Aerated concrete blocks very popular for construction residential buildings, dachas and households. buildings During construction, there is a clear saving on the price of the wall itself, on insulation and finishing, and perhaps even on the foundation... Many consider porous concrete to be the most suitable materials for home. But not everything is so simple and unambiguous. Let’s consider what negatives users found in aerated concrete based on operating experience, and what experts point out.
Aerated concrete is universal and inexpensive
Factory aerated concrete produced in an autoclave has a very exact dimensions, known characteristics, is also environmentally friendly - it does not highlight anything. For the construction of walls of residential buildings, grades D400 (400 kg/m3) and D500 are usually used.
Precision manufacturing allows you to apply a thin layer of glue when laying and make the wall surface almost flat. It is enough to apply fairly thin and cheap layers of plaster on the wall. But if the vertical joints in the masonry were not filled (usually), then to prevent increased air permeability, it is necessary to have plaster on both sides, usually 10 mm thick.
Aerated concrete is very light. Therefore, a foundation can be designed with less bearing capacity, which should also be cheaper, it seems...
The walls may not be insulated
D400 is less durable, but more heat-saving. So, for the climate of the Moscow region, if the humidity of the block is not increased, and the masonry is made at thin layer glue or on a heat-saving solution, then the thickness of the wall made of it, which meets the heat-saving requirements, will be only 46 cm. That is. actually the length of one block.
For the D500, this value is actually already about 63 cm.
But, as you know, heat loss at home should not generally exceed certain standard values. Even standards allow increased heat leakage through some structures, provided that they are compensated by increased thermal insulation in other places.
Therefore, if everything is in order with the thermal insulation measures on windows and doors, floors, foundations and roofs, and the ventilation of the building is in accordance with the standards, then insulation of aerated concrete walls large thickness, - the event is not economically profitable.
The absence of an insulating layer is a very significant saving compared to cold materials for building walls.
In addition, a single-layer wall is simpler and cheaper, more trouble-free not only in construction, but also in maintenance; during operation, you do not need to expect surprises from it, in the form of shedding or wetting of the insulation...
The foundation you need is not cheap
The foundation may have a lower load-bearing capacity, but is much more rigid than for brick. Does not allow bending. In fact, it is even more expensive than usual. Aerated concrete is very fragile, and a crack in the wall due to improper laying with the formation of local stress, especially when installing lintels and reinforced belts, is a common occurrence.
Moreover, movement of the foundation is unacceptable. Requires an expensive tape reinforced concrete foundation increased rigidity- only he can save the situation and prevent cracks from appearing. Its design and dimensions are specified in the project, but it is by no means cheap...
The need for proper masonry and use of armored belts
The fact that the creation of point stresses, for example, from a beam above a window, can lead to the destruction of a wall made of aerated concrete has already been said. It is necessary to involve only competent specialists for construction in order to avoid too costly mistakes.
Also, to avoid point loads, it is necessary to create reinforced belts, for example, create a concrete belt for beams attic floor. And also competent thermal insulation of this concrete. All this is quite complicated and not cheap.
In addition, the strength of aerated concrete, as a rule, even with an armored belt, is not enough to support heavy rigid concrete floors. Only wooden beams are possible.
Difficult to use
The issue of external plaster or additional insulation is not so simple. If the plaster crumbles or cracks, then blow-out may occur in masonry with empty vertical joints. Residents will not understand why it is cold.
The second question is not correct selection by vapor permeability. Aerated concrete itself is very vapor-transparent, so the outer layer on such a wall should have less vapor permeability than the masonry itself, otherwise the blocks will get wet.
If external plaster(insulation) and paint, for some reason, or due to its own poor quality, will have great resistance to the movement of steam, then a very serious problem will arise. And the residents again won’t know about it. So there is a risk of artificially creating moisture accumulation in the material...
Risk of destruction by water
The material is quickly destroyed by water. Wet wall made of aerated concrete cannot exist for a long time. This is aggravated by freezing. Violation of horizontal waterproofing on the foundation (basement), capillary suction of water into the masonry from the ground - and how to save the house is not yet known...
- If the roof is damaged, there may be a water leak and a wet wall not noticed in time...
- Violation of vapor exchange, due to an incorrect outer layer, as indicated, can lead to detrimental consequences...
- Humidification by precipitation in the appropriate seasons, with unreliable façade finishing...
In general, the thoroughness of waterproofing measures during construction and during operation should be the highest. You need to monitor the condition of the walls... Will it be possible to keep all the walls dry?
