Page 53 - Green Builder July-August 2020 Issue
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as Broan, Panasonic or Carrier. will not be damaged by high-performance you are changing the air in the room (with
Innovative Solutions for High-Performance Homes
Innov a tiv e Solutions f or High-P erf orma nce Homes The reason you are installing an HRV MERV lters. Trane makes one called the ventilation) three times per hour. You’re
(or energy recovery ventilator [ERV] in hot Hyperion, for example, that will do the job. looking at a formula something like this:
climates) is to save energy and maintain It also allows you to add a UV light inside H = 9,600 cu. ft. X 3 per hr. X 47 (grams of
comfort. Blasting cfm of fresh air into the the double cabinet. water per pound) = 14 lbs. of water per hour,
room with a standard one-way fan system, It should be noted, however, that some . cu. ft. per lb. X , grains/lb
rather than an HRV or ERV, can create a indoor air experts have suggested that One gallon of water weighs . pounds. So,
pressure imbalance by pulling air from the recirculation systems should not be used you would need about . gallons of water
garage below or via other appliances. at all in public buildings to control virus per hour introduced to this space to achieve a
Now that you have the diffusion spread. The verdict on this is still out. They virus-unfriendly humidity level of percent.
component of the necessary ventilation premise this advice on the fact that many Note that the more often you exchange the air
installed, let’s move on to ltration. building managers will simply run their in the room, the greater the volume of water
existing ventilation system more aggressively. you need to introduce to the space. If you
2. FILTER AND BURN—BECAUSE But these lack the requisite lters to clean choose the best case scenario of exchanging
VIRUS PARTICLES ARE SMALL infections from the air. My suggestions for indoor and outdoor air completely times
Next on the risk reduction list: Air recircu- recycled air filtration are based on CDC per hour, you will need to add . gallons of
lation that includes ltration, backed up by guidelines for hospitals, but you could also water per hour on a cold winter day.
UV lights. take a more-conservative approach and use
Removing most airborne COVID- HRV/ERV technology exclusively to avoid any DEFENSIVE, NOT FAIL-PROOF
particles is possible only with high-e£ciency recycling of air and replace all air in the room I’ve only addressed one aspect of how to
Minimum Efficiency Reporting Value or times per hour with outdoor air. manage COVID- indoors—the airborne
(MERV) or high-e£ciency particulate air version of the virus. Regular cleaning of
(HEPA) lters, due to the extremely small 3. HUMIDIFY—BECAUSE VIRUS surfaces and bathrooms, and many other
size of virions (virus particles). These may PARTICLES FLY WHEN IT’S DRY protocols, must also be followed to reduce
slow the air¥ow so much as to make the Research by Dr. Stephanie Taylor suggests contagion risk. No defensive measure can
system ine¦ective, however. An alternative that when indoor air is dry, airborne drops completely defuse the coronavirus threat.
is to use a MERV lter, which will grab of water and flakes of skin that contain But this article, based on CDC standards for
most of the water droplets COVID- uses as virions and bacteria stay airborne longer hospitals, gives you a good idea of what’s
a piggyback vehicle. and travel farther, and tend to be resilient involved if you want to make part of a house
These lters should not be relied upon as enough to remain infectious. Humidity as safe as possible for isolating a family
a percent solution, however. The good should be kept between percent and member with COVID´ or some other viral
news is that based on our target ventilation percent. Anything lower than percent and disease spread through the air. GB
level of recirculating exchanges per hour, viral risks increase dramatically.
free-¥oating particles will have numerous In one recent study of how children REFERENCE ITEMS:
passes at the lter media. The bad news is get sick from indoor air at school, a team
that these ultra- ne MERV lters may need at the Mayo Clinic humidified half of ■ CBS Boston: “Sharing Enclosed Space
frequent replacement, as they can quickly the classrooms in a preschool and left Leads to ‘Massive Spread’ of Coronavirus”
become clogged if the room is dusty or the other half alone over three months ■ Green Building Law Update: “COVID-19 and
contains other airborne pollutants such as during the winter. According to a report in the Risk from Recirculated Air in Buildings”
skin ¥akes or pollen. Cleanroom Technology, influenza-related ■ Live Science: “Face masks may reduce
Another important piece of filtration absenteeism in the humidi ed classrooms COVID-19 spread by 85 percent”
technology is ultraviolet (UV) lighting. was two-thirds lower than in the standard ■ Centers for Disease Control and
Although these lights are unsafe for human classrooms. Prevention: “Ventilation requirements for
exposure, they will kill viruses and bacteria, How much water does it take to humidify areas affecting patient care in hospitals
depending on how fast the air¥ow is, and a room such as our , cubic foot in-law and outpatient facilities”
should be installed inside the ductwork of apartment? That depends on several factors, ■ Iaqsource.com: “Alternate Ways to Size
the recirculating air lter. including the number of air changes per hour ERVs/HRVs”
Keep in mind that on top of HRV air ventilating the space, and the temperature ■ Kendeda Fund Living Building Chronicle:
exchange, you must create the substantial and humidity of outdoor exchange air. So, “COVID crisis cries for higher humidity in
airflow of air changes per hour. How for example, for a cold climate room (outdoor buildings”
much air do you need? Use the same formula temperature °F, desired indoor temp °F, ■ Cleanroom Technology: “COVID-19: Testing
we did for the HRV above: ,/ x . at percent relative humidity), which for surface and air presence.”
That’s a whopping , cfm. To achieve is feet long, feet wide, with -foot ■ Humidity Source: Introduction to Humidity
this, you will need something like an air ceilings, you start with , cubic feet. Let’s ■ Green Builder: “The Pandemic Resistant
handler system, with a powerful fan that assume, based on good ventilation practices, Bathroom”
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