Page 48 - Green Builder May-June 2020 Issue

airflow through the filter impacts how much
of the virus it collects. The example below
shows that at slower airspeeds, a MERV 12
filter is much more effective (with “1” being
100% effective).
Another unanswered question about fil-
ters is whether virus particles, once trapped,
will stay lodged in the filter matrix long
enough for them to die naturally. We know,
for example, that COVID-19 can survive for
several days on some surfaces. If the air-
flow is suddenly changed, could it dislodge
a deadly particle? No one seems to know.
And finally, there’s the question of in-
room filter performance, versus built-in
HVAC systems. Depending on the size of
the unit, its rated CADR (clean-air delivery
rate) rating (350 is considered good) and
the amount of particles captured will vary
widely.
I have tested ionizing type standalone
filters and standalone HEPA filters in my
own home using an Awair air sensor to mea-
sure their effect, and neither seems to have
much impact on the amount of particulate
in the air. I would definitely recommend
an integrated HVAC filter system over an
aftermarket product, with the caveat that if CREDIT: NAFA
you want to isolate a bedroom or sick room, Speed matters. Different types of MERV filters follow a general, identical path toward powerful job
you’ll need a way to zone it separately. In performance.
any case, filtration alone is not enough to
tackle a serious threat like coronavirus. You with filtration. In other words, by constantly a surface ruin your week, or your life. GB
also need diffusion. diffusing the air while you filter it results in
fewer particles to capture. This gives filters a FOR MORE INFORMATION:
FILTRATION PLUS DIFFUSION higher chance of catching virions that could ■ Science Daily: “One Virus Particle is
Building codes related to indoor air quality make you sick. A good product candidate for Enough to Cause Infectious Diseases”
aim to maintain acceptable indoor air qual- ventilating in this manner would be one of Research Gate: “Viral Penetration of
■
ity, not to scrub away every risky particle. Panasonic’s small FV-04VE1 energy recov- High Efficiency Particulate Air (HEPA)
For builders, that typically means meeting ery ventilator units. These run continuously, Filters”
the ASHRAE 62.2 ventilation requirement. replacing stale air with fresh air, although
■ U.S. Department of Energy: “ASHRAE
This results in a certain number of air exhaust-only bath fans or range hoods can Standard 62.2. Ventilation and Acceptable
changes per hour (ACH) in the home. be used to keep air moving. Indoor Air Quality in Low-Rise Residential
Newer homes operating under this No matter how good your air diffusion Buildings”
requirement already have basic air diffusion and defiltration, continue to practice sani- International Business Links: “Solution &
in place. Many older homes do not. It’s key tation and isolation protocols. Don’t let a ■ Relief to the COVID-19 Pandemic”
that this capability be used in combination single rogue virion that lands invisibly on

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