Multi-criteria thermal evaluation of wall enclosures of high-rise buildings insulated products based on modified fibers

In article results of research of versions of offered types of heaters on the basis of products from the modified fibers for designing energy efficient building enclosures residential high-rise buildings are presented. Traditional building materials (reinforced concrete, brick, wood) are not able to provide the required value of thermal resistance in areas with a temperate and harsh Russia climate in a single-layered enclosing structure. It can be achieved in a multi-layered enclosing structure, where the decisive role is played by new insulating materials with high thermal properties. In general, modern design solutions for external walls are based on the use of new effective thermal insulation materials with the use of the latest technology. The relevance of the proposed topic is to research thermoinsulation properties of new mineral heaters. Theoretical researches of offered heaters from mineral wool on slime-colloidal binder, bentocolloid and microdispersed binders are carried out. In addition, theoretical studies were carried out with several types of facade systems. Comprehensive studies were conducted on the resistance to heat transfer, resistance to vapor permeation and air permeability. According to the received data, recommendations on the use of insulation types depending on the number of storeys of buildings are proposed.


Introduction
External walls for energy-efficient buildings are designed by multilayer in accordance with [1] with the use of effective thermal insulation materials. With the advent of new materials and systems of enclosing structures, great attention should be paid to understanding the physical processes occurring in the external walls, for their competent design and construction [2][3][4].
In addition to calculating the resistance to heat transfer, it is necessary to calculate the moisture state. Resistance to heat transfer, determined at the surface of the wall, is significantly different from the reduced resistance to heat transfer of the outer wall due to the presence and influence of window slopes, exterior corners of walls, partitions, ceilings, heat-conducting inclusions [5][6][7].
The loss of condensate in multilayered enclosing structures leads to an increase in the humidity of building and thermal insulation materials and to a deterioration in their heatshielding properties. There is a need for calculating the moisture regime of building structures [8,9], since for an annual period of building operation there is accumulation of moisture inside the enclosing structure.
For a long time, the authors carried out theoretical studies of facade systems of multilayered wall fences [10][11][12][13], experimental studies [14][15][16] with various types of known insulants. The proposed work is devoted to the study of facade systems with insulation on new types of binders [17][18][19].

Materials and Methods
Theoretical studies were carried out with three options for the proposed insulation: a) mineral wool on slime-colloidal binder; b) mineral wool on bentocolloid binder; с) mineral wool on microdispersed binder.
Depending on the location of the heater in the enclosure used two options for insulation: • insulation -inside the enclosing structure; • insulation -outside the enclosing structure.
Advantages of the building technology of facade systems with air gap over singlewalled walls have been known for a long time: air circulation and thermal radiation in the air gap provides a rapid removal of moisture from the interior of the building, supporting walls, insulation.
The multi-storey residential building in Samara has been calculate. The exterior wall constructions for theoretical substantiation have been checked in three versions, with an experimental insulation in three variants. Schemes of wall constructions and options for insulation are presented in Table 1.  The outside insulation with cement-particle board.

Cementparticle board 2. Insulation 3.Reinforced concrete
The technique of thermal calculation was based on the requirements [1] using the graphical method and the method of dimensionless characteristics for humidity areas. The method of calculation humidity conditions of external walls according to the method of dimensionless characteristics includes the determination of vapour pressure in the typical design cross sections for the annual cycle. If the vapor pressure exceeds the maximum elasticity of steam, in this section, the formation of condensate.
The basis of the constructive solutions of the exterior walls in determining the given resistance to heat transfer of the main fragments of the railings take the thickness of the insulation calculated in accordance with [1]. In case of insufficiency of insulation, thickness of insulation layer increases, or considering or considering the possibility of inclusion in the project energy saving measures (insulation of nodes).
The results of calculation of constructive schemes of walls 1-3 with options of insulation for residential buildings in Samara are presented in table 2. Calculations of temperature fields were carried out according to the design schemes 1-3 in the thickness of the external walls using the specialized program THERM 5.2. The results are shown in Figures 1, 2 and Table 3.
The necessity of calculation for the accumulation and condensation of moisture in building enclosures were improved.
The outer joints of the walls to the three options of heaters 1c), 2a), 3a) was chosen for thermal estimates of temperature change over the cross section of the walls.
The junction of walls, insulated on the outside (Fig.2 1a, 1b) with facing of the CPB does not pass on the resistance to heat transfer (R0=2,333 (m 2 • 0 C)/W which is ≤ R req ), but passes the sanitary and hygienic conditions (Δt f =3,8 0 C ≤ Δt n = 4 0 C, as tint = 17,2 0 С > td = 16,2 0 C). The insulation of the joint is required. Fig. 2. Temperature fields along the cross-section of the outer joint of the walls: a -temperature isotherms according to scheme 3a); b -temperature distribution according to scheme 3a); Resistance to air permeability of building envelopes and structures Rinf des should not be less than specified resistance to air permeability Rinf req , m 2 •h•Pa/kg, determined by the formula (1): where ΔP -pressure difference of the air at the exterior and interior surfaces of building envelopes, Pa; Gn -normalized air permeability of building envelopes, kg/(m 2 •h).
The pressure difference of the air on the outer and inner surfaces of enclosing structures, the Pa, to the windward side were determined according to [1], Gn the normalized air permeability, kg/(m 2 •h), at the table 9 [20]. Breathability Gn, kg/(m2•h), the exterior walls must be not more than 0,5.
Was determined pressure difference of the air on the outer and inner surfaces of walling on the ground floor of the building with the height of buildings 20, 40, 60, 100 m, and the normalized resistance to air permeability Rinf req . According to the calculations on the water vapor permeability of scheme 3 based on resistance to air permeability of structures is not necessary. In the walls according to schemes 1 and 2, there are layers of plaster, which have a sufficiently high value of the resistance to air permeability.
The results of the structural analysis of walls with an experimental insulation on air permeability is presented in table 4.

Discussion
1. Heat and humidity calculations showed that the investigated insulation can be applied in the system with an outer insulated layer and using them in construction with brick facing, along with basalt wool ROCKWOOL or polyester staple fiber URSA. All of the investigated insulation are noncombustible and environmentally friendly, which is one of the important factors in the structural design of the wall. 2. The design of the system with external insulation and thin plaster layer is achieved by the high thermal uniformity of the insulated exterior walls. The durability of the facade before the first overhaul is about 25 years. The comparison of the three schemes of wall constructions the wall construction with external insulation has more advantages for all types of characteristics. Dew point is shifted to the outer wall surface that prevents the accumulation of moisture in the thickness of the structure. Other advantages of this system is the lack of a vapor barrier, the possibility of realization of various architectural solutions, high maintainability.
3. Calculations on the resistance to vapor deposition and air permeability of the enclosing structures of residential buildings with insulation based on modified fibers (three schemes of wall constructions) have been shown:  experimental insulation can be used in walls of residential buildings frameless construction system with insulation on the outside and frame system with brick facing, as they satisfy all heating requirements: resistance to heat, water vapor and lack of moisture in the enclosing structures of buildings;  according to the resistance to air permeability, the proposed heaters are recommended for high-rise buildings. More effective from experimental insulants based on mineral fibers -using a microdispersed modifier, which can be used in buildings up to 40 storeys;  in the construction of walls with facing brick and a thickness of the structural layer of 51 cm there is an increase of 1 cm in thickness of the proposed insulation -mineral wool