Ohio State University in Columbus has installed a 12,000-square-foot green roof on Howlett Hall, which is home to the Department of Horticulture & Crop Sciences and the Food Science Processing Plant. The green roof replaces a tar and chip roof that was hot and unattractive, the university says. The roofwill prevent 191,196 gallons of polluted water from entering the Olentangy River each year.