Influences of the Indoor Environment on Heat, Air and Moisture Conditions in The Building Component: Boundary Conditions Modeling

Current models to predict heat, air and moisture (HAM) conditions in building components assume uniform boundary conditions, both for the temperature and relative humidity of the air in an indoor space as well as for the surface transfer coefficients. Such models cannot accurately predict the HAM conditions in the component and on the surface of the component with non-uniform air temperature or relative humidity distributions in an indoor space. Moreover, the heat and moisture surface transfer coefficients strongly depend on the local air velocity, local temperature, water-material interactions and water content at the material surface and surface texture of the material. The objective of the present paper is to analyze the influence of the non-uniform local air velocity near the surface of a building component on the HAM conditions in the component. A case study and sensitivity study have been used to investigate this influence. The research showed that the indoor environmental conditions and local airflow velocity have a relatively large influence on the predicted HAM conditions in a building component. The influence of the convective surface heat transfer coefficient on the HAM performance of the component is relatively large compared to the influence of the convective surface mass transfer coefficient. With respect to the analyzed building component, the investigations showed that assuming an average value for the surface mass transfer coefficient is acceptable, while assuming an average value is not acceptable for the convective surface heat transfer coefficient. The study showed that the influence on the surface relative humidity is limited.