The thickness of the outer walls is chosen according to the largest of the values obtained as a result of static and heat engineering calculations, and is assigned in accordance with the design and heat engineering features of the enclosing structure.
In prefabricated concrete housing construction, the estimated thickness outer wall are linked to the nearest larger value from a unified series of outer wall thicknesses adopted in the centralized manufacture of molding equipment 250, 300, 350, 400 mm for panel and 300, 400, 500 mm for large-block buildings.
The calculated thickness of the stone walls is coordinated with the dimensions of the brick or stone and is taken equal to the nearest greater structural thickness obtained during masonry. With brick dimensions of 250 × 120 × 65 or 250 × 120 × 88 mm (modular brick), the thickness of the walls of solid masonry is 1; 1.5; 2; 2.5 and 3 bricks (taking into account vertical joints of 10 mm between individual stones) is 250, 380, 510, 640, and 770 mm.
The structural thickness of a wall made of sawn stone or lightly concrete small blocks, the unified dimensions of which are 390 × 190 × 188 mm, when laid in one stone is 390 and in 1.5 - 490 mm.
The design of walls is based on the comprehensive use of the properties of the materials used and solves the problem of creating required level strength, stability, durability, insulating and architectural and decorative qualities.
In accordance with modern requirements for the economical use of materials, when designing low-rise residential buildings with stone walls, they try to use maximum amount local building materials. For example, in areas remote from highways, small locally produced stones or monolithic concrete are used to build walls in combination with local heaters and on local aggregates, which require only imported cement. In settlements located near industrial centers, houses are designed with walls made of large blocks or panels manufactured at the enterprises of this region. At present, stone materials are being increasingly used in the construction of houses in garden plots.
When designing low-rise buildings, two schemes for the constructive solution of external walls are usually used - solid walls made of homogeneous material and lightweight multilayer walls made of materials of different densities. For the construction of internal walls, only solid masonry is used. When designing external walls according to the solid masonry scheme, preference is given to less dense materials. This technique allows you to achieve the minimum thickness of the walls in terms of thermal conductivity and more fully use the load-bearing capacity of the material. Construction Materials high density is advantageous to use in combination with low density materials (lightweight walls). The principle of lightweight walls is based on the fact that the bearing functions are performed by a layer (layers) of high-density materials (γ> 1600 kg / m 3), and a low-density material serves as a heat insulator. For example, instead of a solid outer wall made of clay bricks 64 cm thick, you can use a lightweight wall structure made of a layer of the same brick 24 cm thick, with a fiberboard insulation 10 cm thick. Such a replacement leads to a decrease in wall weight by 2.3 times.
For the manufacture of walls of low-rise buildings, artificial and natural small stones are used. Currently, artificial firing stones are used in construction (clay brick, solid, hollow, porous and ceramic blocks); non-fired stones (silicate brick, hollow blocks of heavy concrete and solid blocks of lightweight concrete); natural small stones - torn rubble, sawn stones (tuff, pumice, limestone, sandstone, shell rock, etc.).
The size and weight of the stones are designed in accordance with the manual laying technology and taking into account the maximum mechanization of work. The walls are laid out of stones with filling the gap between them with mortar. Most often, cement-sand mortars are used. For laying internal walls, ordinary sand is used, and for external walls, sand of low density (perlite, etc.). Wall laying is carried out with obligatory observance suture dressing(4.6) in series.
As already noted, the width of the masonry wall is always a multiple of the number of halves of the brick. Rows facing the front surface of the masonry are called front verst, and facing the inside - inner verst. The rows of masonry between the inner and front mile are called backfill. Bricks laid long side along the wall form spoon row, and laid across the walls - bonder row. masonry system(4.7) is formed by a certain arrangement of stones in the wall.
The row of masonry is determined by the number of spoon and bond rows. With a uniform alternation of spoon and bond rows, a two-row (chain) masonry system is obtained (Fig. 4.5b). A less labor-intensive multi-row masonry system, in which one row of bricks binds five spoon rows (Fig. 4.5a). In the walls of small blocks erected according to a multi-row system, one row of bonders binds two rows of spoon masonry (Fig. 4.5c).
Fig.4.5. Types of manual laying of walls: a) - multi-row brickwork; b) - chain brickwork; c) - multi-row masonry; d) - chain masonry
Solid masonry of high density stones is used only for the construction of internal walls and pillars and external walls of unheated premises (Fig. 4.6a-g). In some cases, this masonry is used for the construction of external walls in a multi-row system (Fig. 4.6a-c, e). The two-row stone laying system is used only when necessary. For example, in ceramic stones, it is recommended to place void gaps across the heat flow in order to reduce the thermal conductivity of the wall. This is achieved with a chain laying system.
