Construction solutions for the exterior walls in the process of increasing the width of residential buildings of brownfield construction in seismic hazardousand dry hot conditions of Central Asia

• Main Author: Usmonov Shukhrat Zaurovich
• Format: Article
• Language: English
• Published: Moscow State University of Civil Engineering (MGSU) 2014-02-01
• Series: Vestnik MGSU
• Subjects: exterior wall; brownfield construction; framework; wide-block buildings; ventilated air space; insulated screen; thermal insulation of residential buildings; Central Asia; Tajikistan; seismic hazard; hot-arid climate; construction solutions; reconstruction
• Online Access: http://vestnikmgsu.ru/files/archive/issues/2014/2/ru/7.pdf

The main object of this study is the reconstruction, renovation and modernization of the housing built in the period 1975—1985. These buildings have low energy efficiency due to the poor thermal insulation properties of the walls. These apartments do not meet the necessary requirements for year round warmth and comfort.Reconstruction is more preferable, than new-build, because of the cost saving for the land acquisition. Reconstruction is generally 1.5 times cheaper than new-build with 25—40 % reduced cost on building materials and engineering infrastructure.Increasing the width of the apartment blocks from 12 to 15 m can save 9—10 % on the consumption of thermal energy for heating and reduce the m2 construction cost by 5.5—7.0 %. In—5-9 storey high-rise buildings the savings are 3—5 %.Therefore, the width of the apartment block should preferably be between 9—12 m but could be extended to 18 m. The depth of the apartments themselves will be 5.4 — 6.0 —7.2 or 9.0 m. During the reconstruction of 5-storey residential buildings (Building Type105) in a seismic zone, an increase in the width of the block and the lateral stiffness of the building is achieved by building a new reinforced concrete (RC) frame on both sides of the building with a depth of between 2 and 6 m. This technique is especially effective in increasing the seismic resistance of the building. Self-supporting walls of cellular concrete blocks (density 600 kg/m3 and a thickness of 300 mm) are constructed on the outside of the frame, taking care to avoid cold bridges.Model studies have shown that in the conditions of hot-arid climate the thickness of the air gap in a ventilated facade does not significantly change the cooling-energy consumption of the building, and heating consumption is significantly increased. The building's energy consumption is most influenced by the volume of the air in the air gap. By increasing the ventilation rate in the air gap, the energy consumption for building heating increases and for cooling — slightly decreases. For the conditions of the northern region of Tajikistan, the recommended optimal thickness of the air gap with ventilation is 60 mm.