The stay-at-home orders issued during the coronavirus outbreak have a reason: residential buildings are considered the safest places during the pandemic. Single-family dwellings are especially safe, since there are no common areas. However, homes are not 100% safe from COVID-19, and ASHRAE has published prevention measures to make them safer.
Homeowners should follow the guidance provided by health authorities like the Centers for Disease Control and Prevention (CDC). However, a well-designed and well-maintained HVAC system will further reduce the risk of COVID-19 transmission.
Just like in commercial buildings, ASHRAE does not recommend shutting down the HVAC system, in spite of the potential savings. Increased ventilation will minimize the risk of infection if the virus manages to enter the dwelling. Keeping thermal comfort is also important, since the discomfort caused by high and low temperatures seems to weaken the immune system.
You can reduce the risk of COVID-19 with an HVAC filter upgrade and UV disinfection.
Upgrading the Filters in Residential HVAC Systems
Coronaviruses and other airborne germs can be captured with high-efficiency filters in central HVAC systems. According to ASHRAE, residential 1-inch filters can normally be upgraded to MERV 13, and 2-inch filters can be upgraded to MERV 16.
- Keep in mind that filters are only effective when air is being moved through them.
- HVAC engineers recommend leaving the fan on 24/7 if possible, even when space heating and cooling systems are off.
When mechanical ventilation systems supply outdoor air, there is a very low risk of introducing coronavirus into the dwelling. For this reason, the outdoor air intake filter does not normally require an upgrade. The only exceptions are when the air intake is close to another building’s exhaust, or close to a place where many people gather. In most cases, upgrading the outdoor air filter will only waste fan power with no benefit in return.
Energy recovery ventilators can normally continue operating, as long as they are well designed and maintained. However, an ERV with excessive leakage between the supply and exhaust should be bypassed, until it can be fixed.
Toilet fans should be kept in operation, since droplets with germs may be released when toilets are flushed. To minimize this effect, toilet lids should be closed before flushing, and kept closed.
Using UV Disinfection Against Coronavirus in Homes
Ultraviolet germicidal irradiation (UVGI) is recommended in residential settings, as long as the unit does not produce ozone. We tend to see ozone as a beneficial substance, since the atmosphere’s ozone layer protects us from harmful radiation. However, ground-level ozone is considered a pollutant, since it causes respiratory irritation and pain. The best recommendation is getting a UVGI system that meets UL Standard 2998 - Environmental Claim Validation Procedure (ECVP) for Zero Ozone Emissions from Air Cleaners.
Sunlight may help disinfect surfaces, since it contains ultraviolet radiation. However, this has not been verified by research in the case of COVID-19. However, allowing daylight into the dwelling can complement UVGI.
Additional Recommendations Against COVID-19 in Homes
The ASHRAE Standard 62.2 covers ventilation and indoor air quality in homes, while Standard 62.1 is used for commercial buildings. However, working from home can change the ventilation needs of dwellings.
- Standard 62.2 is enough for office work, but Standard 62.1 is recommended for light industrial activity, such as soldering and heavy-duty laser printing.
- Before using homes or apartments for semi-industrial work, an HVAC system should check if the ventilation system is suitable.
Portable air cleaners can be used, but they must have a high-efficiency filter to be effective against coronavirus and other airborne pathogens. The filter should be at least MERV 13, and HEPA is preferred. Units that combine filtration with UV air disinfection are the most effective.
In multifamily buildings, utility penetrations can be sealed to prevent air leakage from common areas or other dwellings. The P-traps and U-traps of plumbing fixtures must also be kept full to prevent the spread of germs and conserve air quality.