Lightweight external walls are designed in two types - with insulation between two walls of solid masonry or with an air gap (Fig. 4.6i-m) and with insulation lining the solid masonry wall (Fig. 4.6n, o). In the first case, there are three main structural options for walls - walls with horizontal outlets of anchor stones, walls with vertical stone diaphragms (well masonry) and walls with horizontal diaphragms. The first option is used only in cases where lightweight concrete is used as a heater, which monolithizes anchor stones. The second option is acceptable for insulation in the form of pouring lightweight concrete and laying thermal liners (Fig. 4.6k). The third option is used for insulation from bulk materials (Fig. 4.6l) or from lightly concrete stones. Solid masonry walls with an air gap (Fig. 4.6m) also belongs to the category of lightweight walls, since the closed air gap acts as a layer of insulation. It is advisable to take the thickness of the interlayers equal to 2 cm. An increase in the interlayer practically does not increase its thermal resistance, and a decrease sharply reduces the effectiveness of such thermal insulation. More often, the air gap is used in combination with insulation boards (Fig. 4.6k, o).
Fig. 4.6, Variants of manual laying of the walls of low-rise residential buildings: a), b) - solid outer walls made of bricks; c) - a solid internal brick wall; e), g) - solid outer walls made of stones; d), f) - solid internal walls from stones; i)-m) - lightweight walls with internal insulation; n), o) - lightweight walls with external insulation; 1 - brick; 2 - plaster or cladding with sheets; 3 - artificial stone; 4 - slab insulation; 5 - air gap; 6 - vapor barrier; 7 - wooden antiseptic rail; 8 - backfill; 9 - solution diaphragm; 10 - lightweight concrete; 11 - natural frost-resistant stone
To insulate stone walls from the side of the street, a rigid slab insulation made of lightweight concrete, foam glass, fiberboard is used in combination with a weather-resistant and durable cladding (asbestos cement sheets, boards, etc.). The option of wall insulation from the outside is effective only if there is no access of cold air to the zone of contact between the carrier layer and the insulation layer. To insulate the outer walls from the side of the room, a semi-rigid slab insulation (reed, straw, mineral wool, etc.) is used, located close to the surface of the first or with the formation of an air gap, 16–25 mm thick - “at a distance”. Slabs "at a distance" are attached to the wall with metal zigzag brackets or nailed to wooden antiseptic slats. The open surface of the insulation layer is covered with sheets of dry plaster. Between them and the insulation layer, a vapor barrier layer of glassine, polyethylene film, metal foil, etc. is necessarily placed.
Study and analyze the above material and answer the proposed question.
Question 4.2. Can rows of bricks laid long side along a wall be called poke rows?
4.2. answer: yes
The appearance of the facades of buildings, first of all, is formed by the walls. Therefore, stone walls must meet the relevant aesthetic requirements. In addition, the walls are subject to numerous force, humidity and other influences: their own weight, loads from ceilings and roofs, wind, seismic shocks and uneven deformation of the bases, solar radiation, variable temperature and precipitation, noise, etc. Therefore, the walls must meet the strength requirements , durability, fire resistance, protect the premises from adverse external influences, provide them with a favorable temperature and humidity regime for comfortable living and working.
The wall construction complex often includes window and door opening fillings, other structural elements, which must also meet the specified requirements.
According to the degree of spatial rigidity, buildings with stone walls can be divided into buildings with a rigid structural scheme, which include buildings with a frequent arrangement of transverse walls, i.e. predominantly civil buildings, and buildings with an elastic structural scheme, which include one-story industrial, warehouse and other similar buildings (in which the longitudinal walls have a significant height and large distances between the transverse walls).
Depending on the purpose of the building or structure, acting loads, number of storeys and other factors, stone walls are divided into:
The strength of stone walls to a large extent depends on the strength of the masonry:
where A is a coefficient depending on the strength of the stone; R K- the strength of the stone; Rp- the strength of the solution.
In accordance with this, even if the strength of the mortar is equal to 0, the masonry will have a strength equal to 33% of its maximum possible strength.
To ensure joint work and the formation of a space box, the walls are usually connected to each other, to the floors and the frame using anchors. Therefore, the stability and rigidity of stone walls depend not only on their own rigidity, but also on the rigidity of ceilings, coatings and other structures that support and fix the walls along their height.