Difficulty hanging anything
Everyone is accustomed to the fact that the heating boiler is “hanging”, half kitchen set- hung on the wall, boiler - “well, it’s not worth it.” But how to do this when the walls and partitions are made of porous lightweight material, like pumice?
There are special dowels for fixing to aerated concrete. But they are more expensive. And the fastening cannot be called reliable.
As a result, for heavy objects, either a metal frame is placed on the wall and everything is hung on it, or a couple more sheets of cement particle board are glued to this wall...
A nail that doesn't stay in the wall is a problem and not a convenience.
Something needs to create heat capacity
Aerated concrete is too light and practically does not accumulate heat. But the house must have temperature stability. It's extremely uncomfortable without her. In a brick house, comfort is achieved by using a large array of heavy materials. And no matter how the temperature outside changes overnight, no matter how much the door is opened, everything in the house is stable.
In houses made of SIP panels, this function is performed by heated ventilation.
But what to do in aerated concrete? Don't resort to expensive but untrustworthy fans made from frame houses. It remains to place tens of tons of concrete in a heated floor, for example, or in massive interior partitions. In general, there is one more “but” that needs to be solved...
What is the durability of aerated concrete?
WITH brick house everything is clear - he is, relatively speaking, “eternal.” And they don’t give any guarantee for aerated concrete... There are no known facts that the manufacturer guarantees anything and promises to fix it if problems arise.
There are already more and more reviews that aerated concrete is starting to crumble. The service life of a wall under load is a maximum of 40 years for high-quality factory-made aerated concrete in a frosty climate... There are many such reviews, and entire aerated concrete walls older than 50 years are found only in places where the temperature does not go beyond 0. Probably various disadvantages, which were mentioned above, together, plus the state of stress under load with changes in humidity and freezing, leads to the fact that the blocks are covered with a web of cracks. Which only diverge over time.
However, this material is still considered new, and extensive experience of its long-term operation has not been accumulated with clear conclusions. But there is no refutation of the above data yet...
Dew point in the wall - the temperature zone in which water vapor condenses and turns into water.
The dew point is highly dependent on air humidity, and the higher the humidity, the higher the likelihood of condensation.
The dew point is also affected by the temperature difference between inside and outside the room.
In this review, we are testing to find the dew point in a wall made of D500 aerated concrete. Will be considered different variants walls made of aerated concrete, for example, 200mm and 400mm thick, as well as using insulation.
What is the dew point in a wall
Calculations were carried out in the program teploraschet.rf
Density of aerated concrete 500 kg/m³ (D500).
Black line on the graph shows the temperatures inside the aerated concrete wall. Starting from 20 degrees Celsius and ending with -20 degrees.
Blue line shows the dew point temperature. If the temperature line touches the dew point line, a condensation zone is formed.
In other words, if the dew point temperature is always lower than the temperature in the aerated concrete, then condensation will not form.
As can be seen in the graph, the dew point in both cases is inside the aerated concrete, closer to the outside, and the amount of condensate is almost equal.
Aerated concrete and mineral wool (outside)
Now let’s look at what happens in aerated concrete if it is insulated with mineral wool from the outside.
| Aerated concrete D500 200mm + 50mm mineral wool | Aerated concrete D500 200mm + 100mm mineral wool |
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Option for insulating aerated concrete mineral wool(100mm) eliminates condensation. Moreover, there will be no condensation even if the temperature in the house is +25 and -40 outside. Moreover, 100mm mineral wool provides very good thermal insulation.
Aerated concrete and mineral wool (inside)
| 50mm mineral wool + aerated concrete D500 200mm | 100mm mineral wool + aerated concrete D500 200mm |
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As can be seen in the graph, internal insulation mineral wool leads to significant condensation formation throughout the thickness of the aerated concrete wall.
Note interesting feature- the thicker inner layer mineral wool, the more condensate forms in the aerated concrete wall, which is extremely undesirable.
Important! Wet aerated concrete retains heat less well and breaks down faster.
Conclusion
It is better to keep the dew point in an aerated concrete wall closer to the outside. And it’s even better if the dew point is in the insulation, be it mineral wool or polystyrene foam. Note that polystyrene foam is not afraid of getting wet, and does not lose its thermal insulation properties, and mineral wool, when wet, greatly loses its properties as insulation.
Now very often the facade is insulated with mineral wool and covered with it facing bricks, leaving a ventilation gap that dries the mineral wool. Another popular method is plastered foam, which is much cheaper.
The question of the need to insulate walls made of aerated concrete arises due to the fact that in most regions, due to low winter temperatures, the thermal resistance of this material is not sufficient for standard values.
