Page 52 - Green Builder July-August 2020 Issue
P. 52
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Innovative Solutions for High-Performance Homes
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Behind Closed Doors:
Taking on COVID-19 with Ventilation,
Filtration and Humidity
As schools and businesses struggle to open, scientists warn that the
coronavirus may be airborne. Here’s how to minimize the risk.
BY MATT POWER recommendations) that could be applied
ASED ON WHAT we now know immediately to any indoor space. For exam-
about the coronavirus, enclosed ple, to achieve the air-clearing performance
spaces without proper ventilation of an ER waiting room, the minimum air
create the condition for airborne exchange with the outdoors should be two
B coronavirus spread. times per hour.
Why? Because of the way the COVID- But this is just part of the equation. Along
virus infection works. Particles need to with this air exchange, the CDC recommends
achieve a critical mass before successfully additional exchanges of indoor air. What
infecting a host, a scenario most likely when that means is that air inside the room
air is static and dry, and particles are being recirculates through a lter system a dozen
introduced repeatedly. And while masks and times over the same period. We will look at
good hygiene denitely reduce transmission ltration below, but for now, let’s focus on
rates, other factors are at least as important, the ventilation component.
including humidity levels, speed or air Let’s assume, for simplicity’s sake, that
exchange, lters and virus-killing lights. we are clearing the air in an open oorplan
No mechanical system is guaranteed to in-law suite above a garage. It has a forced
reduce infection rate to absolute zero. If hot water heating system with radiators,
masks, eye gear and social distance lower and is located in a cold climate. The room’s
infection rates to less than percent in health dimensions are feet long and feet
care settings (i.e., hospital rooms), adjusting wide, with -foot ceilings, amounting to
the way indoor air functions can chip away at , cubic feet of airspace.
the remaining last percent of risk. The easiest way to increase the overall
Here are three building science ventilation is to add a standalone heat
adjustments that can reduce the risk of recovery ventilator (HRV). This can be
airborne coronavirus spread indoors: mounted in a closet, inside the ceiling, or
even on the wall. To size it, divide the cubic
1. VENTILATE—BECAUSE STATIC feet of space by , and multiply by (air
AIR KILLS changes per hour). This gives you part of the
One key finding in coronavirus research CREDIT: COURTESY OF TRANE minimum cubic feet per minute (CFM)
is that infection is typically not one par- requirement for the space. So, our classroom
ticle, but a buildup of airborne particles requires ,/ x , or cfm of airow.
after several minutes near an infected per- Quiet powerhouse. Trane’s Hyperion air handler This is a larger volume of airow than
son. The Centers for Disease Control and can move air at high enough CFM to meet most residential HRV units, but you can nd
Prevention (CDC) has created guidelines hospital standards for filtration and dispersion models with this capacity, or simply install
for hospital ventilation (based on AIA in homes and other buildings. two separate units from companies such
50 GREEN BUILDER July/August 2020 www.greenbuildermedia.com
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