Walls are solid (without openings) and with openings. Solid walls without structural elements and architectural details are called smooth. There are the following structural elements of the walls (Fig. 7.1):
Rice. 7.1. Structural elements of the walls: a - pilasters; b - buttresses; in - pylons; g - masonry edge; d - belt; e - sandrik; g - cornice; h - furrows; and - niches; to - piers; l - lintels; m - wooden plugs
Wall laying is carried out with obligatory dressing of vertical seams. On the outside of the wall, the rows of masonry can alternate as follows:
In practice, systems with alternating spoon and bonder rows are most widely used. The more adjacent rows of spoons, the less durable the masonry is (but also less laborious), since the number of longitudinal vertical rows increases and the number of bricks that are split into pieces decreases. Therefore, when choosing a masonry dressing system, they are guided by these indicators. Bandaging systems for stone walls, shown in fig. 7.2.
Rice. 7.2. Systems for dressing the laying of stone walls: a, b, c, d - single-row, respectively chain, cross, Dutch, Gothic; d - two-row English; e - two-row with plug-in pokes; g - three-row; h - five-row; and - a section of the wall with a five-row dressing; j - wall incision with single-row dressing
[ outdoor house walls, technology, classification, bricklayer, design and masonry bearing walls ]
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The designs of the outer walls are extremely diverse; they are determined by the construction system of the building, the material of the walls and their static function.
Fig. 2. Expansion joints
Fig. 3. Details of the installation of expansion joints in brick and panel buildings
Thermal shrinkage seams arrange in order to avoid the formation of cracks and distortions caused by the concentration of forces from exposure to variable temperatures and shrinkage of the material (masonry, monolithic or prefabricated concrete structures, etc.). Temperature-shrinkage joints cut through the structures of only the ground part of the building. The distances between the temperature-shrinkage seams are assigned in accordance with climatic conditions and physical and mechanical properties wall materials. For external walls made of clay bricks on a mortar of grade M50 and more, the distances between temperature-shrinkage joints of 40-100 m are taken according to SNiP "Stone and reinforced masonry structures", for external walls made of concrete panels 75-150 m according to VSN32-77, Gosgrazhdanstroy "Instruction on the design of structures of panel residential buildings. At the same time, the smallest distances refer to the most severe climatic conditions.
In buildings with longitudinal load-bearing walls, seams are arranged in the area of adjacency to transverse walls or partitions; in buildings with transverse load-bearing walls, seams are often arranged in the form of two paired walls. The smallest joint width is 20 mm. The seams must be protected from blowing, freezing and through leaks with the help of metal compensators, sealing, and insulating liners. Examples of constructive solutions for temperature-shrinkage joints in brick and panel walls are given in fig. 3.
Sedimentary seams should be provided in places of sharp differences in the number of storeys of the building (sedimentary seams of the first type), as well as in case of significant uneven deformation of the base along the length of the building, caused by the specifics of the geological structure of the base (sedimentary seams of the second type). Sedimentary joints of the first type are appointed to compensate for differences in vertical deformations of ground structures of the high and low parts of the building, and therefore they are arranged similarly to temperature-shrinkage joints only in ground structures. The design of the seam in frameless buildings provides for the installation of a sliding seam in the zone of support of the ceiling of the low-rise part of the building on the walls of the high-rise building, in frame buildings - the hinged support of the crossbars of the low-rise part on the columns of the high-rise building. Sedimentary seams of the second type cut the building to its entire height - from the ridge to the base of the foundation. Such seams in frameless buildings are designed in the form of paired transverse walls, in frame buildings - paired frames. The nominal width of settlement joints of the first and second types is 20 mm. Design features of earthquake-resistant buildings, as well as buildings under construction on subsidence, undermining and permafrost soils, are considered in a separate section.
Fig. 4. Exterior wall views
External wall structures classified according to:
According to the static function, load-bearing, self-supporting or non-bearing wall structures are distinguished (Fig. 4). D
Carriers walls, in addition to the vertical load from their own mass, transmitting loads to the foundations from adjacent structures: ceilings, partitions, roofs, etc.
Self-supporting walls perceive the vertical load only from their own mass (including the load from balconies, bay windows, parapets and other wall elements) and transfer it to the foundations directly or through plinth panels, randbalki, grillage or other structures.
Table 11 - brick; 2 - small block; 3, 4 - insulation and air gap; 5 - lightweight concrete; 6 - autoclaved cellular concrete; 7 - constructive heavy or light concrete; 8 - log; 9 - caulk; 10 - timber; eleven - wooden frame; 12 - vapor barrier; 13 - airtight layer; 14 - sheathing from boards, waterproof plywood, chipboard or others; 15 - sheathing from inorganic sheet materials; 16 - metal or asbestos-cement frame; 17 - ventilated air gap
External walls can be single layer or layered designs. Single layer walls erected from panels, concrete or stone blocks, cast-in-place concrete, stone, brick, wooden logs or beams. In layered walls, the performance of various functions is assigned to various materials. Strength functions provide concrete, stone, wood; durability functions - concrete, stone, wood or sheet material ( aluminum alloys, enamelled steel, asbestos cement, etc.); thermal insulation functions - effective heaters (mineral wool boards, fibrolite, expanded polystyrene, etc.); vapor barrier functions - rolled materials (roofing felt, foil, etc.), dense concrete or mastics; decorative functions - various facing materials. An air gap can be included in the number of layers of such a building envelope. Closed - to increase its resistance to heat transfer, ventilated - to protect the room from radiation overheating or to reduce deformations of the outer facing wall.
