Impact of humidity on formaldehyde and moisture buffering capacity of porous building material

The aim of this article is to present a validated model to study the influence of humidity on formaldehyde sorption of building material and the effect of formaldehyde and moisture buffering capacity of hygroscopic porous material on indoor air environment. New empirical formulas proposed to describe the diffusion and partition coefficients as functions of humidity based on previous experimental data are incorporated in a coupled moisture and pollutants transport simulation model. The numerical model that takes into account the effect of RH (or moisture) in building materials on VOC diffusion can be used to simulate VOC emissions/sorption from building materials. The developed model is implemented in the environment SPARK (Simulation Problem Analysis and Research Kernel) using finite difference technique. The model is then applied to study the hygric and formaldehyde (FOR, a water soluble VOC) behavior of calcium silicate (CS) subjected to different dynamic conditions of RH and formaldehyde. The results obtained in this paper help to emphasize the importance of moisture and formaldehyde buffering capacity as a new key parameter when selecting clean and hygroscopic building materials in building design because they can contribute to dampen indoor RH and formaldehyde variations. In addition, the impact of RH variation is significant and needed to be taken into account in the simulation to correctly predict the indoor formaldehyde concentration. The model developed in this paper can also be used to optimize the hygric performance and IAQ in building.