In addition, as a result of the phenomenon of moisture condensation in the thickness of aerated concrete, its thermal resistance is further reduced and its service life is reduced.
To understand the condensation of water in a wall, let’s remember what’s actually happening in it. Water in nature can have three states. This is a liquid state - rivers, seas and oceans, water in a water supply system, - a solid state - snow and glaciers - and also a gaseous state - this is moisture vapor in the air. Water vapor is not clouds or fog, it is water molecules contained along with other gas molecules in the air. And clouds and fog are moisture that has already condensed from the air.
Almost any wall of a residential building has a certain breathability, which indicates that there is air in its thickness. And since air is present, water vapor is also present with it. And these vapors, these water molecules tend to move to where it is freer, where the air humidity is lower.
Thus, there is a constant movement of these moisture vapors through the walls. In winter, when the humidity of the outside air is low, water vapor moves in the air of the wall from the inside to the outside. And in the summer, if the humidity of the outside air rises so much that it becomes higher than the humidity inside the house - on the contrary, from outer surface walls inward.
This is the process called wall breathing. This should not be confused with air movement through walls. The air in the wall is practically motionless, since Atmosphere pressure the same both in the house and outside.
Let us now remember what the dew point is, that is, the temperature at which water vapor in a saturated state begins to precipitate in the form of condensate and turns from a gaseous state to a liquid one. This dew point depends primarily on the saturation of the air with water vapor, which can be seen in this video.
Examples of wall insulation with calculation graphs are shown in the attached video. It is clear that these calculations did not take into account other structural elements, plasters, membranes and cladding, it was only important to compare various insulation materials in their use with aerated concrete.
But it was especially important to understand how the vapor permeability coefficient of the insulation affects its performance. And all these examples fully confirm the construction rule multilayer wall: the vapor permeability coefficient of each layer should increase in the direction from the inner surface of the structure to the outer.
And one more thing about hydration. We just saw that it is impossible to completely avoid wetting the wall, as such. Various insulation materials behave differently, but each has the outside air temperature at which condensation inevitably begins to form in the wall.
And you need to choose a design in which this moisture would be the least at minimum temperatures in the region. The less moisture accumulation in the wall over time winter period, the easier and faster wall will dry out with the onset summer season. And of course, do not forget about the standard thermal resistance in the region of development.
Aerated concrete blocks - due to their porous structure, have very high characteristics, such as thermal insulation material, but despite this, during construction from cellular concrete and it is advisable to insulate the walls made of aerated concrete. Even if you have to spend money on additional heat insulation, it will pay off for you thanks to reduced energy consumption in the future to maintain a constant temperature in the house. Using aerated concrete adhesive is also very effective solution. But additional insulation houses made of aerated concrete, it will also not be amiss.
Choosing material for home insulation
For a house built from aerated concrete blocks, you need to select the right material for insulation. As with choosing any building materials for the home, you need to choose only high-quality ones from reliable and reputable manufacturers. For a house made of aerated concrete, there is a wide range heat-insulating materials. At first glance, it may seem that figuring out and choosing the right insulation for your home is quite difficult.
We recommend consulting with consultants working in this area; the thing is that the choice largely depends on the area in which you live, what the average annual temperature and humidity are. Depending on this, you select suitable insulation for the house, its thickness.
House insulation work
Before you start insulating the house from the outside, you need to carefully check the quality of all the seams between the blocks and on the walls of the house. Also check out the finishing of aerated concrete walls.
Insulation of a house made of aerated concrete
Adviсe:
- Usage masonry adhesive for aerated concrete blocks, allows significantly reduce seams between blocks, and this in turn will lead to a reduction in heat loss.
- If any problems with seams, voids or anything else are found, we recommend using construction foam to eliminate them. After that, carefully putty and start insulating.
- Insulation of the house from the outside can be combined with insulation of the house from the inside, in order to be confident in the quality of the thermal insulation of your house.
Dew point in the wall
When is it produced? insulation of aerated concrete house, it is important to remember such a concept as Dew point in the wall. If there is no insulation, then this point is located in the thickness of the material; when the walls are thermally insulated, the point moves towards the heat insulator.
Due to this, very important use all finishing and heat-insulating building materials with high coefficient vapor permeability.
This allows moisture to escape without causing it to remain trapped inside. If any difficulties arise, you need to use ventilated facades. They effectively help cope with excess moisture and get rid of it.
On this moment, there are a huge number of types of ventilated facades for houses made of aerated concrete blocks, for every taste and color, wood, brick and artificial stone.