Structures of single and multilayer walls can be made prefabricated or in traditional technique.
The main types of structures of external walls and their areas of application are given in Table. one.
The purpose of the static function of the outer wall, the choice of materials and structures is carried out taking into account the requirements of SNiP "Fire-prevention standards for the design of buildings and structures". According to these standards, load-bearing walls, as a rule, must be fireproof. The use of slow-burning load-bearing walls (for example, wooden plastered) with a fire resistance limit of at least 0.5 hours is allowed only in one-two-story houses. The fire resistance limit of fireproof wall structures must be at least 2 hours, and therefore they must be made of stone or concrete materials. High requirements for the fire resistance of load-bearing walls, as well as columns and pillars, are due to their role in the safety of a building or structure. Fire damage vertical load-bearing structures can lead to the collapse of all structures based on them and the building as a whole.
Non-load-bearing external walls are designed to be fireproof or slow-burning with significantly lower fire resistance limits (0.25-0.5 h), since the destruction of these structures from exposure to fire leads only to local damage to the building.
Fireproof non-bearing external walls should be used in residential buildings above 9 floors, with a lower number of storeys, the use of fire-retardant structures is allowed.
The thickness of the outer walls is chosen according to the largest of the values obtained as a result of static and heat engineering calculations, and is assigned in accordance with the design and heat engineering features of the enclosing structure.
In prefabricated concrete housing construction, the calculated thickness of the outer wall is linked to the nearest larger value from the unified series of outer wall thicknesses adopted in the centralized manufacture of molding equipment 250, 300, 350, 400 mm for panel and 300, 400, 500 mm for large-block buildings.
The calculated thickness of the stone walls is coordinated with the dimensions of the brick or stone and is taken equal to the nearest greater structural thickness obtained during masonry. With brick dimensions of 250X120X65 or 250X X 120x88 mm (modular brick), the thickness of the walls of solid masonry is 1; 1 1/2; 2; 2 1/2 and 3 bricks (taking into account vertical joints of 10 mm between individual stones) is 250, 380, 510, 640 and 770 mm.
The structural thickness of a wall made of sawn stone or lightweight concrete small blocks, the unified dimensions of which are 390X190X188 mm, when laying in one stone is 390 and in 1/2 g - 490 mm.
The thickness of walls made of non-concrete materials with effective heaters in some cases, they take more than that obtained by thermal engineering due to design requirements: an increase in the size of the wall section may be necessary for reliable insulation of joints and mates with filling openings.
The construction of walls is based on the comprehensive use of the properties of the materials used and solves the problem of creating the required level of strength, stability, durability, insulating and architectural and decorative qualities.
4
4.1.
aboutreply: Yes(file address Block 3) Your answer is correct, because walls are load-bearing only when they take the load from their own weight and from other structural elements of the building. Go to question 4.2
4
4.1.
aboutreply: NO(file address Block 3) Your answer is INCORRECT because YOU did not take into account that walls that do not take the load from other elements of the building are classified as either self-supporting or non-bearing. Return to reading the text
The thickness of the outer walls is chosen according to the largest of the values obtained as a result of static and heat engineering calculations, and is assigned in accordance with the design and heat engineering features of the enclosing structure.
In prefabricated concrete housing construction, the calculated thickness of the outer wall is linked to the nearest larger value from the unified series of outer wall thicknesses adopted in the centralized manufacture of molding equipment 250, 300, 350, 400 mm for panel and 300, 400, 500 mm for large-block buildings.
The calculated thickness of the stone walls is coordinated with the dimensions of the brick or stone and is taken equal to the nearest greater structural thickness obtained during masonry. With brick dimensions of 250 × 120 × 65 or 250 × 120 × 88 mm (modular brick), the thickness of the walls of solid masonry is 1; 1.5; 2; 2.5 and 3 bricks (taking into account vertical joints of 10 mm between individual stones) is 250, 380, 510, 640, and 770 mm.
The structural thickness of a wall made of sawn stone or lightly concrete small blocks, the unified dimensions of which are 390 × 190 × 188 mm, when laid in one stone is 390 and in 1.5 - 490 mm.
The construction of walls is based on the comprehensive use of the properties of the materials used and solves the problem of creating the required level of strength, stability, durability, insulating and architectural and decorative qualities.
