paragraph will not bring harm, except for cost overruns.
- If you are making a wall with external insulation, then use cotton wool and do not make any ventilation gaps. Everything will dry out wonderfully right through the cotton wool. But in this case, it is still necessary to provide air access to the ends of the insulation from below and from above. Or just above. This is necessary in order for convection, although weak, to exist.
- But what if the house is finished with waterproof material on the outside according to technology? For example, a frame-panel house with an outer layer of OSB? In this case, it is necessary either to provide for air access to the inter-wall space (from below and from above), or to provide a vapor barrier inside the room. I like the last option much better.
- If a vapor barrier was provided during the interior decoration, is it worth making ventilation gaps? No. In this case, ventilation of the wall is unnecessary, because there is no access to moisture from the room. Ventilation gaps do not provide any additional thermal insulation. They just dry the wall and that's it.
- Wind protection. I don't think wind protection is needed. The role of wind protection is wonderfully performed by the exterior trim itself. Lining, siding, tiles and so on. Moreover, again, my personal opinion, the slots in the lining are not so conducive to blowing out heat to use wind protection. But this is my personal opinion, it is rather controversial and I do not instruct on it. Again, manufacturers of windscreens also "want to eat." Of course, I have the justification for this opinion, and I can give it for those who are interested. But in any case, we must remember that the wind cools the walls very much, and the wind is a very serious cause for concern for those who want to save on heating.
ATTENTION!!!
To this article
there is a comment
If there is no clarity, then read the answer to the question of a person who also did not understand everything and he asked me to return to the topic.
I hope that this article has answered many questions and brought clarity
Dmitry Belkin
Article created 01/11/2013
Article edited 04/26/2013
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| 7 years ago | tanya (expert Builderclub) 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 condensate on the vapor barrier - pos.8. If you look at the figure above - "Insulated roof with slate", then vapor barrier it is laid 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 vapor barrier tape. As a result, vapors accumulate under the vapor barrier. In order for them to weather and not soak the inner lining (for example, gypsum plasterboard), a gap of 4 cm is left between the vapor barrier and the inner lining. The gap is provided by laying the crate. On top, the insulation is protected from getting wet waterproofing material. If the vapor barrier under the insulation is laid in accordance with all the rules and is perfectly hermetic, then there will be no vapor 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, not noticeable 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, it will get wet from water vapor accumulated under the waterproofing. To prevent this wetting of the insulation, as well as for the vapors to erode, there should be a ventilation gap of 2-4 cm between the waterproofing and the insulation. Now let's take a look at your roof. Before you laid insulation 9, as well as vapor barrier 11 and GKL 12, water vapor accumulated under 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 basically 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 but to be absorbed into the insulation. Therefore, these vapors (condensate) have become noticeable to you. A few days later, you laid vapor barrier 11 under this insulation and sewed up GKL 12. If you laid the lower vapor barrier 11 in accordance with all the rules, namely with an overlap of at least 10 cm and glued all the joints with a vapor-tight tape, then water vapor will not penetrate into the roof structure and will not will soak the insulation. But before the laying of this lower vapor barrier 11, the insulation 9 had to dry out. If he did not have time to dry, then there is a high probability of formation of mold in the insulation 9. The same threatens the insulation 9 in the event of the slightest damage to the lower vapor barrier 11. Because the steam will have nowhere to go except accumulate under the vapor barrier 8, soak at the heater and promote the formation of fungus in it. Therefore, in a good way, you need to remove vapor barrier 8 altogether, and make a ventilation gap of 4 cm between vapor barrier 11 and 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, bitumen will simply drain to the roof overhang. In simple words- roofing felt will not last long in a pitched roof, it's hard to even say how much, but I don't think it's more than 2 - 5 years. Secondly, the waterproofing (roofing material) is 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 figure, the rafters are just higher), or by laying a counter-lattice along the rafters. Your waterproofing is laid on the crate (which, unlike the counter-crate, lies across the rafters), so all the moisture that will accumulate under the waterproofing will soak the crate and it will also not last long. Therefore, in a good way, the roof also needs to be redone from above: replace the roofing material with a waterproofing film, and at the same time lay it on the rafters (if they protrude at least 2 cm above the insulation) or on a counter-lattice laid along the rafters. Ask clarifying questions. answer |
When insulating walls wooden house many make at least one of the four most insidious mistakes that lead to rapid rotting of the walls.
