NUMERICAL SIMULATION OF PARTICLE PENETRATION THROUGH THE BUILDING ENVELOPE

Outdoor particles can penetrate into indoor environment through unplanned airflow paths, which can be a significant source of indoor particles, especially when there is no mechanical ventilation system and doors and windows are closed in a residential building. Fiberglass insulation is commonly used as the insulation material in wall cavities in residential buildings for energy saving purpose. A significant fraction of infiltrating air has been found in real buildings to pass through the wall systems with leakage paths. In this study, a simplified two-dimensional CFD model was set up to simulate particle penetration through a mid-scale wall system of typical wood-framed residential houses in North America, assuming crack heights of I mm (in the vertical direction) and 3 mm (in the horizontal direction) and with fiberglass insulation width of 0.14 m. The transport process of 0.001-10 pm particles in the cracks were simulated by Eulerian - Eulerian method, while particle transport in the fiberglass was accounted by an additional sink term in the governing equation, derived from the classical filtration theory. Results showed that 0.05 um - 1 mu m particles were the most penetrable particles, though fiberglass insulation media greatly reduced particle penetration by more than 90%. It was also found that when there were short horizontal flow paths and long vertical flow paths, particle penetration factors were much larger except for small particles less than 0.05 um where Brownian diffusion played an important role for particle deposition for this size range.