CLEARING THE AIR

We all want homes that are comfortable and energy efficient. But all our efforts to replace drafty windows, seal up air leaks, and blanket wall cavities with insulation have had an unfortunate consequence: They’ve made the air in our houses less healthy to breathe. More of the airborne pollutants that once might have found their way outside—household chemicals, smoke, pet dander, and cooking gases, to name a few—are building up inside. Our well-intentioned efforts to restrict the flow of air in and out of our houses have led to indoor air-pollution levels that can be two to five times higher than those outside, according to the Environmental Protection Agency.

That doesn’t mean we should give up on making our houses tighter, of course. But it does mean now is a good time to pay as much attention to indoor air quality, or IAQ, as we do to energy efficiency. That begins by getting a better understanding of how to balance the movement of air in and out of a house, and of mechanical systems that usher