It is important to understand that the inner warm space of the house is always saturated with steam. Steam is contained in the air exhaled by a person, it is formed in large quantities in bathrooms, kitchens. However, the higher the air temperature, the large quantity a couple he can hold. When the temperature drops, the ability to retain moisture in the air decreases, and the excess falls out as condensate on colder surfaces. It is not difficult to guess what the moisture supply of wooden structures will lead to. Therefore, I would like to identify 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 the cold wooden surface walls.
But if it's the only one affordable option insulation, then you must definitely take care of the presence of a vapor barrier and two ventilation gaps.
Ideally, the “pie” of the wall should look like this:
- interior decoration;
- ventilation gap ~30 mm;
- high-quality vapor barrier;
- heater;
- membrane (waterproofing);
- second ventilation gap;
- wooden wall.
At the same time, it must be remembered that the thicker the insulation layer, the smaller the difference between the external and internal temperatures will be required for condensation to form 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 approximately one meter from each other.
If the house is located in warm regions, and the temperature difference between 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.
The use of vapor barrier for insulation outside
Placing a vapor barrier on the outer part of the wall is more serious mistake, especially if the walls inside the room are not protected by this very vapor barrier.
The beam absorbs moisture from the air well, and if it is waterproofed on one side, expect trouble.
The correct version of the "pie" for external insulation looks like this:
Interior decoration (9);
- vapor barrier (8);
- wooden wall (6);
- insulation (4);
- waterproofing (3);
- ventilation gap (2);
- exterior finish (1).
The use of insulation with low vapor permeability
Using insulation with low vapor permeability when insulating walls from the outside, such as extruded polystyrene foam boards, will be equivalent to placing a vapor barrier on the wall. Such material will block moisture on the wooden wall and will promote decay.
Heaters are placed on wooden walls with an equivalent or greater vapor permeability than wood. Various mineral wool insulation and ecowools are perfect here.
Lack of ventilation gap between insulation and 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 release 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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Insulation with stone wool of a house made of timber from the inside with only vapor barrier Do vapor barrier from the outside where are the spotlights on the attic floor
Hand on heart, it is better not to insulate solid wood houses at all. High-quality massive logs and beams, being stored in in kind provide an optimal microclimate in the house. Wood, unlike most other wall materials, "breathes", this is one of its main advantages. However, in case insufficient thickness wooden walls, or if the house has already stood for many years and the logs need protection from external influences, external insulation and sheathing are reasonable measures, help to reduce heating costs and extend the life of decaying wood. Most practical material for exterior cladding of a wooden house - vinyl siding. It is inexpensive, has a service life of half a century or more, is easy to install, and can be repaired without problems. The house, sheathed with siding, looks neat. Let's talk about how it should be proper insulation wooden house for siding.
To improve thermal insulation without worsening the microclimate and without harming the building, you need to understand the specifics of the construction and operation of a wooden house. Let's start with the theory: a little bit about woodworking and a bit of building physics.
Wood moisture and harmful fungi
We all know how quickly mold fungi attack wood that is constantly wet. 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 are created for the vital activity of fungi, can turn into dust. The main condition for the growth of mold is a sufficient amount of moisture. Accordingly, in order to preserve a wooden house for many years, its walls and other structures must be protected from waterlogging. The absolute humidity (the ratio of the mass of water to the weight of absolutely dry wood) of a freshly cut coniferous forest reaches 90%, a log house before installation - 25-35%, a wooden house, under normal conditions, defended during the year - 10-20% depending on the season. At the same time, the fungal infection of wood begins to develop from a moisture level of 22%, which is only slightly higher than the natural state of the log house. By the way, these same conditions are suitable for the wood-boring beetle to settle in the logs.
It is important to know: in no case should waterlogged wood be allowed - the main reason for its destruction.
Overwatering a tree causes it to rot.
Where does moisture get into wood?
