The South Coast Air Basin of California, a region of 16.8 million people, is among the most polluted air basins in the United States. A multidecadal effort to attain federal air-quality standards has led to significant progress, but much more work remains. Are recently implemented statewide building efficiency standards on rooftops counterproductive to these goals? With comprehensive regional models and intensive development of model input parameters, our research has identified the air-quality consequences that are expected to result from these efficiency standards. The results can inform policies to mitigate some air-quality penalties, while preserving the benefits of building efficiency standards. This work also sheds light on potential future policies aimed at reducing urban heating from pavement surfaces.