Consider, for example, the studies done by the Rocky Mountain Institute that justify the increased costs for daylight technology in the workplace through reduced employee absenteeism and increased productivity. This is an excellent example of good design improving the business bottom line. It is difficult to measure, but not impossible. Consider symptoms such as asthma, headaches, nausea, dizziness or fatigue. If you experience any of these at home and not elsewhere, it's cause to further investigate your personal living environment.
Smoke detectors are a common sight today.
No, not really. They are required in many cases because those companies that manufacture the devices lobbied for regulations. The same is true in the case of fire sprinklers, and probably numerous other products protecting our safety that are codified into the construction of our built environments. He did this because he thought it was the right thing to do. Similarly, The Center for Health Design thinks that encouraging the widespread development of life-enhancing environments is the right thing to do.