Is a gap necessary? Why do you need a ventilation gap in a frame house, a ventilation gap on the facades. Materials with vapor barrier properties
A house made of porous blocks cannot be left without moisture-resistant finishing - it must be plastered, lined with bricks (unless provided additional insulation, then without a gap) or mount curtain façade. Photo: Wienerberger
In multi-layer walls with insulation mineral wool a ventilation layer is necessary, since the dew point is usually located at the junction of the insulation with the masonry or in the thickness of the insulation, and its insulating properties sharply deteriorate when moistened. Photo: YUKAR
Today the market offers a huge variety construction technologies, and this often results in confusion. For example, the thesis has become widespread, according to which the vapor permeability of layers in the wall should increase towards the street: only in this way will it be possible to avoid over-wetting the wall with water vapor from the premises. Sometimes it is interpreted as follows: if the outer layer of the wall is made of a denser material, then there must be a ventilated air layer between it and the masonry of porous blocks.
Often a gap is left in any walls with brick cladding. However, for example, masonry made of lightweight polystyrene concrete blocks practically does not allow steam to pass through, which means there is no need for a ventilation layer. Photo: DOK-52
When used for finishing clinker, a ventilation gap is usually necessary, since this material has low coefficient steam transmission. Photo: Klienkerhause
Meanwhile, building codes mention a ventilated layer only in connection with, but in the general case, protection from waterlogging of walls “should be ensured by designing enclosing structures with a vapor permeability resistance of internal layers of at least the required value determined by calculation...” (SP 50.13330.2012, P. 8.1). The normal humidity regime of three-layer walls of high-rise buildings is achieved due to the fact that the inner layer of reinforced concrete has a high resistance to vapor transmission.
Common mistake builders: there is a gap, but it is not ventilated. Photo: MSK
The problem is that some multilayer masonry structures used in low-rise housing construction physical properties closer to . Classic example- a wall made of (one block) lined with clinker. Its inner layer has a vapor permeability resistance (R p) equal to approximately 2.7 m 2 h Pa/mg, and the outer layer is about 3.5 m 2 h Pa/mg (R p = δ/μ, where δ - layer thickness, μ - coefficient of vapor permeability of the material). Accordingly, there is a possibility that the increase in humidity in foam concrete will exceed the tolerances (6% by weight during the heating period). This can affect the microclimate in the building and the service life of the walls, so the wall similar design It makes sense to lay it with a ventilated layer.
In such a design (with insulation with sheets of extruded polystyrene foam) there is simply no room for a ventilation gap. However, EPS will interfere gas silicate blocks dry, so many builders recommend vapor barriering such a wall from the side of the room. Photo: SK-159
In the case of a wall made of Porotherm blocks (and analogues) and conventional slotted facing bricks The vapor permeability indicators of the inner and outer layers of masonry will differ insignificantly, so the ventilation gap will be more likely to be harmful, as it will reduce the strength of the wall and require an increase in the width of the base part of the foundation.
Important:
- A gap in the masonry becomes meaningless if entrances and exits from it are not provided. At the bottom of the wall, immediately above the plinth, it is required to be built into the facing masonry ventilation grates, the total area of which must be at least 1/5 of the horizontal sectional area of the gap. Usually, 10x20 cm gratings are installed in increments of 2–3 m (alas, the gratings are not always available and require periodic replacement). In the upper part, the gap is not laid or filled with a solution, but is closed with a polymer masonry mesh, even better - perforated panels made of galvanized steel with a polymer coating.
- The ventilation gap must be at least 30 mm wide. It should not be confused with the technological one (about 10 mm), which is left for leveling brick cladding and during the laying process, as a rule, they are filled with mortar.
- There is no need for a ventilated layer if the walls are tightened from the inside vapor barrier film followed by finishing
Ventilation gap in frame house- this is a moment that often raises many questions among people who are involved in insulating their own home. These questions arise for a reason, since the need for a ventilation gap is a factor that has a huge number of nuances, which we will talk about in today’s article.
The gap itself is the space that is located between the sheathing and the wall of the house. Implemented similar solution by means of bars that are attached on top of the windproof membrane and on the external finishing elements. For example, the same siding is always attached to bars that make the facade ventilated. A special film is often used as insulation, with the help of which the house, in fact, is completely wrapped.
