The quality and quantity of air in the spaces we inhabit has a direct impact on our health, wellbeing, and cognitive function. The impacts can vary widely, depending on multiple factors including the quality of indoor air and the concentration of contaminants; the rate of intake, or quantity of outside air supplied; and the length of exposure to the air, or the amount of time spent indoors. We spend more than 90 percent of our time indoors, which considerably lengthens our time of exposure to indoor air. This heightens the importance for us as designers and engineers to ensure that the indoor environment is designed to reduce contaminates and improve the quality of air, and increase the amount of outside air supplied compared to most standards. It is also key to ensure that we are doing this while reducing energy consumption, without adding to the outdoor pollutants or emissions, which are a leading cause for the deterioration in the quality of our outdoor air.
From a combination of primary research studies, we’ve noted recurring outcomes that indicate a reduction of volatile organic chemicals (VOCs), lower CO2 differentials between indoor and outdoor air, and mechanical systems that double the ASHRAE Standard 62.1-required outside air rates are all indicators of improved IAQ. These factors also tend to have positive effects on human health and performance.
What Does the Research Tell Us?
There are a number of studies that show us the magnitude of IAQ on human health.
Blackline in Woodland Hills, California by DLR Group. Photo by Andrew Scott.
In 2004, Myatt et al studied three office buildings in Boston with varying indoor CO2 differentials, or indoor minus outdoor CO2.1 The study found a 6.8 percent reduction in risk of exposure to airborne-transmitted rhinovirus, or colds, for workers in offices with an indoor CO2 differential of less than 100 ppm (parts per million) compared to those in offices with indoor CO2differential higher than 100 ppm. The study even found that rhinoviruses can recirculate through systems with low outdoor air supply, increasing the risk of some airborne illnesses. An increased risk for upper respiratory tract infections can mean employees take sick days or come to work while sick – which wreaks havoc for both colleagues and productivity.
In 2000, a study by Milton, Glencross, and Walters tracked 3,720 hourly employees across forty buildings at Polaroid in work areas with varying rates of outdoor air ventilation.2 The study found a 35 percent reduction in short-term sick leave for employees in work areas with an outdoor air supply rate of 24 liters per second, (L/s), or 50 cubic feet per minute (CFM) per person, compared to employees in work areas with an outdoor air supply rate of 12 L/s or 25 CFM per person. The reduction in short-term sick leave resulted in 1.2-to-1.9 fewer days of sick leave per person, per year.