A new way of cleaning city air

Posted by Susan DeFreitas, EarthTechling

Unbeknownst to many, buildings can actually produce polluted exhaust, not unlike cars.

That’s because all those lovely things that can conspire to pollute our indoor air – carbon dioxide, smoke, mold, and dust, as well as formaldehyde and other Volatile Organic Compounds (VOCs) off-gassed by building materials and furnishings, cleaning agents and copy machines — can become concentrated in the air released by building HVAC systems into the general atmosphere.

What’s worse, in your average urban wind-tunnel or “canyon” (formed by tall buildings in close proximity to one another), the exhaust stream of one building can actually be sucked up by the HVAC system of another in its well-meaning attempt to cycle fresh air in.

This according to to Ted Stathopoulos and Bodhisatta Hajra — researchers at Concordia University in Portland, Ore. – who performed a study on this effect in Concordia’s cutting-edge wind tunnel laboratory, a huge underground research facility that allows engineers to test the atmospheric dispersion of pollution and toxins in any given setting.

After examining the trajectory and amount of air pollution from a building to its neighbors downwind, they concluded that the industry standards developed decades ago by the American Society of Heating, Refrigerating and Air-Conditioning Engineers need some significant updating.

Toward that end, they have developed a set of environmentally friendly building guidelines for cities designed to supplement those existing rules.

According to their findings, the process by which air pollution spreads from one building’s exhaust stack to another’s intake is affected by the height and spacing between buildings. Logically enough, their guidelines call for the intake vents on buildings downwind of a polluter to be placed upwind of that building’s stack, and closer to its more sheltered wall.

They also recommend that air intakes should not be placed on rooftop locations downwind of a low stack and the protected wall of the emitting building. Lastly, they recommend increasing the spacing between buildings to reduce the possibility that pollutants from one will be re-ingested by another.

Their study and its findings were recently published in the peer-reviewed journal, Building and Environment.

Susan DeFreitas, EarthTechling