Many will rightly ask, is it really not possible to just take and attach the sheathing directly to the wall? Do they just line up and form an ideal area for installing sheathing? In fact, there are a number of rules that determine the necessity or unnecessaryness of organizing a ventilation facade. Let's figure out whether a ventilation gap is needed in a frame house?
When is a ventilation gap (vent gap) needed in a frame house?
So, if you are thinking about whether a ventilation gap is needed in the facade of your carcass house, pay attention to the following list:
- When wet If the insulation material loses its properties when wet, then a gap is necessary, otherwise all work, for example, on insulating a home, will be completely in vain
- Steam Permeation The material from which the walls of your home are made allows steam to pass through into the outer layer. Here, without organizing free space between the surface of the walls and insulation, it is simply necessary.
- Preventing excess moisture One of the most common questions is the following: is there a need for a ventilation gap between vapor barriers? If the finish is a vapor barrier or moisture-condensing material, it must be constantly ventilated so that excess water is not retained in its structure.
As for the last point, the list of similar models includes following types sheathing: vinyl and metal siding, profiled sheets. If they are sewn tightly on flat wall, then the remaining accumulated water will have nowhere to go. As a result, materials quickly lose their properties and also begin to deteriorate externally.
Is there a need for a ventilation gap between siding and OSB?
When answering the question of whether a ventilation gap is needed between the siding and OSB (from English - OSB), it is also necessary to mention its need. As already stated, siding is a product that insulates vapor and OSB board consists entirely of wood shavings, which easily accumulates residual moisture and can quickly deteriorate under its influence.
Additional reasons to use a ventilation gap
Let's look at a few more mandatory points when clearance is a necessary aspect:
- Preventing rot and cracks The wall material under the decorative layer is prone to deformation and deterioration when exposed to moisture. To prevent rot and cracks from forming, just ventilate the surface, and everything will be fine.
- Preventing condensation The material of the decorative layer may contribute to the formation of condensation. This excess water must be removed immediately.
For example, if the walls of your house are made of wood, then an increased level of moisture will negatively affect the condition of the material. Wood swells, begins to rot, and microorganisms and bacteria can easily settle inside it. Of course, a small amount of moisture will collect inside, but not on the wall, but on a special metal layer, from which the liquid begins to evaporate and be carried away with the wind.
Is there a need for a ventilation gap in the floor? No
Here you need to take into account several factors that determine whether you need to make a gap in the floor:
- If both floors of your house are heated, then a gap is not necessary If only the 1st floor is heated, then it is enough to lay a vapor barrier on its side to prevent condensation from forming in the ceilings.
- The ventilation gap must be attached only to the finished floor!
When answering the question of whether a ventilation gap is needed in the ceiling, it should be noted that in other cases this idea is purely optional and also depends on the material chosen for insulating the floor. If it absorbs moisture, then ventilation is simply necessary.
When a ventilation gap is not needed
Below are a few cases where this construction aspect does not need to be implemented:
- If the walls of the house are made of concrete If the walls of your house are made, for example, of concrete, then you don’t need to make a ventilation gap, since this material does not allow steam to pass from the room to the outside. Consequently, there will be nothing to ventilate.
- If there is a vapor barrier inside the room If a vapor barrier was installed on the inside of the room, then the gap also does not need to be organized. Excess moisture simply will not come out through the wall, so there is no need to dry it.
- If the walls are treated with plaster If your walls are treated e.g. facade plaster, then the gap is not needed. In case outer material the treatment allows steam to pass through well; no additional measures are required to ventilate the casing.
Installation example without ventilation gap
As a small example, let's look at an installation example without the need for a ventilation gap:
- At the beginning there is a wall
- Insulation
- Special reinforcing mesh
- Mushroom dowel used for fastening
- Facade plaster
Thus, any amounts of steam that penetrate the structure of the insulation will be immediately removed through the layer of plaster, as well as through vapor-permeable paint. As you may have noticed, there are no gaps between the insulation and the decoration layer.
