How to Improve Air Quality in Buildings

How buildings manage air quality can impact health and the spread of disease. When I was in architecture school, a large 5-level room served as a grand collaborative learning space. But during the winter cold season, stressed, sleep-deprived students shared not only creative ideas, but also the current strain of seasonal cold. Given that we spend so much of our time indoors – about 90%-it’s not a surprise that how buildings are designed and operated can significantly impact our health.

Fast-forward 20 years, and we are seeing signs that the COVID pandemic has only heightened public awareness of this connection between buildings and health.

City initiatives to create parklets for outdoor dining are a direct application of studies showing that disease transmission is about 20 times less common outdoors than inside.
Over the last year, in our conversations with architects and owners about COVID mitigation and healthy buildings, air quality has been raised repeatedly.
Formal surveys mirror this concern. CBRE’s The Future of the Office Survey (September 2020) ranked indoor air quality 3rd in tenant priorities when evaluating office space.
Schools with older under-ventilated buildings are seeing more impetus now to upgrade older, neglected ventilation systems.

Fundamentally, a few basic strategies can improve air quality in buildings. Some of these strategies can mitigate infectious diseases, but also improve general air quality by removing other indoor contaminants such as dust, chemicals off-gassing from furniture and finishes, and colognes and perfumes.

Increased Ventilation

In buildings with a central mechanical ventilation (HVAC) system, increasing fresh air intake and reducing re-circulated indoor air can improve air quality unless the building is located in areas with polluted air. Increasing outdoor air dilutes and expels indoor contaminants, but requires more energy to heat the air in winter and cool the air in the summer. How exactly to increase outdoor air will require professional assessment of this energy trade-off, the ability of the existing system to comfortably condition the increased air, and the impact on system maintenance.

Naturally-ventilated buildings depend on doors, windows and air infiltration in the building envelope to provide fresh-air. In these buildings, occupants can improve air quality by opening windows manually.

Filtration

Air quality can also be improved through filtration. The level of filtration is designated by a MERV level, with a higher number providing better filtration.

ASHRAE, the technical society that provides standards for mechanical systems in buildings, currently recommends increasing building filtration levels to MERV 13 or MERV 14 if existing buildings can accommodate such a change.

Finer filters more effectively capture infectious aerosols, but more energy is needed to push air through these finer filters. In naturally ventilated buildings, standalone air purifiers can be used to clean the air.

Humidity

Proper humidity in buildings can also improve health. Microorganisms can grow in conditions that are too moist as with condensation in poorly insulated buildings. But spaces that are too dry are also problematic. Lower indoor humidity dries out our respiratory systems, allowing viruses to more easily infect us. Dry conditions also allow viruses to float more freely, rather than being captured in droplets that fall to the ground. Thus a middle range between 40% and 60% relative humidity is ideal for minimizing the spread of infectious disease.

Ultraviolet Light

A well-established, decades-old technology, ultraviolet germicidal irradiation (UVGI) can effectively inactivate microorganisms. Most effective around 265 nm (UVC), such systems can be installed in the upper part of rooms above 7 ft. Perhaps one of the upsides of the pandemic has been the increased public awareness of the connection between indoor spaces and our well-being. Even as COVID passes, hopefully, the trend towards making buildings healthier will continue.

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