There is an opinion that moisture enters the walls of a wooden house from the outside with slanting rain, fog and snow. Precipitation really moistens the walls. But wet weather does not last that long, the sun and especially the wind contribute quick removal excess moisture. An attentive reader will say: the average annual air humidity in the street is 78% (data for the Moscow region), and in the house it fluctuates between 40-70% - which means that there is more moisture on the street and it should penetrate from outside to 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 temperature. And the colder the air, the less moisture it can hold. To understand the actual moisture content of the air, building physics uses absolute humidity values. In summer, when the temperature is about the same outside and inside the house, the humidity is similar. But in winter and in the off-season, the picture is completely different. For example, when the outside temperature is -20 ºС and the relative humidity of the outside air is 80% absolute value will be 0.6 g / m3, and inside the house at 20 ºС and relative humidity of 60% absolute 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 "breathable" interventional insulation.
It is important to know: most of the year, with the exception of the warm period, water vapor penetrates the wood from inside the house and tends to go 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 out 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 prevent the free exit of water vapor to the outside.
Modern designs in wooden (and not only) housing construction imply the widespread use of vapor barrier and windproof films. The first are absolutely tight, do not let air or steam through. The latter repel water drops, but do not prevent 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 up” with wind insulation: it counteracts the blowing of the insulation, does not allow drops of water to get inside from the outside (condensate may form on the inner surface of the siding), while water vapor freely escapes. Since the insulation is covered with a finishing material (in our case, it is siding), there must be a ventilation gap between the insulation and the finish so that excess moisture can leave the wall structure.
Important to know: ventilation gap - required element insulation structures for siding and other sheathing materials.
Many covens, internet sources, construction company managers 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, completes the design of the ventilation gap and finishing material, siding in our case. This does not take into account that the moisture tending to the outside will hit the vapor barrier, the humidity in the area adjacent to the vapor barrier will increase, and if a dew point occurs, condensate will fall. Conditions will be created for the germination of fungal spores, and from the inside we will not notice the destruction of wood that has begun for a long time.
The windproof film (diffusion membrane) has many micro-holes, due to which it passes steam, at the same time, water drops roll off the material
The eternal question: what to do?
We support the point of view of those specialists in building physics and technologists working in the field wooden housing construction that vapor barrier is not needed when insulating a wooden house. The only case where the placement of a vapor barrier between bearing wall and insulation can be justified - the house (cottage) is used seasonally, rarely heated in winter, or the minimum temperature is maintained in the rooms and they are well ventilated. With this mode of operation, the temperature difference and, accordingly, the absolute humidity outside and inside is low. For a house where people live permanently, there are internal sources moisture (breath of people, steam from kitchen pots and showers, moisture from watering house plants), vapor barrier is more likely to do harm than good. 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 cardboard, kraft paper, and even 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 a vapor barrier, supporters of its placement say that the insulation that is not protected from steam penetration will be moistened and its thermal performance will deteriorate. Alas, they are right. But the ventilation gap contributes to the removal of moisture, and a relatively small (5-15%) drop in heat-shielding properties is a forced sacrifice in the struggle for the durability of the building.
It is important to know: when insulating a wooden house in which they live all year round, vapor barrier is not needed.
This cannot be done if the house is inhabited all year round! Walls “wrapped” in glassine will become waterlogged and become defenseless against mold fungi
Material for the frame and the "correct" insulation
For the frame, use only flat wooden blocks, preferably antiseptic. Steel profiles, which recommend the use of "sofa" masters, freeze through, besides, condensate appears on them, which does not benefit either the insulation or the walls.
The cross section of the bars must correspond to the thickness of the insulation, for mineral wool this is usually 5 cm. Accordingly, the bars are 5x5 or 4x5 cm. The recommended ventilation gap is 4-5 cm, therefore, the same material can be used for the counter rail, which provides the necessary distance between the insulation and the siding.
The insulation should be vapor permeable and lightweight. The most affordable is semi-rigid mineral wool mats, soft rolls should not be used, they will eventually shrink in the wall. Ideal for a wooden house, eco-friendly, very durable, but alas, expensive material - linen and hemp mats. Cellulose wool, wool waste can be filled between the wall and the wind protection. Again, the main thing for a heater is vapor permeability. Mineral wool can be placed in two layers (10 cm) or one (5 cm). What should be the total layer of insulation, decide based on climatic conditions and thickness existing walls.
Linen mats have much longer fibers than mineral wool, so they hold their shape better and longer.
Work production technology
The technology of warming 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 is equal to the width of the insulation, for mineral wool it is 50 cm.