We answer the question why a ventilation gap is needed
The gap is necessary for air convection, which can dry out excess moisture and have a positive effect on the safety building materials. The very idea of this procedure is based on the laws of physics. Ever since school we have known that warm air always goes up and cold always goes down. Consequently, it is always in a circulating state, which prevents liquid from settling on surfaces. In the upper part, for example, of the siding, perforations are always made, through which steam escapes out and does not stagnate. Everything is very simple!
| 7 years ago | tanya (Builderclub expert) First, I’ll 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 placed under the insulation in order to retain water vapor from inside the room, and thereby protect the insulation from getting wet. For complete tightness, the joints of the vapor barrier are taped with vapor barrier tape. As a result, vapors accumulate under the vapor barrier. To ensure that they erode and do not soak the internal lining (for example, gypsum board), a gap of 4 cm is left between the vapor barrier and the internal lining. The gap is ensured by laying the sheathing. The insulation on top is protected from getting wet. waterproofing material. If the vapor barrier under the insulation is laid according to all the rules and is perfectly 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 operation of the roof, a ventilation gap is created between the waterproofing and the insulation. Because even the slightest, invisible damage to the vapor barrier allows water vapor to penetrate into the insulation. Passing through the insulation, vapors accumulate on inner surface waterproofing film. Therefore, if the insulation is laid close to waterproofing film, then 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 must be a ventilation gap of 2-4 cm between the waterproofing and the insulation. Now let's look at the structure of your roof. Before you laid insulation 9, as well as vapor barrier 11 and gypsum board 12, water vapor accumulated under vapor barrier 8, there was free access of air from below and they evaporated, 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) became noticeable to you. A few days later, you laid vapor barrier 11 under this insulation and sewed up gypsum board 12. If you laid the lower vapor barrier 11 according to all the rules, namely with an overlap of at least 10 cm and taped all joints with vapor-proof tape, then water vapor will not penetrate into the roof structure and will not the insulation will be soaked. But before this lower vapor barrier 11 was laid, insulation 9 had to dry out. If it has not had time to dry, then there is a high probability of mold forming in the insulation 9. This also 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 to accumulate under the vapor barrier 8, soaking the insulation and promoting the formation of fungus in it. Therefore, in an amicable way, you need to completely remove the vapor barrier 8, and make a ventilation gap of 4 cm between the vapor barrier 11 and the gypsum board 12, otherwise the gypsum board will get wet and bloom over time. Now a few words about waterproofing. First, roofing felt is not intended for waterproofing pitched roofs; it is a bitumen-containing material and in extreme heat the bitumen will simply flow down to the roof overhang. In simple words- roofing felt will not last long pitched roof, it’s hard to even say how long, but I don’t think it’s more than 2 - 5 years. Second, the waterproofing (roofing felt) was not installed 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 by the fact that the rafters are higher than the layer of insulation laid between them (the rafters in your picture are just higher), or by laying counter-lattice along the rafters. Your waterproofing is laid on the sheathing (which, unlike the counter-lattice, lies across the rafters), so all the moisture that accumulates under the waterproofing will soak the sheathing and it will also not last long. Therefore, in an amicable way, the top of the roof also needs to be redone: replace roofing felt with waterproofing film, and 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 |
To reduce the costs associated with heating your home, it is definitely worth investing in wall insulation. Before delving into the search for a team of façade designers, it is advisable to prepare properly. Here is a list of the most common mistakes that can be made when insulating a house.
Absence or poorly executed wall insulation project
The main task of the project is to determine the optimal thermal insulation material (mineral wool or polystyrene foam) and its thickness in accordance with building codes. Also, a pre-prepared house insulation project gives the customer the opportunity to clearly control the work performed by contractors, for example, the layout of insulation sheets and the number of fasteners on square meter, and workarounds window openings, as well as much more.
Carrying out work at temperatures below 5° or above 25°, or during precipitation
The consequence of this is that the glue between the insulation and the base dries too quickly, as a result of which the adhesion between the layers of the wall insulation system is not reliable.
Ignoring site preparation
The contractor must protect all windows from dirt by covering them with film. In addition, (especially when insulating large buildings) it is good if the scaffolding is covered with a mesh, which will protect the insulated facade from excessive sunlight and the wind, allowing finishing materials dry more evenly.
