What to do in buildings when “fresh” air is actually polluted air?

Fresh air is great, right? Open up those windows, air out that stuffy room, take a deep breath of refreshing clean air. Ah, so healthy.

But “fresh” air isn’t always so fresh. In fact, in some locations it’s downright toxic. Yet the traditional approach to provide clean air inside buildings is to bring in outside air. For conventional buildings, this often means outside air seeping in through cracks in the building. For green buildings, this often means intentionally-designed “natural ventilation” strategies that passively flush interior air with exterior air. But for sites and cities where outdoor air is not fresh air, this strategy does not work.

Pittsburgh in the 1940s. (Image Courtesy of University of Pittsburgh)

I’ve got personal experience with this. For a couple years I worked in a building that met the most stringent green building requirements out there. To provide fresh air, the building monitored interior CO2 levels and automatically opened the windows when the air got too stuffy. This worked great for much of the building. But our office was at ground level facing a busy street with lots of diesel truck and bus traffic. The particulate matter borne by the “fresh” air coming in through those open windows was so high that it coated our desks in soot, not to mention our lungs. <Cough, cough!>

What otherwise would have been a fine “natural ventilation” approach to providing good indoor air failed because the “fresh” air was, in truth, toxic air.

You better believe that “natural ventilation” is not a popular strategy in polluted cities like Beijing.


Back in the 1940s, Pittsburgh’s air was at least as bad as Beijing’s is today. The infamous 1948 Donora smog incident was so intense that it killed 20 Pittsburghers and sickened 7,000 more over just a four-day period. This environmental disaster helped launch the modern clean air movement which led to great legislative and environmental progress. Happily, Pittsburgh’s air is much improved. Still, the city’s industrial legacy, soot from still-operating coal-fired power plants, and pollution from nearby fracking operations can still lead to pretty bad air in Pittsburgh, particularly by today’s standards.

The 1948 Donora smog incident. (Image Courtesy of California University of Pennsylvania)

So The Heinz Endowments has spearheaded the ROCIS Initiative in partnership with the University of Pittsburgh, Carnegie Mellon, the City, Allegheny County Public Health, and other agencies, including NK Architects and Thoughtful Balance. ROCIS (Reducing Outdoor Contaminants in Indoor Spaces) aims to “reduce the impact of exterior environmental pollution in southwestern Pennsylvania to improve healthy and energy efficient indoor environments where we live, work and learn.”

Tomorrow, at the International Passive House Conference in Vienna, NK’s Brandon Nicholson will present the initial findings of ROCIS and their implications for Passivhaus design and construction. According to ROCIS, one of the most effective ways to protect interior air from outdoor pollution is to combine an airtight building envelope with filtration of incoming air, two pillars of Passivhaus design.

Brandon will share data showing how the ROCIS mitigation measures that he employed in his historic Pittsburgh home, and the measures employed by our colleague Laura Nettleton in her home, dramatically improved interior air quality, even during spikes in outdoor air pollution.

The conclusions that Brandon draws from ROCIS are relevant far beyond Pittsburgh, of course. There’s a reason that Chinese designers and policymakers have grown so interested in Passivhaus design recently. It’s a building approach that promotes both human health and climate health.

Perhaps the air pollution and building design lessons from Pittsburgh will help Beijing clear its skies.

Read Brandon’s paper here