Modeling pollutant penetration across building envelopes

Journal Article · Sun Apr 01 04:00:00 EDT 2001 · Atmospheric Environment

DOI:https://doi.org/10.1016/S1352-2310(01)00218-7· OSTI ID:1009829

Liu, De-Ling; Nazaroff, William W

As air infiltrates through unintentional openings in building envelopes, pollutants may interact with adjacent surfaces. Such interactions can alter human exposure to air pollutants of outdoor origin. We present modeling explorations of the proportion of particles and reactive gases (e.g., ozone) that penetrate building envelopes as air enters through cracks and wall cavities. Calculations were performed for idealized rectangular cracks, assuming regular geometry, smooth inner crack surface and steady airflow. Particles of 0.1-1.0 {micro}m diameter are predicted to have the highest penetration efficiency, nearly unity for crack heights of 0.25 mm or larger, assuming a pressure difference of 4 Pa or greater and a flow path length of 3 cm or less. Supermicron and ultrafine particles are significantly removed by means of gravitational settling and Brownian diffusion, respectively. In addition to crack geometry, ozone penetration depends on its reactivity with crack surfaces, as parameterized by the reaction probability. For reaction probabilities less than {approx}10{sup -5}, penetration is complete for cracks heights greater than 1 mm. However, penetration through mm scale cracks is small if the reaction probability is {approx}10{sup -4} or greater. For wall cavities, fiberglass insulation is an efficient particle filter, but particles would penetrate efficiently through uninsulated wall cavities or through insulated cavities with significant airflow bypass. The ozone reaction probability on fiberglass fibers was measured to be 10{sup -7} for fibers previously exposed to high ozone levels and 6 x 10{sup -6} for unexposed fibers. Over this range, ozone penetration through fiberglass insulation would vary from >90% to {approx}10-40%. Thus, under many conditions penetration is high; however, there are realistic circumstances in which building envelopes can provide substantial pollutant removal. Not enough is yet known about the detailed nature of pollutant penetration leakage paths to reliably predict infiltration into real buildings.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Environmental Energy Technologies Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1009829
• Report Number(s): LBNL-47785
• Journal Information: Atmospheric Environment, Journal Name: Atmospheric Environment Journal Issue: 26 Vol. 35; ISSN 1352-2310
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
AIR
CAVITIES
DIFFUSION
EFFICIENCY
FIBERGLASS
FIBERS
GASES
GEOMETRY
OPENINGS
ORIGIN
OUTDOORS
OZONE
POLLUTANTS
PROBABILITY
REMOVAL
ROOFS
SIMULATION
WALLS
exposure infiltration ozone particles penetration factor reaction probability