Insufficient surface preparation
The surface of the insulated wall must have sufficient bearing capacity and be smooth, level and free of dust to ensure good adhesion for the adhesive. Uneven plaster and any other defects must be corrected. It is unacceptable to leave mold, efflorescence, etc. residues on insulated walls. Of course, it is necessary to first eliminate the cause of their occurrence and remove them from the wall.
No starting bar
By installing the base profile, the level of the bottom layer of insulation is set. This bar also takes on part of the load from the weight. thermal insulation material. And, in addition, such a strip helps protect the lower end of the insulation from the penetration of rodents
There should be a gap of about 2-3 mm between the slats.
Installation of slabs is not staggered.
A common problem is the appearance of gaps between slabs.
The insulation slabs must be installed carefully and tightly in a checkerboard pattern, that is, offset by half the length of the slab from bottom to top, starting from the corner wall.
Incorrect application of glue
It is incorrect when gluing is carried out only by applying “bloopers” and does not apply a layer of glue around the perimeter of the sheet. The consequence of such gluing may be the bending of the insulation boards or the marking of their outline on the final finishing of the insulated facade.
Options correct application glue for foam:
- along the perimeter in the form of stripes with a width of 4-6 cm. On the remaining surface of the insulation - dotted “bloopers” (from 3 to 8 pieces). The total area of the adhesive should cover at least 40% of the foam sheet;
- applying glue to the entire surface with a ridge spatula - used only if the walls are pre-plastered.
Note: adhesive solution Apply only to the surface of the thermal insulation, never to the base.
Gluing mineral wool requires preliminary puttying of the slab surface. Thin layer cement mortar rub into the surface of the mineral wool.
Insufficient fastening of thermal insulation to the load-bearing surface
This may be the result of careless application of adhesive, the use of materials with inappropriate parameters, or too weak mechanical fastening. Mechanical connections are all kinds of dowels and anchors. Don't skimp on mechanical fastening insulation, be it heavy mineral wool or light foam.
The place of fastening with a dowel must coincide with the place where the glue (blooper) is applied on the inside of the insulation
The dowels must be properly embedded in the insulation. Pressing too deeply leads to damage to the insulation boards and the formation of a cold bridge. Too small and it will cause a bulge that will be visible on the façade.
Leaving thermal insulation unprotected from weather conditions.
Exposed mineral wool easily absorbs water, and polystyrene foam in the sun is subject to surface erosion, which can impair the adhesion of wall insulation layers. Thermal insulation materials must be protected from atmospheric influences, both when they are stored on a construction site and when they are used to insulate walls. Walls insulated with mineral wool must be protected by a roof to prevent them from getting wet by rain - because if this happens they will dry very slowly and wet insulation is not effective. Walls insulated with foam plastic cannot be exposed to prolonged exposure to direct sunlight. By long-term we mean more than 2-3 months.
Incorrect laying of insulation boards in the corners of openings
To insulate walls in the corners of window or door openings, the insulation must be cut appropriately so that the intersection of the slabs does not occur at the corners of the openings. This, of course, significantly increases the amount of waste thermal insulation material, but can significantly reduce the risk of cracks in the plaster in these places.
Not sanding the glued foam layer
This operation takes a long time and is quite labor intensive. For this reason, it is not popular among contractors. As a result, curvature may form on the facade.
Mistakes when laying fiberglass mesh
The reinforcing layer of wall insulation provides protection from mechanical damage. It is made from fiberglass mesh and reduces thermal deformation, increases strength and prevents the formation of cracks.
The mesh must be completely immersed in the adhesive layer. It is important that the mesh is glued without folds.
In places vulnerable to loads, an additional layer of reinforcement is performed - in all corners of window and doorways, mesh strips measuring at least 35x25 are glued at an angle of 45°. This prevents cracks from forming in the corners of openings.
To strengthen the corners of the house - used corner profiles with mesh.
Not filling the seams between the insulation
The result is the formation of cold bridges. To fill gaps up to 4 mm wide, use polyurethane foam for the facade.
Not using primer before coat decorative plaster
Some people mistakenly apply finishing decorative plaster directly to the mesh layer, abandoning the special (not cheap) primer. This leads to improper gluing of decorative plaster and the appearance of gaps gray from glue and the rough surface of the insulated facade. In addition, after a few years, such plaster cracks and falls off in pieces.
