Energy-tight buildings reduce our thinking capacity unless they’re properly ventilated, according to a Harvard University and Syracuse University double-blind study conducted recently. Who knew?

After spending decades making our buildings more energy efficient, it turns out that the CO2 and volatile organic compounds trapped in these “tight” buildings can make us dumb.

The Harvard School of Public Health study placed “knowledge worker” volunteers in spaces where researchers could control the different chemicals they breathed. Researchers increased and decreased CO2 and VOCs, one at a time, to understand their cognitive impacts.

The VOCs introduced to the study spaces are common to commercial buildings, coming from paints, carpet, particleboard, cleaning products and adhesives. During the study, some days had high CO2, some days had high VOCs, and other days, the “green building” days, had amounts more closely reflecting fresh, outdoor air.

The knowledge worker volunteers did their normal jobs in these spaces. At the end of each day, volunteers took cognitive performance tests, simulations that presented practical situations requiring practical solutions.

On the high CO2 days, volunteers’ cognitive performance was halved. With VOCs, the cognitive diminishment was even greater. On enhanced green days, when buildings were ventilated to approximate fresh air levels, crisis response scores went up 131 percent, strategic thinking scores went up 288 percent, and information usage scores went up 299 percent.

According to Joseph Allen, the lead researcher and Harvard faculty member on the study, “This is a big deal. The findings are strong, the magnitude of the effect is quite large, and we weren’t testing anything exotic.”

A follow-up study about to be published indicates that the cost benefit of ventilating buildings to fresh air levels is enormous. Researcher Allen said in a Living on Earth segment on National Public Radio that the per-employee cost of an energy-tight building is $30. The per-employee cognition improvement benefit of a “fresh air” building is $6,000.

United Technologies, a leader in the building technology industry, sponsored the first study. John Mandyck, UT’s chief sustainability officer, calls the study is a “game changer.”

“With optimized indoor environmental quality,” Mandyk said, “test scores over nine cognitive domains doubled. That really means better thinking in better buildings, and I think what’s most important here is that productivity often comes with a learning curve. In this case, all people have to do is breathe because the intelligence is in the air with readily achievable conditions that Harvard and its study partners found in this research.”

Study results have implications for Colorado’s Capitol, which has undergone renovation in recent years to restore its original beauty and make it energy-efficient. Coloradans will surely tolerate some leaking from the Capitol’s spacious 19th century windows if the fresh air keeps everyone in the building sharp as tacks.

Paula Noonan owns Colorado Capitol Watch, the state’s premier legislature tracking platform.