BuildingAdvice has been analyzing buildings for well over a decade for Carbon Dioxide levels, Temperature, Relative Humidity, and Light among other variables. The results from each building and zone allows us to highlight Trends in the Built Environment like the persistent overventilation of buildings. In fact, according to our research, 77% of all zones in buildings across the United States and Canada are over-ventilated. Of the total population, only 5% are under ventilated, and a modest 18% are acceptable when compared to ASHRAE Standards, U.S. Green Building Council, Indoor Air Quality Association, Health Canada, BOMA, ENERGY STAR, and DOE. Carbon Dioxide levels measured during the occupied times that fall within 700-1000ppm on average are considered acceptable. Those below 700ppm are considered over-ventilated, and those above 1000ppm are considered under ventilated. While results included all building types, the highest concentration of building types experiencing under ventilation were K-12 buildings.