Designed thermophysical parameters of walls made of autoclaved aerated concrete blocks

The object of investigation are apartment residential buildings located in various climatic zones of the Russian Federation with application of outer walls made of autoclaved aerated concrete blocks (AAC). Based on the results of thermophysical calculation it is established that application of heat conductivity of AAC according to Russian standard (GOST 31359–2007) significantly overestimates the design total resistance to a heat transfer (R-value) of walls made of AAC and it is not recommended to use when developing the project documentation. Use of these data also overestimates a class of energy saving of buildings. Based on the results of thermophysical calculation it is shown that values of the reduced resistance to a heat transfer of the walls made of AAC conform to minimum admissible step-by-step requirements of the Russian standard (SP 50.13330.2012). Divergence of calculated and measured R-values is caused, mainly, by a discrepancy of designed thermophysical parameters of the material layers accepted depending on operated conditions of the building components. In comparison to the Russian standard (GOST 31359-2007) the calculated R-values based on the results of laboratory researches of heat conductivity of AAC provide the best approach to the measured values in design. Calculation in an assumption of linear dependence of heat conductivity on humidity underestimates temperature in the thickness of a building component. Application in thermophysical calculations of exponential dependence of
heat conductivity on humidity of AAC, according to the received results of pilot studies, allows estimating more precisely the thermal conditions of outer wall in a designing process of buildings.