In accordance with modern requirements for the economical use of materials, when designing low-rise residential buildings with stone walls, they try to use the maximum amount of local building materials. For example, in areas remote from highways, small locally produced stones or monolithic concrete are used to build walls in combination with local heaters and on local aggregates, which require only imported cement. In settlements located near industrial centers, houses are designed with walls made of large blocks or panels manufactured at the enterprises of this region. At present, stone materials are being increasingly used in the construction of houses in garden plots.
When designing low-rise buildings, two schemes for the constructive solution of external walls are usually used - solid walls made of homogeneous material and lightweight multilayer walls made of materials of different densities. For the construction of internal walls, only solid masonry is used. When designing external walls according to the solid masonry scheme, preference is given to less dense materials. This technique allows you to achieve the minimum thickness of the walls in terms of thermal conductivity and more fully use the load-bearing capacity of the material. It is advantageous to use building materials of high density in combination with materials of low density (lightweight walls). The principle of lightweight walls is based on the fact that the bearing functions are performed by a layer (layers) of high-density materials (γ> 1600 kg / m 3), and a low-density material serves as a heat insulator. For example, instead of a solid outer wall made of clay bricks 64 cm thick, you can use a lightweight wall structure made of a layer of the same brick 24 cm thick, with a fiberboard insulation 10 cm thick. Such a replacement leads to a decrease in wall weight by 2.3 times.
For the manufacture of walls of low-rise buildings, artificial and natural small stones are used. Currently, artificial firing stones are used in construction (clay brick, solid, hollow, porous and ceramic blocks); non-fired stones (silicate brick, hollow blocks of heavy concrete and solid blocks of lightweight concrete); natural small stones - torn rubble, sawn stones (tuff, pumice, limestone, sandstone, shell rock, etc.).
The size and weight of the stones are designed in accordance with the manual laying technology and taking into account the maximum mechanization of work. The walls are laid out of stones with filling the gap between them with mortar. Most often, cement-sand mortars are used. For laying internal walls, ordinary sand is used, and for external walls, sand of low density (perlite, etc.). Wall laying is carried out with obligatory observance suture dressing(4.6) in series.
As already noted, the width of the masonry wall is always a multiple of the number of halves of the brick. Rows facing the front surface of the masonry are called front verst, and facing the inside - inner verst. The rows of masonry between the inner and front mile are called backfill. Bricks laid long side along the wall form spoon row, and laid across the walls - bonder row. masonry system(4.7) is formed by a certain arrangement of stones in the wall.
The row of masonry is determined by the number of spoon and bond rows. With a uniform alternation of spoon and bond rows, a two-row (chain) masonry system is obtained (Fig. 4.5b). A less labor-intensive multi-row masonry system, in which one row of bricks binds five spoon rows (Fig. 4.5a). In the walls of small blocks erected according to a multi-row system, one row of bonders binds two rows of spoon masonry (Fig. 4.5c).
Fig.4.5. Types of manual laying of walls: a) - multi-row brickwork; b) - chain brickwork; c) - multi-row masonry; d) - chain masonry
Solid masonry of high density stones is used only for the construction of internal walls and pillars and external walls of unheated premises (Fig. 4.6a-g). In some cases, this masonry is used for the construction of external walls in a multi-row system (Fig. 4.6a-c, e). The two-row stone laying system is used only when necessary. For example, in ceramic stones, it is recommended to place void gaps across the heat flow in order to reduce the thermal conductivity of the wall. This is achieved with a chain laying system.
Lightweight external walls are designed in two types - with insulation between two walls of solid masonry or with an air gap (Fig. 4.6i-m) and with insulation lining the solid masonry wall (Fig. 4.6n, o). In the first case, there are three main structural options for walls - walls with horizontal outlets of anchor stones, walls with vertical stone diaphragms (well masonry) and walls with horizontal diaphragms. The first option is used only in cases where lightweight concrete is used as a heater, which monolithizes anchor stones. The second option is acceptable for insulation in the form of pouring lightweight concrete and laying thermal liners (Fig. 4.6k). The third option is used for insulation from bulk materials (Fig. 4.6l) or from lightly concrete stones. Solid masonry walls with an air gap (Fig. 4.6m) also belongs to the category of lightweight walls, since the closed air gap acts as a layer of insulation. It is advisable to take the thickness of the interlayers equal to 2 cm. An increase in the interlayer practically does not increase its thermal resistance, and a decrease sharply reduces the effectiveness of such thermal insulation. More often, the air gap is used in combination with insulation boards (Fig. 4.6k, o).
