New research from the Harvard School of Public Health finds that workers in high-performing, green-certified buildings think and sleep better than those in similar buildings that were not green-certified.

Led by Dr. Joe Allen, director of Harvard’s Healthy Buildings program, researchers studied 109 workers in 10 buildings in various climate zones across the country for one week. All the buildings were high-performance in terms of having high ventilation rates and low total volatile organic compounds (VOCs), but six were specifically green-certified.

The researchers found that compared to workers in the non-certified buildings, workers in the green-certified buildings had 26 percent higher cognitive function scores, reported 30 percent fewer “sick building” health symptoms, and saw 6.4 percent higher “sleep quality scores” (as measured by wearable sleep monitors).

This research follows a bombshell 2015 study by the same group that found elevated indoor carbon dioxide (CO2) has a direct and negative impact on human cognition and decision-making — at CO2 levels that most Americans (and their children) are routinely exposed to today inside classrooms, offices, homes, planes, and cars.

That first study measured a typical participant’s cognitive scores dropping 21 percent with a 400 ppm increase in CO2:

In the new study, the biggest differences in cognitive function between workers and the two types of buildings were in crisis response (73 percent higher in green-certified buildings); “applied activity level — the ability to gear decision-making toward overall goals (44 percent); focused activity level — the capacity to pay attention to situations at hand (38 percent); and strategy (31 percent).”

In both studies, researchers made use of a sophisticated multi-variable assessment of human cognition used by a State University of New York (SUNY) Upstate Medical University team, led by Dr. Usha Satish.

In an interview with Climate Progress, Dr. Allen explained the reasons why he thinks workers in the certified green buildings outperformed those in the high-performance buildings that weren’t certified.

First, workers in the certified buildings spent more time working in the “ideal comfort zone” (the optimum range of temperatures and humidities, which provide 90 percent or higher occupant satisfaction). Second, those workers had more and better quality light, most likely driven by more use of daylighting. Future studies will examine these factors in greater detail.

You may be wondering how it is that people in green-certified buildings slept measurably better at night. The answer appears to be better quality (bluer) light and more light (a larger contrast between daytime exposure and night-time):

CREDIT: Harvard University

The findings from this study were presented pre-publication at the U.S. Green Building Council’s annual Greenbuild conference. More information on both studies is available here.