A mathematical model for predicting the indoor moisture variation by using moisture buffering theory

Indoor air humidity evaluation plays an of great importance role on the thermal comfort and building energy consumption. The utilization of hygroscopic materials as building materials acts on the indoor air humidity by regulating its humidity fluctuations, and then reduces a certain fraction of energy consumption on the air conditioning systems. Based on the Fick’s law, the physical process inside these hygroscopic materials requires the determinations of hygrothermal properties, which signify the extensive and reiterative experiments. While in many building simulation toolboxes, moisture buffering behavior has been evaluated by either simple approximations or complicated heat and mass model. In this case, we developed a mathematical model about the moisture transport with acceptable solution time and accuracy in terms of the moisture buffer value (MBV) theory. Considering that MBV originally represents the moisture buffering capacity of those hygroscopic materials, we did some mathematical deduction about MBVs under different boundary conditions. Then the definition of time-average MBV has been used, and all the required parameters was obtained from the practical MBV test. By comparing the new moisture buffer value model (MBM) with HAMT model, the results indicated that MBM could provide reasonably accurate prediction for indoor moisture variation.