There’s been a lot of talk over the past 20 years about evidence-based design. EBD is the idea that improvements to the design of buildings, particularly to their interior spaces—more daylight, improved air quality, better lighting—can have a positive effect on human health and performance. The problem with EBD is that it’s very hard to conduct truly rigorous scientific studies on humans. Was it the improved lighting that enabled students to boost their test scores, or was it better airflow in the classroom? Did that hospital patient heal more quickly because she had a window with a view to the outside, or was she just a fast healer? Too many variables, not enough controls, so it’s anybody’s guess how much, if anything, the design contributed to the outcome.