Fig. 4.6, Variants of manual laying of the walls of low-rise residential buildings: a), b) - solid outer walls made of bricks; c) - a solid internal brick wall; e), g) - solid outer walls made of stones; d), f) - solid internal walls made of stones; i)-m) - lightweight walls with internal insulation; n), o) - lightweight walls with external insulation; 1 - brick; 2 - plaster or cladding with sheets; 3 - artificial stone; 4 - slab insulation; 5 - air gap; 6 - vapor barrier; 7 - wooden antiseptic rail; 8 - backfill; 9 - solution diaphragm; 10 - lightweight concrete; 11 - natural frost-resistant stone
To insulate stone walls from the side of the street, a rigid slab insulation made of lightweight concrete, foam glass, fiberboard is used in combination with a weather-resistant and durable cladding (asbestos cement sheets, boards, etc.). The option of wall insulation from the outside is effective only if there is no access of cold air to the zone of contact between the carrier layer and the insulation layer. To insulate the outer walls from the side of the room, a semi-rigid slab insulation (reed, straw, mineral wool, etc.) is used, located close to the surface of the first or with the formation of an air gap, 16–25 mm thick - “at a distance”. Slabs "at a distance" are attached to the wall with metal zigzag brackets or nailed to wooden antiseptic slats. The open surface of the insulation layer is covered with sheets of dry plaster. Between them and the insulation layer, a vapor barrier layer of glassine, polyethylene film, metal foil, etc. is necessarily placed.
Study and analyze the above material and answer the proposed question.
The article brought to your attention is devoted to the design of the outer walls of modern buildings in terms of their thermal protection and appearance.
Considering modern buildings, i.e. buildings that currently exist should be divided into buildings designed before and after 1994. The starting point in changing the principles of constructive solutions for external walls in domestic buildings is the order of the State Construction Committee of Ukraine No. 247 of 12/27/1993, which established new standards for thermal insulation of enclosing structures of residential and public buildings. Subsequently, by order of the State Construction Committee of Ukraine No. 117 dated June 27, 1996, amendments were introduced to SNiP II -3-79 "Construction Heat Engineering", which established the principles for designing thermal insulation of new and reconstructed residential and public buildings.
After six years of the new norms, there are no longer any questions about their expediency. Years of practice showed what was done right choice which, at the same time, requires careful multilateral analysis and further development.
For buildings designed before 1994 (unfortunately, the construction of buildings according to the old thermal insulation standards is still encountered), the outer walls perform both load-bearing and enclosing functions. Moreover, the load-bearing characteristics were provided with rather insignificant thicknesses of the structures, and the fulfillment of the enclosing functions required significant material costs. Therefore, the reduction in the cost of construction followed the path of a priori low energy efficiency due to well-known reasons for an energy-rich country. This regularity applies equally to buildings with brick walls, as well as to buildings made of large-sized concrete panels. Thermally, the differences between these buildings consisted only in the degree of thermal heterogeneity of the outer walls. Masonry walls can be regarded as thermally quite homogeneous, which is an advantage, since a uniform temperature field of the inner surface of the outer wall is one of the indicators of thermal comfort. However, to ensure thermal comfort, the absolute value of the surface temperature must be sufficiently high. And for the outer walls of buildings created according to the standards before 1994, the maximum temperature of the inner surface of the outer wall at the calculated temperatures of the indoor and outdoor air could be only 12 ° C, which is not enough for thermal comfort conditions.
The appearance of the brickwork walls also left much to be desired. This is due to the fact that domestic technologies for making bricks (both clay and ceramic) were far from perfect, as a result, the brick in the masonry had different hues. Silicate brick buildings looked somewhat better. IN last years in our country there was a brick made according to all the requirements of modern world technologies. This refers to the Kor-chevatsky plant, where they produce bricks with excellent appearance and relatively good thermal insulation properties. From such products it is possible to build buildings, the appearance of which will not be inferior to foreign counterparts. Multi-storey buildings in our country were mainly built from concrete panels. This type of wall is characterized by significant thermal inhomogeneity. In single-layer expanded clay concrete panels, thermal heterogeneity is due to the presence of butt joints (photo 1). Moreover, its degree, in addition to constructive imperfection, is also significantly affected by the so-called human factor - the quality of sealing and insulation of butt joints. And since this quality was low in the conditions of the Soviet construction, the joints leaked and froze, presenting the inhabitants with all the “charms” of damp walls. In addition, the widespread non-compliance with the technology of manufacturing expanded clay concrete led to an increased density of the panels and their low thermal insulation.
