Effect of Uncertainty in the Hygrothermal Properties on Hygrothermal Modeling

Building envelopes are subject to the transient climate conditions. Moisture transfer which is coupled with heat transfer is an important issue in the field of building science. The moisture transfer and accumulation within building envelopes can lead to poor thermal performance, metal corrosion, wood decay, structure deterioration, microbial and mold growth. It is of great significance to investigate the hygrothermal behavior of building envelopes to improve the building energy efficiency, service life of buildings and indoor comfort. Though a lot of works have been done on the hygrothermal behavior of building materials, the experimental investigation is relatively lack. The hygrothermal properties of commonly used building materials which are the foundation of hygrothermal modeling often show a great uncertainty in the existing literatures. It may lead to significant discrepancy in the numerical results. In this paper, the local sensitivity analysis (LSA) method is used to investigate the effect of the uncertainty in hygrothermal properties, including the thermal conductivity, sorption isotherm, water vapor permeability and liquid water permeability, on the hygrothermal modeling. The results show that the uncertainty in the sorption isothermal and vapor permeability can lead to pretty high discrepancy in the distribution of the moisture content. The uncertainty in the sorption isothermal and vapor permeability causes relatively high error in temperature. These two properties must be determined accurately. The error caused by the uncertainty in liquid water permeability is limited since the relative humidity of the outdoor atmosphere is usually lower than 95% under which the capillary conduction is extremely weak.