The hygrothermal behavior of an external, 8 in. cellular concrete wall was numerically simulated for the first three years of building use. A state-of-the art model of coupled heat, air, and moisture transfer in deforming porous building materials, HMTRA-DEF, was used for the simulation. Climatic data for a typical meteorological year for Sacramento, California, and Miami, Florida, were applied for the definition of external boundary conditions. Four different cases for finish layers--interior and exterior wall surfaces, with and without a vapor-retardant paint--were considered. Based on the simulation results, space and time- averaged values of moisture content, thermal conductivity, apparent density, and specific heat of the cellular concrete layer were calculated for each month. These averaged material properties were used for a DOE-2.1E simulation of the wholebuilding energy performance of a 143.1 m² (1540 ft²) residential house for each month of the analyzed period. Additionally, monthly values were calculated for energy released or absorbed on the internal surface of the wall as a result of the condensation or evaporation process. These results have been used to approximate, for various types of finish layers on the external walls, the effect of technological moisture drying on the energy performance of the whole building during the first few years of its use. The results of the analysis are presented and discussed.

Authors: Dariusz J. Gawin, D.Sc.; Jan Kosny, Ph.D.
Citation: Thermal Performance of the Exterior Envelopes of Buildings VIII
Keywords: December, Florida, 2001