Assessment of the Energy-Efficient Modernization of Residential Historical Buildings in Kiev

Most of residential historical buildings in Kyiv, Ukraine are in need of energy efficiency modernization. The present research exposes the assessment of warming effectiveness for the certain enclosing structures in historical residential buildings, considering the overall thermal balance of building. Heat losses through certain enclosing structures considering actual thermal resistance were estimated, also in compliance with standard requirements for thermal resistance of enclosing structures according to the standard DBN В.2.6-31:2006. It turned out that the warming of the whole building envelope and the replacement of transparent enclosing structures allows to reduce the heat flux of the heating system for compensation of thermal losses through the building envelope in 3 times.

In this article the possibility of energy-efficient modernization of residential historical buildings in Kiev was considered in accordance with modern standards [10].
Residential building built in 1909 on the Malaya Zhitomirskaya street, 12-A, Kiev was taken as an example for the assessment (historical and architectural monument of local importance [2]. It should be noticed that the design of walling (external walls, attic slabs and basement ceiling) in residential historical buildings of St. Petersburg and Kiev have the common features [2][3][4][5][6][7][11][12][13].
For example, exterior walls have a variable thickness and become thinner with height: the wall thickness varies in the range from 2 to 5 bricks. Therefore, the methodology of energy efficiency modernization can be quite similar for such buildings.

Thermo-technical calculation of building envelope
Design conditions for Kiev and numerical values used for further calculations presented in Tables 1, 2  The facade and section of the building on Malaya Zhitomirskaya st., 12A is illustrated in Figure 1. The results of calculation for the bricks wall thickness presented Table. 3. Dependence diagram of heat transfer performance uniformity factor to the thickness of brick wall presented Figure 2. The calculation results of design and standard values of structural thermal resistance for a residential building are shown in Table 4. Notes: 1. The actual thermal resistance for the exterior walls which is specified in the denominator was determined taking into account the coefficient of thermotechnical homogeneity (r -heat transfer performance uniformity factor); 2. The values of thermal resistance for the overlap above the unheated basement were specified in the denominator with coefficient n=0.4, which was taken for the overlap above the unheated basement below the level.
3. The minimum required thermal resistance for the sanitary and hygiene standards was defined by the standard temperature differential between the inside air temperature and temperature of the inner surface of the building envelope [1]; 4. Specified indicators were adopted for the 1 st temperature zone of Ukraine [1].

Heat losses calculation. Variant 1
Considering the first type according to actual terms of thermal resistance of enclosing structure (Table 5).

Heat losses calculation. Variant 3
We consider the option of insulating external walls only (Table 8) Table 8. Thermal resistance of enclosing structure.

Heat losses calculation. Variant 4
We consider the option of replacing old windows with the glass units (Table 9)

Heat losses calculation. Variant 5
We consider the option of warming the attic slabs only (Table 10) We consider the option of warming the basement ceilings only (Table 11) General and additional heat losses through the building envelope at the design outdoor temperature minus 22°C are as follows: -considering actual terms of thermal resistance -103910 W; -considering the observance of regulatory requirements [10] for whole walling -33950 W; -considering the observance of regulatory requirements only for external walls -60030 W; -considering the observance of regulatory requirements only for transparent structures -93650 Вт; -considering the observance of regulatory requirements only for the attic slabs -90550 Вт; -considering the observance of regulatory requirements only for the basement ceiling -100640 Вт.

Conclusion
Thus, implementation of energy saving measures such as insulating for whole walling and replacing transparent walling allows to reduce heat flux of the heating system which compensates the heat loss through the building envelope in 3.1 times. At the same time the external walls facing Malaya Zhitomirskaya st. have to be insulated from the inside, and in other cases the external warming is possible.