- We recommend mounting the first level of bars vertically. The second, if the insulation is laid in two layers, is horizontal. The counter rail to which the siding will be directly attached is vertical.
Frame for warming the log house with mineral wool in two layers.
- On the uneven walls it is convenient to fasten the bars with the help of perforated plasterboard hangers. Time-consuming, but preferable from the point of view of heat engineering will be traditional method: adjust the distance from the wall by placing wooden lugs. Screws will fix the frame better than nails.
Options for the device 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 material settling.
- After sewing on the frame and filling the gaps between its elements with a heater, they fix the wind protection, on top of it - the counter rail.
The frame is filled with insulation, the next step is wind protection
- The final work is the sheathing of a wooden house with siding.
The "correct" design of wall insulation for siding with double layer mineral wool.
In the ventilated gap, free air flow must be ensured. For this in outer skin gaps are left at the top and bottom of the walls (closed with a mesh from mice and insects) or gratings are inserted into the siding panels.
Important to know: ventilation holes should be located at the bottom and top of the wall sheathing.
Not everyone has the opportunity and the necessary skills to perform such work. If there is no self-confidence, it is better to entrust the insulation of your own house and lining it with siding experienced craftsmen.
Video: wooden house - how to sheathe and how to insulate
Bridges of cold call the sections of the building envelope through which the greatest 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 (mansard) structure.
Cold bridges in insulated construction pitched roof causes many problems:
- Firstly, they reduce the effectiveness of the thermal protection of the building, which increases energy consumption by , which, in turn, results in an increase in the cost of operating the house.
- Secondly, during the cold season, condensate accumulates in the freezing zone, which leads to wetting and gradual damage to the roof used for insulation (which also worsens the thermal protection of the building).
- Thirdly, due to condensate, wooden roof structures can become moldy, rot and eventually collapse. Often, condensation causes deformation of the finish.
- Finally, fourthly, condensate can freeze in winter and break the cracks and gaps that it filled.
Heating errors
What causes cold bridges? According to experts, in most cases this is due to errors in the construction of the heat-insulating layer of the roofing "pie". Recall that the most common technology for the construction of a mansard roof involves the insulation of slopes (which are at the same time the walls of the attic) with fibrous materials: slabs and - less often - mats based on or.
Another knot dangerous in terms of freezing is the junction of the roof with the gable of the building.
Valery Nesterov, general manager Dörken company:
“At the junction of the roof with the pediment of the building, the probability of freezing is very high. 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 30 mm thick made of non-woven material: they can also protect this area from freezing. However, the traditional solution is to fill mineral thermal insulation the space between the extreme rafter and the gable wall (usually about 50 mm), the gap between the upper surface of the wall and the hydro-windproof film, and also lay the insulation along the upper edge of the wall. As a result, a continuous heat-insulating contour is created that closes the pediment and transfers the dew point inside the wall, thereby eliminating the possibility of condensation in the thickness of the roofing insulation.”
- The first difficulty lies in the fact that often on the entire upper part of the inclined gable wall there are ledges formed due to masonry (made of bricks, blocks). To level the wall, often use "cold" cement-sand mortar, which becomes a bridge of cold. It is better to use a "warm" solution with the addition of it instead. Or fill the irregularities with thermal insulation.
- 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 leg 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 leg, ensuring its snug fit to the insulation running along the rafters. If possible, the insulation is also mounted along its edge from the side of the street - with a layer of thickness equal to the thickness of the insulation on the roof slope.
Freezing through the rafters
Joints are also problematic. wooden elements roofs (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 the settlement of the truss system, etc. To avoid this, joints should be laid with sealing materials, for example, synthetic winterizer or polyethylene foam. 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 the installation of the rafters, then you can use specialized sealants, PSUL (pre-compressed self-expanding sealing tapes) or mounting foam However, this is not cheap and rather laborious. This solution has one more significant disadvantage: the foam, being inelastic, can collapse when the wooden structure is upset.An effective way to prevent heat loss- create an additional layer of roof insulation, blocking possible cold bridges.
On the picture:
1. On roofs of complex configuration, it is inevitable to cut the insulation boards in order to fit them into the space between the rafters.