Things were not much better in buildings with three-layer panels. Since the stiffening ribs of the panels caused the thermal inhomogeneity of the structure, the problem of butt joints remained relevant. The appearance of the concrete walls was extremely unpretentious (photo 2) - we did not have colored concrete, and the paints were not reliable. Understanding these problems, architects tried to give variety to buildings by applying tiles to the outer surface of the walls. From the point of view of the laws of heat and mass transfer and cyclic temperature and humidity influences, such a constructive and architectural solution is absolute nonsense, which is confirmed by the appearance of our houses. When designing
after 1994, the energy efficiency of the building and its elements became decisive. Therefore, the established principles of designing buildings and their enclosing structures have been revised. The basis for ensuring energy efficiency is strict observance of the functional purpose of each structural element. This applies both to the building as a whole and to the enclosing structures. The so-called frame-monolithic buildings confidently entered the practice of domestic construction, where the strength functions are performed by a monolithic frame, and the outer walls carry only enclosing (heat and sound insulation) functions. At the same time, preserved and successfully developed design principles buildings with load-bearing outer walls. The latest solutions are also interesting in that they are fully applicable to the reconstruction of those buildings that were considered at the beginning of the article and which require reconstruction everywhere.
The constructive principle of external walls, which can equally be used for the construction of new buildings and for the reconstruction of existing ones, is continuous insulation and insulation with an air gap. The effectiveness of these design solutions is determined by the optimal selection of the thermophysical characteristics of a multilayer structure - a load-bearing or self-supporting wall, insulation, textured layers, and an outer finishing layer. The material of the main wall can be any and the determining requirements for it are strength and load-bearing.
The thermal insulation characteristics in this wall solution are fully described by the thermal conductivity of the insulation, which is used as PSB-S expanded polystyrene, mineral wool boards, foam concrete, and ceramic materials. Styrofoam - thermal insulation material with low thermal conductivity, durable and technologically advanced when insulated. Its production has been established at domestic plants (Stirol plants in Irpen, plants in Gorlovka, Zhytomyr, Bucha). The main disadvantage is that the material is combustible and, according to domestic fire standards, has limited use (for low-rise buildings, or in the presence of significant protection from non-combustible lining). When insulating the outer walls of multi-storey buildings, PSB-S is also subject to certain strength requirements: the density of the material must be at least 40 kg / m3.
Mineral wool boards are a heat-insulating material with low thermal conductivity, durable, technologically insulating, meets the requirements of domestic fire regulations for the outer walls of buildings. In the Ukrainian market, as well as in the markets of many other European countries, mineral wool boards from ROCKWOOL, PAROC, ISOVER, etc. are used. characteristic feature of these companies is a wide range of manufactured products - from soft plates to hard ones. Moreover, each name has a strictly targeted purpose - for roof insulation, inside walls, facade insulation etc. For example, for facade wall insulation according to the considered design principles, ROCKWOOL produces FASROCK boards, and PAROC produces L-4 boards. A characteristic feature of these materials is their high dimensional stability, which is especially important for insulation with a ventilated air gap, low thermal conductivity and guaranteed product quality. In terms of thermal conductivity, these mineral wool slabs are no worse than expanded polystyrene (0.039-0.042 WDmK) due to their structure. Targeted production of plates determines the operational reliability of insulation of external walls. It is absolutely unacceptable to use mats or soft mineral wool boards for the considered design options. Unfortunately, in domestic practice there are solutions for wall insulation with a ventilated air gap, when mineral wool mats are used as a heater. The thermal reliability of such products raises serious concerns, and the fact of their rather wide application can only be explained by the lack of a system for commissioning new design solutions in Ukraine. An important element in the construction of walls with facade insulation is the outer protective and decorative layer. It not only determines the architectural perception of the building, but also determines the moisture state of the insulation, being both a protection against atmospheric influences and for continuous insulation an element for removing vaporous moisture that enters the insulation under the influence of heat and mass transfer forces. Therefore, it is of particular importance optimal selection: insulation - protective and finishing layer.
The choice of protective and finishing layers is determined primarily by economic opportunities. Facade insulation with a ventilated air gap is 2-3 times more expensive than solid insulation, which is no longer determined by energy efficiency, since the insulation layer is the same in both options, but by the cost of the protective and finishing layer. At the same time, in the total cost of the insulation system, the price of the insulation itself can be (especially for the above incorrect options for using cheap non-plate materials) only 5-10%. Considering the facade insulation, one cannot help but dwell on the insulation of the premises from the inside. Such is the property of our people that in all practical undertakings, regardless of objective laws, they are looking for extraordinary ways, be it social revolutions or the construction and reconstruction of buildings. Internal insulation attracts everyone with its cheapness - the cost is only for a heater, and its choice is quite wide, since there is no need for strict compliance with reliability criteria, therefore, the cost of a heater will no longer be high with the same thermal insulation performance, the finish is minimal - any sheet material and wallpaper labor costs are minimal. The usable volume of the premises is reduced - these are trifles compared to the constant thermal discomfort. These arguments would be good if such a decision did not contradict the laws of formation of the normal heat and moisture regime of structures. And this mode can be called normal only if there is no accumulation of moisture in it during the cold season (the duration of which for Kyiv is 181 days - exactly half a year). If this condition is not met, that is, when the vaporous moisture condenses, which enters the outer structure under the action of heat and mass transfer forces, the materials of the structure and, above all, the heat-insulating layer become wet in the thickness of the structure, the thermal conductivity of which increases, which causes even greater intensity further condensation of vaporous moisture. The result is a loss of thermal insulation properties, the formation of mold, fungi and other troubles.
