Recent experience has shown that in many cases buildings designed to current minimum indoor air quality (IAQ) standards lack the performance to protect occupants effectively during infectious disease outbreaks and outdoor air events, such as wildfires. While there is growing recognition of this issue, there is also concern that improving IAQ standards and best practices will increase energy consumption.
For decades, the solution to healthy IAQ has been ventilation and introduction of outside air—e.g. dedicated exhaust to contain and discharge airborne contaminants generated by equipment, processes, kitchens, and restrooms and discharges are offset with fresh outdoor air. Unfortunately, this traditional means of providing good IAQ through ventilation with outdoor air assumes outdoor air is cleaner than the indoor air. However, this is often not the case, particularly during extreme airborne contamination events, such as wildfires. In order to preserve healthy indoor environments and prevent harmful exposure to employees, it is critical interior spaces are isolated from unhealthy outdoor contaminates, and any air that enters the building is sufficiently treated to remove these contaminants.
Filtration and air cleaning are effective means of controlling indoor air pollutants, particularly those associated with poor outdoor air quality. Air filtration or air cleaning can provide an important aide to, and in some cases a partial substitute for, outdoor air ventilation. See the ASHRAE Position Document on Filtration and Air Cleaning, which provides a detailed treatment of filtration and air cleaning alternatives, and when properly administered and maintained, can improve IAQ and energy performance. For additional information, download a copy of ASHRAE’s New IAQ Guide.
Additionally, new studies indicate it is more energy efficient to clean the air inside buildings than introduce outside air that must be conditioned (heated/cooled). Therefore, a solution to improve indoor air quality and meet energy consumption goals lies in utilizing high efficiency filters to clean air inside buildings. The Environmental Protection Agency (EPA) recommends a minimum of Minimum Efficiency Reporting Value (MERV) 13 filters for forced-air HVAC systems, and if possible, high efficiency particulate air-filters (HEPA). Read more about filter efficiency from the EPA.
The downside to a filter upgrade solution is not all HVAC equipment can accommodate the necessary high efficiency filtration, because it creates too much restriction and can result in system failure. Existing HVAC systems often require modification to realize the benefits of high efficiency filtration, which require advanced planning by subject matter experts and budgeting.
So, what does this mean for public agency facility managers? The new realities of these emerging IAQ issues should be addressed in the design phase of projects involving new construction or HVAC replacement. When designing new or updated HVAC systems, consider upgrading to incorporate high efficiency air filters and adding a means of isolating (closing) the HVAC fresh air intake to prevent dirty air from entering the building during extreme airborne contamination events, such as wildfires. If total system replacement is not an option, it is recommended that an agency consult with an HVAC professional to determine a system’s capacity for high efficiency filtration and recirculation capabilities prior to any modifications.