Mistakes when applying decorative plaster
Thin-film plasters can be performed after 3 days from the date of completion of the reinforcing layer.
The work must be organized so that the team works without interruptions on at least 2 or 3 levels of scaffolding. This prevents the appearance of uneven color on the facade due to its drying at different times.
In this article I will consider the issues of ventilation of the inter-wall space and the connection between this ventilation and insulation. In particular, I would like to understand why a ventilation gap is needed, how it differs from an air gap, what its functions are, and whether a gap in the wall can perform a thermal insulation function. This question becomes quite relevant in Lately and raises many 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 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 like this, in a simplified version. Particularly meticulous citizens, please write comments. We will complicate the description as we work.
The essence of the problem (subject part)
Let's understand the subject matter and agree on terms, otherwise it may turn out that we are talking about one thing, but mean completely opposite things.
This is our main subject. The wall can be uniform, 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 finishing.
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 we can give this additional element walls as a leveling frame.
Let's assume we have a newly built wooden house. We want to finish him off. First of all, we 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 the rule to the wall, it becomes clear that the wall is horribly crooked. Well... there's nothing you can do about it! WITH wooden houses that happens. We level 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, it will not be possible to make a decent exterior decoration of our house - the corners will “disintegrate.” 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 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 aimed at removing moisture from the wall and keeping it dry. Could this layer combine the technological properties of an air gap? Yes, maybe that’s what this article is being written about, in essence.
Physics of processes inside the wall Condensation
Why dry the wall? Is she getting wet or something? Yes, it gets wet. And you don't need to hose it down to get it wet. The temperature difference from the heat of the day to the coolness of the night is quite enough. The problem of getting the wall, all its layers, wet as a result of moisture condensation might 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, warm air tends to leave the warm room and again moisture condensation occurs in the thickness of the wall. Thus, the relevance of drying the wall remains at any time of the year.
Convection
Please note that the site has a good article about the theory of condensation in walls
Warm air tends to rise and cold air tends to sink. And this is very unfortunate, since in our apartments and houses we live not on the ceiling, where warm air collects, but on the floor, where cold air collects. But I seem to have gotten distracted.
It is impossible to completely get rid of convection. And this is also very unfortunate.
But let's look at a very useful question. How does convection in a wide gap differ from the same convection in a narrow gap? We have already understood that the air in the gap moves in two directions. On a warm surface it moves up, and on a cold surface it goes down. 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 quite complicated. I believe that the layer of air directly at the surface moves as quickly as possible. It pulls along layers of air that are nearby. As far as I understand, this happens due to friction. But the friction in the air is quite 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 lower the flow speed, the weaker the turbulence. If the gap is wide enough, these swirls may be completely absent or completely invisible.
But what if our gap is 20 or 30 mm? Then the turbulence can be stronger. These vortices will not only mix the flows, but also slow down each other. It seems that if you make an air gap, 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 funny examples. First example
Let us have a wall with an air gap. The gap is blank. The air in this gap has no connection with the air outside the gap. On one side of the wall it is warm, on the other it is cold. Ultimately this means that internal sides in our gap they differ in temperature in the same way. What happens in the gap? The air in the gap rises along the warm surface. When it's cold it goes down. Since this is the same air, a cycle is formed. During this cycle, heat is actively transferred from one surface to another. And actively. This means that it is strong. Question. Does our air gap perform a useful function? Looks like no. It looks like it is actively cooling 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 and forever and ever.
Second example. 
Suppose we made holes at the top and bottom so that the air in the gap communicates with outside world. What has changed for us? And the fact is that now there seems to be no cycle. Either it is there, but there is also air leaking and venting. Now the air is heated from the warm surface and, perhaps partially, flies out (warm), and cold air from the street takes 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 outside.
I will note the following. Yes, now we are heating the atmosphere, but in the first example we were heating the casing. How much is the first option worse or better than the second? You know, I think these are approximately the same options in terms of their harmfulness. My intuition tells me this, so, just in case, I don’t insist that I’m right. But in this second example we got one useful feature. Now our gap has become an air ventilation gap, that is, we have added a remote function humid air, and that means 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 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 this classification is not too strict, but the article is mine, and in it I have the right to such outrages. So here it is. A dry wall has a much lower thermal conductivity than a damp wall. As a result, heat will flow more slowly from inside warm room to the harmful air gap and being carried outside will also become less. Simply, convection will slow down, since the left surface of our gap will no longer be so warm. Physics of increasing thermal conductivity 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 does the wall ventilation process work?
