Effect of Moisture on Hygrothermal and Energy Performance of a Building with Cellular Concrete Walls in Climatic Conditions of Poland.

The European building industry has for years utilized autoclaved aerated concrete (AAC), especially in Germany and Poland. However, AAC shows considerable decrease of thermal resistance with increasing moisture content. The main objective of this paper is to quantify the effect of initial moisture on the hygrothermal and energy performance of AAC used in a residential house located in Warsaw, Poland. Annual profiles of moisture content in a 36.5 cm cellular concrete wall were derived for Polish climatic conditions using a state-of-art model of coupled heat, air, and moisture transfer in porous building materials. Possible variations of the hygrothermal performance and differences in kinetics of drying of the wall exposed to the typical and real weather conditions for a specific year were estimated. Moisture distribution changes in the ACC wall were also calculated for three years of exposure in Poland's typical climatic conditions. Space- and time-averaged values of moisture content, thermal conductivity, apparent density, and specific heat of cellular concrete layer were calculated for each month of the analyzed period. These averaged material properties were used in DOE-2.1E simulations of the whole building energy performance of a 286 m2 (3,079 ft2) residential house for each month of the analyzed period. Moreover, monthly values of energy released or absorbed on the internal surface of the wall, due to the condensation or evaporation of moisture, were calculated and used to approximate the total effect of initial moisture drying on energy performance of the whole building. [ABSTRACT FROM AUTHOR]