Ventilation. A term that most people outside of the HVAC world rarely heard until a few months ago. As the COVID-19 pandemic escalated, and the CDC and WHO finally started to recognize airborne transmission, ventilation quickly became a buzz word.
So why does ventilation matter? The virus that causes COVID-19 is spread through very small aerosols and droplets released in exhaled breath. There are mountains of evidence to show that these aerosols can be carried more than 6 feet in the air and could cause infection if they are inhaled. This is most likely to happen in indoor environments when the ventilation in a room is poor. The longer the period of time people spend in a space, the more likely the virus is to build up in the air and be inhaled, leading to infection.
Don’t Building Codes require a “safe” amount of ventilation? Not enough to quickly remove a virus from the air! After all, buildings were not designed to have air as clean as a research lab or operation room.
ASHRAE Standard 62.1 is the governing standard in the HVAC Industry when it comes to acceptable ventilation levels in commercial buildings. There are outdoor air requirements based on building type, occupancy level and even considerations for the quality of the outdoor air that is being brought in.
ASHRAE 62.2 is the standard that defines the roles of and minimum requirements for mechanical and natural ventilation systems and the building envelope intended to provide acceptable indoor air quality in residential buildings.
The 2019 edition of Standard 62.2 adds a compliance path that gives credit for particle filtration, distinguishing between balanced and unbalanced ventilation system interactions with natural infiltration, requiring compartmentalization limits for new multifamily dwellings, and allowing for single-point envelope leakage test results to be used when calculating infiltration credit.
However, most residential buildings are not new and even new one’s likely have local building codes that are not up to the 62.2-2019 standard.
In the vast majority of homes in the United States, there is no mechanical system supplying outside air (ventilation) indoors and exhausting indoor air outside. The only way homes are typically ventilated is by opening a window and/door, or by small amounts of air leaking through openings and cracks in the building walls or roof. Homes generally recirculate ALL indoor air through AC unit/ furnace filters when the heating or cooling system is operated.
The majority of the focus during this pandemic has been on commercial buildings with low ventilation. Offices, restaurants, schools, grocery stores, retail businesses are all spaces where we have identified that the risk of infection increases drastically due to shared air in a poorly ventilated space with an infected person.
Over the next few weeks, people will be spending just as much time, if not more, in their homes than these other spaces. It is important to recognize that the ventilation in your home is likely lower than a restaurant. If you have a group of friends or family over for dinner for a couple of hours, airborne aerosol virus particles from an infected person will build up inside with no path out of the home.
So what can you do? If spending time inside a house with people you do not live with is in your plans, there are some things you can do to make it safer.
While ventilation is important, it should always be used as a preventative measure in addition to social distancing, hand washing, wearing face coverings and limiting interactions altogether.