Well, it's simple. Moisture appears on the surface of the wall. The air moves along the wall and carries away moisture from it. The faster the air moves, the faster the wall dries out if it is wet. It's simple. But it gets more interesting.
What wall ventilation rate do we need? This is one of the key questions of the article. By answering it, we will understand a lot about 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 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 the steam would be removed, but a lot of heat would not be taken away from the wall. Unfortunately, I cannot say how many cubes per hour should pass along our wall. But I can imagine that it’s not a lot at all. A certain compromise is needed between the benefits of ventilation and the harm from heat removal.
Interim conclusions
The time has come to sum up some results, without which we 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 it should be avoided. But I have always been kind to the phenomenon of an air gap. Why? As always, for a number of reasons. And, by the way, I can justify each one.
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, damage from the air gap does not rank first in the ranking of damage to thermal conductivity and construction mistakes.
But please remember the following to avoid future misunderstandings. An air gap can never, under any circumstances, serve to reduce the thermal conductivity of a wall. That is, the air gap cannot make the wall warmer.
And if you are going to 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 true and it's a shame. But this single function is extremely, simply vitally important. Moreover, it is simply impossible to live without it. In addition, we will next consider options for reducing harm from air and ventilation gaps while maintaining the positive functions of the latter.
A ventilation gap, as opposed to an air gap, can improve the thermal conductivity of the 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 thermal insulation layer becomes drier.
How to reduce damage 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, 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, our wall is high. It can be 3 or 7 meters or more in height. The greater the distance the air has to travel, the more porous material we should have. Most likely, foam concrete and gas silicate are not suitable.
Moreover, the tree is not suitable, ceramic brick and so on.
Styrofoam? Not! Polystyrene foam is also not suitable. It is not too easily permeable to water vapor, especially if it needs to travel more than three meters.
Bulk materials? Like expanded clay? Here, by the way, is an interesting proposal. It could probably work, but expanded clay is too inconvenient to use. It gets dusty, wakes up and all that.
Low density wool? Yes. I think very low density cotton wool is the leader for our purposes. But the 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 these arguments are good and useful only in theoretical terms. IN real life you can do it much simpler and more prosaically, which I will write about in a pathetic manner in the next section.
The main result, or what, after all, should be done in practice?
- During construction personal home There is no need to create special air and ventilation gaps. You won't achieve much benefit, but you can cause harm. If the construction technology allows you to do without a gap, don’t do it.
- If you can’t do without a gap, then you need to leave it. But you shouldn’t make it wider than circumstances and common sense require.
- If you have an air gap, is it worth expanding (converting) it to a ventilation gap? My advice: “Don’t worry about it and act according to the circumstances. If it seems like it would be better to do it, or you just want it, or this is a principled position, then make a ventilation one, but if not, leave the air one.”
- Never, under any circumstances, use materials that are less porous than the materials of the wall itself when constructing exterior decoration. This applies to roofing felt, penoplex and in some cases to polystyrene foam (expanded polystyrene) and also to polyurethane foam. Please note that if a thorough vapor barrier is installed on the inner surface of the walls, then failure to comply with this point will not cause harm other than 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 above. Or just on top. This is necessary so that convection, although weak, exists.
- But what to do 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 to either provide air access into the space between the walls (bottom and top), or provide a vapor barrier inside the room. I like the last option much better.
- If a vapor barrier was provided when installing 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. The ventilation gaps do not provide any additional thermal insulation. They just dry the wall and that's it.
- Wind protection. I believe that wind protection is not needed. The role of windbreak is performed remarkably well by itself. external finishing. Lining, siding, tiles and so on. Moreover, again, my personal opinion, the cracks in the lining do not contribute enough to the blowing out of heat to use wind protection. But this opinion is my own, it is quite controversial and I do not instruct on it. Again, wind protection manufacturers also “want to eat.” Of course, I have a substantiation for this opinion and I can give it for those 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!!!
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If there is no clarity, then read the answer to the question of a person for whom everything was also not clear and he asked me to return to the topic.
