Breathe Easy: You Can Improve Indoor Air Quality by Design
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 CO2 differential 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.
Multiple controlled laboratory studies have identified significant differences in various performance measures when people are exposed to high concentrations of VOCs and/or CO2. Cognition, mathematics and memorization, and decision making were all negatively impacted by higher levels of these compounds. In some cases, these effects were seen below what is considered the acceptable threshold of 1000 ppm CO2.
Studies like one from Allen et al in 2012 have shown that “green” workspaces with higher outdoor ventilation rates can improve cognition and task performance by removing harmful compounds from the air. Participants completed office-type tasks during exposure to varying concentrations of airborne VOCs and carbon dioxide. The study tested three environments: high concentration of VOCs, or conventional; low concentration of VOCs, or green; and low concentration of both VOCs and CO2, green+, which are typical characteristics of a system with a high outdoor air ventilation rate. The study found that the green environment improved cognition by 61 percent, and the green+ environment by 101 percent.
Confidential Technology Client in Irvine, California by DLR Group. Photo by Marco Zecchin Enterprises.
In 2012, Satish et al asked participants to complete nine different performance tasks during exposure to varying levels of CO2.3 The highly predictive study found that a change in CO2 levels from 600 to 1000 ppm degraded raw scores for performance by 11-to-23percent– despite 1000 ppm widely being considered acceptable. At 2500 ppm, most measures of performance decreased into the “dysfunctional” range – up to 94% lower -- and in many ways mimicked the performance of an intoxicated person. In other words, as CO2 increased, all scores decreased – in particular strategic thinking and decision-making.
In 2002, Rowe studied 39 offices in the Wilkinson Building at the University of Sydney after mechanical air conditioning systems had been replaced with a mixed-mode system.4 The study found a 79 percent annual energy savings in HVAC use and an 18 percent increase in perceived productivity after the replacement. The perception of productivity was dependent on the qualitative impact reported by the users.
How Can Design Help?
Here are our top five design strategies to deliver healthy IAQ.
Sample HPD Label from Declare. Image courtesy of International Living Future Institute.
Reduce off-gassing with low-emitting materials and post-occupancy maintenance. Use product health product declarations (HPDs) to find solutions that minimize toxic ingredients and off-gassing. An HPD is a manufacturer document that discloses product ingredients and any associated health hazards. Certain building product certifications and labels, such as Declare, Cradle to Cradle, and Greenscreen vetting, can aid in simplifying material selections. This can include, but is not limited to, paints and coatings, interior adhesives and sealants, flooring, insulation, and furniture and furnishings. It is important to simultaneously ensure product durability and ease of maintenance without the use of toxic cleaning products. It is also important to maintain an operational standard that includes ongoing work with your design team to ensure new furniture brought in post-occupancy will not off-gas, and using cleaning products that do not include pollutants.
Nestle USA Harper Building in Solon, Ohio by DLR Group. Photo by Kevin G Reeves.
Source filtration, including air intake and building entrances. Ensure all entrances are provided with design solutions to minimize entry of contaminates, such as entry mats for source pollution control. Outside air intake locations for HVAC can be a key driver in limiting contaminates and unpleasant odors. Provide outdoor air intake away from sources of pollution, and smells from traffic, restaurants, and other distinguishable sources. Provide filtration like MERV 13 for outside air intake. An even higher level of filtration, such as MERV 15 and/or carbon gas filters, might be a good solution for locations where there are recurring issues with outside air quality from factories or fires. It is also important to factor in the impact of fan energy consumption with use of filters.
DLR Group ‘s Los Angeles studio. Photo by Andrew Scott.
Use innovative mechanical design tactics to increase outside air supply and/or specify control sequences that keep CO2 ppm below optimum levels while minimizing energy consumption. These tactics and solutions should include energy performance as part of the decision-making equation. Mechanical design that keeps energy consumption and CO2 emissions low while maximizing air quality is key to improving air quality both indoors and outdoors. Some options include decoupling outside air ventilation from heating and cooling systems; installing 100 percent outside air systems with zone cooling and heating, such as chilled beam systems or radiant systems; and displacement or under-floor air systems that increase ventilation effectiveness by supplying air closer to the occupants’ breathing zone. Dedicated outside air systems (DOAs) supply 100 percent fresh air required per the ASHRAE 62.1 standard or other local codes, with no mixing of return air. The sequence of controls for a CO2 differential between indoor and outdoor space should be less than 100 ppm, or have CO2 levels at 600 ppm or less when spaces are occupied. As part of the post occupancy plan, ensure a schedule is in place for the continuous cleaning and maintenance of the air filters.
Provide operable windows for cross ventilation, and allow users to control their environment in locations with good air quality. These operable windows should have electrical signals to switch off HVAC when windows are open. Strategic design of building form can enhance the use of operable windows, which is now considered an amenity.
Mall of America in Bloomington, Minnesota by DLR Group. Photo by Richard Brine.
Use select indoor plants to help filter indoor air and improve the quality of the circulated air. Design an interior landscape that can enhance biophilia, and selectively enhance air filtration. We recommend working with your facilities team to ensure a plant maintenance program is in place.
Air quality testing can be a final confirmation on whether the set air quality standards have been met. Testing can include periodic spot checks and measurements, or track ongoing measurements through air quality sensors. This tracking can help capture the impact of changes in the indoor environment that may be increasing contaminants in the space. Providing access to these metrics to the users can also help them track their environment and provide them with the confirmation of higher standards being met in their work place. DLR Group is currently conducting a firm-wide study that has turned our offices into labs that help our high-performance design teams evaluate and mediate any discrepancies detected in IAQ.
The reactions people have to indoor air contaminants vary widely and depend on multiple factors including the concentration of the contaminant, rate of intake, and length of exposure. In the U.S, the Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS) to establish exposure limits based on both duration and concentration for carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide. The WELL Building Standard expands on these requirements by incorporating standards from additional agencies, such as the World Health Organization (WHO), ASHRAE, and the U.S. Green Building Council's LEED, to set standards for air filtration and material selection that improves air quality. Both LEED and WELL standards include credits that advocate for improvements in indoor air quality through air filtration; low VOC materials; an increase in outside air quantity for ventilation; IAQ measurements; post occupancy maintenance of filtration; and cleaning protocols.
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- Myatt, T. A., Johnston, S. L., Zuo, Z., Wand, M., Kebadze, T., Rudnick, S., & Milton, D. K. (2004). Detection of airborne rhinovirus and its relation to outdoor air supply in office environments. American journal of respiratory and critical care medicine, 169(11), 1187-1190. Accessed at https://www.atsjournals.org/doi/pdf/10.1164/rccm.200306-760OC
- Milton, D. K., Glencross, P. M., & Walters, M. D. (2000). Risk of sick leave associated with outdoor air supply rate, humidification, and occupant complaints. Indoor air, 10(4), 212-221. Accessed at https://www.buildequinox.com/files/iaq/milton_vent_sick_rates.pdf
- Satish, U., Mendell, M. J., Shekhar, K., Hotchi, T., Sullivan, D., Streufert, S., & Fisk, W. J. (2012). Is CO2 an indoor pollutant? Direct effects of low-to-moderate CO2 concentrations on human decision-making performance. Environmental health perspectives, 120(12), 1671. Accessed at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548274/
- Rowe, D. (2003). A study of a mixed mode environment in 25 cellular offices at the University of Sydney. International Journal of Ventilation, 1(4), 53-64. Accessed at https://doi.org/10.1080/14733315.2003.11683644