As U.S. local and state governments continue to ease stay-at-home orders put in place in the spring to stem the spread of COVID-19, more and more people are starting to venture out into public spaces. And with this slow return to indoor activities such as dining, recreation, and going back to work, we see an increased awareness of—and concern for—indoor air quality and the potential health risks associated with it.
What remains an open question to scientists is whether or not COVID-19 can spread through airborne transmission, defined by the World Health Organization (WHO) as “the spread of an infectious agent caused by the dissemination of droplet nuclei (aerosols) that remain infectious when suspended in air over long distances and time.” In early July, the WHO stated
that COVID-19 predominantly spreads from person-to-person. However, WHO and the scientific community have been actively discussing and evaluating whether COVID-19 may also spread through the air over long distances as aerosols in the absence of aerosol-generating procedures (such as during medical procedures that generate aerosols), particularly in indoor settings with poor ventilation.
Regardless of what the science concludes concerning COVID-19, there is no doubt that good indoor air quality is vital for our overall health and safety, and studies have shown that it can have a sizable impact on student and worker productivity
as well. Two basic strategies for improving indoor air quality (IAQ) include diluting contaminated air via increased outdoor air volume and removing contaminants via high-efficiency filtration. Generally, two categories of contaminants exist, chemical and biological, and various dilution removal controls are combined to ensure proper ventilation. There are, however, energy-efficient and inefficient strategies that work together for accomplishing IAQ goals—and the efficient strategies come with potential incentives for customers who participate in utility energy efficiency programs.
Two top strategies contribute to an optimized energy-efficient ventilation system. When applied to the right situations, these strategies reduce energy use while providing an improved ventilation design. Additional benefits include potential utility incentives.
The first strategy involves the use of heat recovery or energy recovery ventilators (HRV/ERV). An HRV/ERV takes air normally exhausted from the building and passes it through an energy exchanger to extract energy and transfer it (precondition) to the incoming outdoor air. HRVs recover heat from the building’s exhaust air. ERVs transfer humidity. Both technologies reduce the energy needed by the building’s HVAC system, which is especially beneficial with the provision of more outdoor air (dilution) volume to improve indoor air quality in the space.
A second efficient ventilation strategy is known as HVAC load reduction (HLR). Regarding IAQ strategies, more filtered removal of contaminants from indoor air requires less dilution volume from outside air. HLR involves taking a portion of the return air and passing it through a sorbent filter composed of a powder that removes harmful chemical contaminants from the airstream before the air travels back through the system to get re-conditioned. This removal strategy reduces energy by reducing the volume of outdoor air requiring conditioning, with less pressure drop of other filtration mediums, while improving ventilation quality within the conditioned space.
Each building's specific needs and situations are unique, so the applicability of these strategies should be assessed on a case-by-case basis.
Effective and efficient filtration
Effective filtration is vital to achieving proper IAQ in buildings, especially since outdoor air in many urban settings is not exactly “fresh.” Like ventilation, there are efficient and inefficient air filtration systems.
According to ASHRAE
, “the fraction of particles removed from the air passing through a filter is termed 'filter efficiency' and is provided by the Minimum Efficiency Reporting Value (MERV) under standard conditions.” ASHRAE Standard 62.1-2019
specifies a minimum filtration efficiency of MERV 8 to clean the outdoor air before its introduction to occupied spaces for commercial applications when the building is in an area that exceeds the national standard or guideline for PM10 (inhalable particulate matter with a diameter of 10 microns or less). However, the standard recommends MERV 11 for buildings in areas that exceed the national standard or guideline for PM2.5. The National Air Filtration Association
cites MERV 13 as a best practice, and ASHRAE’s guidance on filtration concerning COVID-19 is to use MERV 13 or better. In today’s facilities, higher contaminant removal efficiency is a likely strategy for improving IAQ.
In traditional air filtration systems, as the filter efficiency increases, so does the static pressure, resulting in higher energy use and operating costs by the HVAC system. However, advancements in technology have made it possible to increase filter efficiency while saving energy. For example, the development of new filter media can deliver the same filter effectiveness as traditional media, but with reduced impact on static pressure. Buildings that use these more modern media can improve IAQ and reduce electricity costs simultaneously, making them eligible for potential utility incentives.
Earning incentives while improving IAQ
ICF is working closely with utilities and their customers to balance efficient ventilation and filtration in an energy-efficient way.
For example, ICF recently pre-approved a high-efficiency filtration project for a client’s custom energy efficiency program. This project replaces MERV 15 filters with energy savings filters that use a polarized media for particle and volatile organic compound (VOC) removal. The project, pre-approved for over $10,000 in incentives, saves the customer over 40,000 kWh and approximately $4,600 annually on their utility bill.
Through these and other energy-efficient programs
, ICF can help building operators and owners save energy while ensuring their buildings have proper IAQ—and earn incentives to do so.