Graphs 1, 2 show the characteristics of the heat and moisture conditions of the walls during their internal insulation. A claydite-concrete wall is considered as the main wall, and foam concrete and PSB-S are the most commonly used as heat-insulating layers. For both options, there is an intersection of the lines of partial pressure of water vapor e and saturated water vapor E, which indicates the possibility of vapor condensation already in the intersection zone, which is located at the boundary between the insulation and the wall. What this decision leads to in buildings already in operation, where the walls were in an unsatisfactory heat and moisture regime (photo 3) and where they tried to improve this regime with a similar solution, can be seen in photo 4. A completely different picture is observed when the terms are changed, that is, the placement of a layer of insulation on front side of the wall (graph 3).
Chart #1
Chart #2
Chart #3
It should be noted that PSB-S is a material with a closed-cell structure and a low vapor permeability coefficient. However, for this type of materials, as well as when using mineral wool boards (Figure 4), the mechanism of thermal moisture transfer created during insulation ensures the normal moisture state of the insulated wall. Thus, if it is necessary to choose internal insulation, and this may be for buildings with an architectural value of the facade, it is necessary to carefully optimize the composition of thermal insulation in order to avoid or at least minimize the consequences of the regime.
Chart No. 4
Walls of buildings of well brickwork
The heat-insulating properties of the walls are determined by the layer of insulation, the requirements for which are mainly determined by its heat-insulating characteristics. The strength properties of the insulation, its resistance to atmospheric influences for this type of structures do not play a decisive role. Therefore, PSB-S slabs with a density of 15-30 kg / m3, mineral wool can be used as a heater soft slabs and mats. When designing walls of such a structure, it is necessary to calculate the reduced resistance to heat transfer, taking into account the effect of solid brick lintels on the integral heat flux through the walls.
Walls of buildings of a frame-monolithic scheme.
A characteristic feature of these walls is the possibility of providing a relatively uniform temperature field over a sufficiently large area of the inner surface of the outer walls. At the same time, the supporting columns of the frame are massive heat-conducting inclusions, which necessitates mandatory verification of compliance of temperature fields with regulatory requirements. The most common as the outer layer of the walls of this scheme is the use of brickwork in a quarter of a brick, 0.5 bricks or one brick. At the same time, high-quality imported or domestic bricks are used, which gives the buildings an attractive architectural appearance (photo 5).
From the point of view of the formation of a normal humidity regime, the most optimal is the use of an outer layer of a quarter of a brick, but this requires high quality of both the brick itself and the masonry work. Unfortunately, in domestic practice, for multi-storey buildings, reliable masonry even of 0.5 bricks cannot always be ensured, and therefore the outer layer of one brick is mainly used. Such a decision already requires a thorough analysis of the thermal and moisture regime of structures, only after which it is possible to make a conclusion about the viability of a particular wall. Foam concrete is widely used as a heater in Ukraine. The presence of a ventilated air layer allows you to remove moisture from the insulation layer, which guarantees the normal heat and moisture conditions of the wall structure. The disadvantages of this solution include the fact that in terms of thermal insulation, the outer layer of one brick does not work at all, the outer cold air directly washes the foam concrete insulation, which necessitates high requirements for its frost resistance. Taking into account the fact that foam concrete with a density of 400 kg/m3 should be used for thermal insulation, and in the practice of domestic production there is often a violation of technology, and the foam concrete used in such design solutions has an actual density higher than specified (up to 600 kg/m3), this design solution requires careful control during the installation of walls and upon acceptance of the building. Currently developed and in
stages of pre-factory readiness (a production line is being built) promising heat and sound insulation and, at the same time, Decoration Materials, which can be used in the construction of the walls of buildings of a frame-monolithic scheme. Such materials include slabs and blocks based on the Siolit ceramic mineral material. A very interesting solution for the construction of external walls is translucent insulation. At the same time, such a heat and moisture regime is formed in which there is no condensation of vapors in the thickness of the insulation, and translucent insulation is not only thermal insulation, but also a source of heat in the cold season.