I hope that the above article answered many questions and brought clarity.
Dmitry Belkin
Article created 01/11/2013
Article edited 04/26/2013
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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 warm interior space of the house is always saturated with vapors. Steam is contained in the air exhaled by a person and is formed in large quantities in bathrooms and kitchens. Moreover, the higher the air temperature, the large quantity it can hold steam. As the temperature drops, the ability to hold moisture in the air decreases, and the excess falls out as condensation on colder surfaces. What will moisture replenishment lead to? wooden structures– it’s not difficult to guess. Therefore, I would like to identify four main mistakes that can lead to a sad result.
Insulating walls from the inside is highly undesirable, since the dew point will move inside the room, which will lead to moisture condensation in the cold wooden surface walls.
But if this is the only one affordable option insulation, then you must take care of the presence of a vapor barrier and two ventilation gaps.
Ideally, the wall “pie” should look like this:
- interior decoration;
- ventilation gap ~30 mm;
- high-quality vapor barrier;
- insulation;
- membrane (waterproofing);
- second ventilation gap;
- wooden wall.
It must be remembered that the thicker the insulation layer, the smaller the difference in external and internal temperatures will be required for the formation of condensation on wooden wall. And in order to ensure the necessary microclimate between the insulation and the wall, several holes are drilled into the bottom of the wall. 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 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 for external insulation
Placing a vapor barrier on the outside of a wall is a more serious mistake, especially if the walls inside the room are not protected by this same vapor barrier.
The timber 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 finishing (9);
- vapor barrier (8);
- wooden wall (6);
- insulation (4);
- waterproofing (3);
- ventilation gap (2);
- external finishing (1).
Using insulation with low vapor permeability
Using insulation with low vapor permeability when insulating walls outside, such as extruded polystyrene foam boards, will be equivalent to placing a vapor barrier on the wall. Such material will prohibit moisture on a wooden wall and will contribute to rotting.
Insulation with equivalent or greater vapor permeability than wood is 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 greatly hampered, and moisture will condense either inside the insulation, or, even worse, on a wooden wall with all the ensuing consequences.
You may also be interested:
- 8 mistakes during construction frame houses(photo)
- The cheaper it is to heat a house (gas, wood, electricity, coal, diesel)
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Is a vapor barrier necessary when insulating a wooden house made of timber from the outside? What is the difference between a vapor barrier and c c d top and bottom
First, I’ll 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 placed under the insulation in order to retain water vapor from inside the room, and thereby protect the insulation from getting wet. For complete tightness, the joints of the vapor barrier are taped with vapor barrier tape. As a result, vapors accumulate under the vapor barrier. To ensure that they erode and do not soak the internal lining (for example, gypsum board), a gap of 4 cm is left between the vapor barrier and the internal lining. The gap is ensured by laying the sheathing.
The insulation on top is protected from getting wet. waterproofing material. If the vapor barrier under the insulation is laid according to all the rules and is perfectly 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 operation of the roof, a ventilation gap is created between the waterproofing and the insulation. Because even the slightest, invisible 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 the water vapor accumulated under the waterproofing. To prevent this wetting of the insulation, as well as for the vapors to erode, there must be a ventilation gap of 2-4 cm between the waterproofing and the insulation.
Now let's look at the structure of your roof.
Before you laid insulation 9, as well as vapor barrier 11 and gypsum board 12, water vapor accumulated under vapor barrier 8, there was free access of air from below and they evaporated, so you did not notice them. Up to this point, you essentially had the correct roof design. 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) became noticeable to you. A few days later, you laid vapor barrier 11 under this insulation and sewed up gypsum board 12. If you laid the lower vapor barrier 11 according to all the rules, namely with an overlap of at least 10 cm and taped all joints with vapor-proof tape, then water vapor will not penetrate into the roof structure and will not the insulation will be soaked. But before this lower vapor barrier 11 was laid, insulation 9 had to dry out. If it has not had time to dry, then there is a high probability of mold forming in the insulation 9. This also 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 to accumulate under the vapor barrier 8, soaking the insulation and promoting the formation of fungus in it. Therefore, in an amicable way, you need to completely remove the vapor barrier 8, and make a ventilation gap of 4 cm between the vapor barrier 11 and the gypsum board 12, otherwise the gypsum board will get wet and bloom over time.