2. Mount vapor barrier film to the rafter leg.
3. Installing the undercut slab in the ridge area.
4. Slots in the insulation layer are caulked with fragments of the same heat-insulating material.
Freezing is also possible in places where the Mauerlat, ridge or intermediate runs through the wall go out onto the street, on which the extended rafters rely. To prevent the movement of cold air here, you must first 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 roof window area is another section of the roof where cold bridges can occur.
Often this happens due to the absence or insufficient thickness of the insulation layer around the perimeter. window frame and along slopes. In order 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 to the roof insulation contour.
To simplify installation, window manufacturers offer ready-made kits for thermal insulation around the perimeter of the frame(e.g. polyethylene foam). Some companies produce windows with heat-insulating ones already provided on the frame. Note that window manufacturers categorically prohibit insulating the frame with mounting foam.
Marina Prozarovskaya, Chief Engineer Velux company:
“Among the reasons for freezing in the area of the roof window is the lack of thermal insulation around the perimeter of the window frame. Often this is caused by too small mounting gaps between the box and the rafters. It is necessary to leave a gap of at least 30 mm around the perimeter of the frame, installing either a ready-made heat-insulating contour made of polyethylene foam or a fibrous insulation around it. Mounting foam cannot be used for these purposes: it is inelastic and under the influence of periodic loads (roof settlement, snow, wind load) crumbles, resulting in cracks in the thermal insulation. If the width of the window is equal to the width of the inter-rafter opening or exceeds it, then in order to provide the necessary mounting gaps around the frame, it will be necessary to adjust the rafters, while maintaining their bearing capacity. Sometimes this can be done without special calculation according to the schemes indicated in the window installation instructions. Usually this 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, non-glued joints of the vapor barrier film with the window frame: water vapor has a high penetrating ability, and when it enters the cold zone, it condenses. Often, condensation is a consequence of certain errors in the installation of the ventilation system of the roof structure.
For example, there are no conditions for air inflow or its exhaust, a counter-lattice that forms a ventilation gap is not provided, or its height is insufficient to provide the necessary air movement under. However, non-sealed joints and junctions of both roofing films, as well as insufficient ventilation of the roofing space are errors that lead to condensation and freezing. not only in the window area, but throughout the roof. It's just in the window area that it becomes noticeable in the first place. Moreover, many errors cannot be corrected during the operation of the building without the complete dismantling of the roof.
According to experts, in the conditions of the Moscow region every 5 cm of thermal insulation saves on heating an average of 18 rubles. per 1 sq. m of roof area per year.
A few more words about the roof window. Problems arise and in case of improper installation of the drainage gutter above window opening. This gutter removes water (leaks, condensate) 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 window waterproofing apron is already inserted under the gutter. If the gutter installation technology is not followed, leakage into the insulation is possible with all the ensuing consequences.
Heat-conducting inclusions in the roof structure become certain passage elements - pipes, antennas, flagpoles, etc. Therefore, they must be insulated with high quality and vapor barrier and hydro-windproof films should be hermetically joined to them.
To minimize freezing through the walls, experts advise creating an additional heat-insulating belt about 250 mm high on top of the standard insulation contour (that is, above the roof). To protect against precipitation, the belt must be closed with one or another apron.
Ekaterina Kolotushkina, Product Manager, 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 circuit. The fact is that the wooden load-bearing elements of the roof 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 rafters is 150 mm (and the insulation is placed in the space between the rafters). Thus, it makes sense to create an additional thermal insulation layer, which will provide the required thickness of insulation and block the cold bridges going through the rafters. This layer can be placed above and below the rafters, laying the insulation between the bars nailed across the rafters. Thermal insulation above the rafters is preferable, because in this case they do not freeze through.
Additional layer of insulation
Despite all the efforts of roofers, heat losses are inevitable in those places on the roof where the area of the inner “warm” surface is less than the area of \u200b\u200bthe outer “cold” one. These are mainly the angles of the hip or hipped roofs(in the zone of convergence of the ridge and eaves overhang), places where the slope adjoins the pediment, etc. In addition, wooden rafter legs are also, to a certain extent, cold bridges. Yes, and it is difficult to insulate complex sections of the roof where filigree pruning is required (valleys, ridges, junctions). Finally, the thickness of the heat-insulating layer in central Russia should be, according to SNiP 23-02-2003 "Thermal protection of buildings", not less than 200 mm. While the most popular material for the construction of rafters is still a section of 150 × 50 mm, which implies a thickness of the inter-rafter insulation layer of 150 mm. All these factors justify the need for additional contour of the thermal insulation of the roof.It can be mounted over the rafters and under them. In the first case:
- Wooden blocks of the required section are stuffed across the rafters, between which insulation plates are installed.
