Development of a fast moisture prediction model based on the moisture buffer value theory

Moisture transfer in buildings significantly affects indoor thermal comfort, energy consumption, and durability of construction materials. It is crucial to predict the moisture storage and transfer in building simulations accurately. However, moisture transfer was neglected in many simulation tools for building performance analysis. In those calculation tools, including a moisture model, moisture transfer has been either estimated by simple approximations or calculated by complex combined heat, air, and moisture transfer (HAMT) models that require orders of magnitude more computing time than simple calculations. In this study, a new moisture prediction model with fast solution time and reasonable accuracy was developed based on the moisture buffer value (MBV) theory. The moisture buffer value was initially designed to quantify the moisture buffering ability of porous building materials. Very little research has been conducted to use MBV for calculating building energy performance directly. This paper first studied the MBVs under different boundary conditions (i.e., square wave and harmonic wave variation of vapour content), and then a time-average MBV was proposed. Experiments were carried out to get the parameters for the new FMBM model. Finally, simulation tests were conducted to compare the FMBM model with other moisture prediction models (e.g. EC, EMPD and HAMT models). The results indicate that the FMBM can provide a fast and reasonably accurate solution for indoor moisture prediction.