Before he became a public health researcher at Harvard, Joseph Allen investigated hundreds of “sick buildings” as a consultant for owners who complained about illness in workers or residents from mold, dampness, and other unhealthy conditions.

Sometimes the fixes were easy—increase ventilation—and sometimes they were harder—poor construction—but over time, Allen began to realize that considerable money and pain could be saved if buildings were optimized for human health at the outset.

“People know that their physician plays an important role in their health, but sometimes building managers can play a nearly equal role,” says Allen. “The janitor of a school, for example, has a big impact on the health of those kids.”

That influence stems from a startling stat: Americans spend an