- A hydro-windproof membrane is laid over the bars.
- A counter-lattice, crate or solid flooring is fixed on it, and roofing material is placed on them.
- Fixing the roof to the base is less reliable due to the additional wooden substructure.
- In addition, when installing hydrowind protection, the joints of the sheets may be on the insulation (and not on wooden base), and the installers will push through the film, moving along the roof.
There is another effective, but so far almost unused method of insulation - installation over rafters continuous 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 contour of warming.
3. Cross bar.
4. Finishing the attic.
Let's note one more point. In the fight against freezing of the roof will help modern methods detection of cold bridges- 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 freezing 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 thermographic examination of buildings.
Types of insulation for pitched roofs
To insulate a pitched roof, slabs (or mats) made of stone or glass fiber are most often used.- In our market, stone fiber materials are represented by Rockwool (Denmark), Paroc (Finland), Nobasil (Slovakia), TechnoNikol, Isoroc, Knauf (all Russia) and others.
- Glass fiber insulation is offered by Isover (France), Ursa (Spain) and others.
Materials made of extruded polystyrene foam or polyurethane foam, 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, fibrous heaters are non-combustible (NG).
The material was prepared by Alexander Levenko.
If you live in the Leningrad region, then you know that our climate is not the most gentle. There are few sunny days, the average annual temperature is from 2 to 4.5 degrees Celsius.
Therefore, it is possible to spend time comfortably in the country only in three summer months (depending on what kind of summer).
But this period can be lengthened if the house is insulated 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 be clear right away: professionals don't make these mistakes. Each siding installation 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 - drive them to 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.
Roll insulation instead of slab
This mistake is caused by the desire to save on materials when insulating the house.
Roll insulation is cheaper than slab insulation, and those who do not understand insulation technology are tempted to save money.
Insulate vertical surfaces roll insulation it is forbidden. It is intended for horizontal surfaces and flat roofs(with an angle of inclination of 6:1 and more flat).
If you insulate the walls with rolled insulation, then it will very quickly fall to the bottom of the wall, and the top of the wall will give off all the heat of your house to the street.
Therefore, when insulating a house under siding, slab insulation should always be used (we usually use mineral wool).
Loose joints between insulation boards
If the plates do not fit tightly to each other, then, in fact, a gap forms in the warm wall of your house.
Heat is like water, it flows 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 a great one.
Your house will become warmer than before insulation, but some of the heat will still go away. And I don't think you need it at all.
Therefore, make sure that the people who insulate the walls of your house join the insulation boards tightly without gaps.
When they cover it all with windproofing, you will no longer see anything, and your house will not be effectively insulated under the siding.
Loose insulation boards
Some home-grown "craftsmen" will confidently tell you that the slab insulation is quite dense, and you don't need to attach 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 heater weighs a little, but it load bearing capacity- very low. Therefore, the plate, which is pressed by a column of mineral wool three meters high, one way or another, will settle.
Professionals fasten each insulation plate with special "parachutes". This relieves the bottom plate because each top plate hangs on its own fastener.
Wall insulation under siding without ventilation gap
Siding installation technology provides for the creation of a ventilated gap between the siding and the wall of the house.
This space serves to drain condensate into the soffit under the roof.
In the ventilation gap, the upward 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 the formation of fungus and mold.
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 provides condensate removal to the roof overhang and reliable ventilation siding insulation.
Cold bridges when insulating walls under siding
Most coven workers, "wild brigades" and even some firms mount the siding frame on "kolobashki".
A bell is a piece of wood between the wall and the frame, to which the siding is then attached. It aligns the frame in a vertical plane so that the wall becomes even after sheathing with siding.
The bell is screwed to the wall, and a 50x50 mm bar is screwed to it, between which a heater is laid.
This is the most common way for non-professionals to insulate walls under siding.
But the question arises: what prevents the heat from leaving your house in those places where the frame passes?
Nothing interferes.
Heat escapes 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 gaps under the frame are much wider (along the width of the bar).
This problem is solved fundamentally different approach to the insulation of the house under the 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.