Now a few words about waterproofing. First, roofing felt is not intended for waterproofing pitched roofs; it is a bitumen-containing material and in extreme heat the bitumen will simply flow down to the roof overhang. In simple words, roofing felt will not last long in a pitched roof, it’s hard to even say how long, but I don’t think it will last more than 2 - 5 years. Second, the waterproofing (roofing felt) was not installed 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 by the fact that the rafters are higher than the layer of insulation laid between them (the rafters in your picture are just higher), or by laying counter-lattice along the rafters. Your waterproofing is laid on the sheathing (which, unlike the counter-lattice, lies across the rafters), so all the moisture that accumulates under the waterproofing will soak the sheathing and it will also not last long. Therefore, in an amicable way, the top of the roof also needs to be redone: replace the roofing felt with a waterproofing film, and 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.
One of the last stages of working with gypsum boards is joining and sealing the seams of the sheets. This is a rather difficult and responsible moment, because improper installation jeopardizes the reliability and durability of your entire new, just made repair - cracks may appear in the wall at the seams. It not only spoils appearance, but also negatively affects the strength of the wall. Therefore, beginners have a lot of doubts about joining sheets of drywall. The most important issue is the gap between the sheets of drywall. But more on that later, but now let’s figure out how to join the sheets together.
Types of longitudinal edges of a plasterboard sheet
Each sheet of drywall has two types of edges: transverse and longitudinal. The first one is not of particular interest to us now - it is always straight, without a layer of cardboard and paper, and for all types of drywall, including waterproof and fire-resistant. It happens longitudinally:
- Straight (PC markings can be seen on the sheet). This edge does not provide for sealing the joint and is more suitable for “black” finishing. Most often it is present not on drywall, but on sheets of gypsum fiber
- Semicircular, thinned on the front side (marking – PLUK). It occurs much more often than others. Sealing seams - putty, using serpyanka
- Beveled (its marking is UK). Enough labor-intensive process sealing seams in three stages. Required condition– treatment with serpyanka. Second most popular drywall edge
- Rounded (marking of this type is ZK). No joint tape required during installation
- Semicircular (marked on the sheet - PLC). Work will be required in two stages, but without serpyanka, with the condition that the putty will be of good quality
- Folded (marking of such sheets is FC). More common on gypsum fiber sheets, like straight edge
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These options can be found in stores. The most common are sheets with PLUK and UK edges. Their main advantage is that there is no need to treat the seams additionally before applying putty.
During the repair, you will need to cut sheets to a given size. In this case, you also need to make an edge - thin the sheet in the right place. This is done with a specially designed tool that removes unnecessary plaster and creates the necessary relief. If of this instrument If you don't have it at hand, use a wallpaper knife, it should be sharp. Remove a couple of millimeters, maintaining an angle of forty-five degrees.
The most important question for beginners is whether to leave a gap between sheets of drywall? Yes, after all plasterboard sheets, like any other material, tends to expand from heat and swell from moisture. The gap in this situation will help prevent the deformed sheet from leading the rest.
How to properly join drywall
As in any other job, you need to know a certain technology. The first thing you should not forget about is that under no circumstances should you do docking in weight. The place where the edges are joined must be where the frame is located. This applies to all types of docking. Secondly, the arrangement of cut and whole sheets should alternate, as in chess.
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When fastening in two layers, it is necessary to shift the sheets of the second layer by 60 cm in relation to the first. You should start with half, cut along a line running along the sheet.
If the joint is located in a corner, one sheet is attached to the profile, then the second is attached to the one standing next to it. Only later on external corner wear a specially designed one for this purpose perforated corner. The internal one is simply covered with putty. The gap should not exceed 10 mm.
How much gap should be left between sheets of drywall during a normal connection? Experts say that it should be about 7 mm, between the ceiling and the gypsum board - no more than 5, and between the floor and drywall - a gap of 1 cm.
How to seal joints
After joining, there is one more important part left - sealing the seams. Putty will help us with this. Following the instructions, dilute the gypsum base in water. In order for your repair to be durable and reliable, you first need to take care of the quality of the seams, and therefore the putty itself. In addition to it, we need a spatula, regular one will do construction 15 cm.
