Comments on: Humidity, Health, and the Sterling Chart

By: Adam Stetten

Adam Stetten — Tue, 15 Feb 2022 17:02:22 +0000

Agreed David,
Often the moisture “we need” is leaving through some exhaust. Retaining what we can or should strategically is awesome. During cold snaps I will run the 3rd floor fan “on” for 30 minutes during “bath-time” and the home integrates it wonderfully, and much less noise for the bathers. I love how eco-bee has the “run fan for X minutes” button, so even though my wife doesn’t want the stove vent on we can mix the home.

By: Philip George Hayward

Philip George Hayward — Thu, 30 Jul 2020 21:38:44 +0000

The problem is indoors
The problem is indoors environments, therefore you can have a humid climate but still have dry indoors environments. One of the biggest problems is when HVAC systems recirculate the air internally, allowing it to get drier and drier, and allowing virus load to build up over time. There is a hypothesis that is unbreakable, about the spread of COVID-19.

Fresh air and high rates of indoor – outdoor air exchange greatly reduce transmission. A large number of people in the same indoors space for a prolonged time is a problem – in cities with crowded housing issues, imposing a lockdown actually creates a one-off spike in spread. I predicted this about London. The more vocal people are, breathing in and out, the greater the viral load. Hence parties are a problem, events in restaurants, indoor sports, singing, meat processing plants, etc.

The level of humidity inside is an important factor, but there are several factors as I describe. Each of them make the spread more or less bad; none of them are alone the problem or the solution.

“Contact” and surfaces and droplets from coughing etc have been over-rated in this pandemic. Almost all the spread has been via indoor environments and behavior, via airborne viruses (aerosols). The rate of “R” is a classic illustration of the limitations of an “average” when the data is comprised of outliers. This virus has not spread steadily from person to person in normal daily life at all, and the draconian restrictions on normal day to day life, is like carpet-bombing a country to eliminate its leadership – when a few drone strikes would solve the problem without all the collateral damage. Maurice de Hond does a good visual presentation here, contrasting the orthodox, wrong visual presentations of the rate of “R”, with how spread really occurs:

https://www.youtube.com/watch?v=WPM84WsJA7I&feature=youtu.be

By: Brian

Brian — Mon, 20 Jul 2020 01:39:18 +0000

Allison, you are a great
Allison, you are a great example of an ever questing mind. Always question received wisdom. This summer may remind people that whatever we do to modify indoor climate, the outdoor climate is going to be quite a moving target in the future. Talking on the phone to a person in Florida last week I realized the my outdoor temperature in Vermont was the same as hers – low 90's.

By: BJP

BJP — Fri, 17 Jul 2020 16:48:42 +0000

Great articles, especially
Great articles, especially like consequences of high MERV filters and low velocity ducts. However, should throw be reassessed? Throw/direction of throw (and return(s)) are quite important. Downflow may be the best, ceiling to floor, to prevent horizontal spread (worked in a tsetse fly lab that studied sleeping sickness, direction of flow was important). And, IAQ sensing separate filtration units (e.g., Dyson, etc.) may be better than dropping pressure/throw with a high MERV filter. As to humidity, the spray dryer effect is important too. I worked for P&G Europe on spray dryers to make powdered detergent and clothes dryers that vent into rooms (Europe has largely outlawed vented dryers as fire hazards). Low humidity results in rapid mass transfer, droplets at near 100% RH in lungs, will lose moisture and rapidly reduce in size in under a second, becoming more buoyant. As to clothes dryers, I ran tests on enzymes (individually smaller than SARS-CoV-2), which I collected in a room via air filtration. However, it is quite unlikely to find an enzyme “isolated”, same with SARS-CoV-2 (thus, the 0.125 micron size is probably not too important). Think about it, what is the likelihood that a human would exhale a single, isolated virus? Think about the chemistry/physics, your body is a bag of water, things are sticky (natural surfactants, etc.). All the talk about needing submicron filtration is, IMHO, overblown(noting I’ve seen people test positive for antibodies against enzymes they inhaled when not wearing respirators, while working with highly concentrated solutions from suppliers). I would guess that filtration of 1 micron particles is probably sufficient for most biologics (I also worked on chemical protection suits for the US Army, that was a different story). Many studies that “detect” SARS-CoV-2 are using genetic tests that will react with “flotsam”, i.e., harmless tiny pieces of SARS-CoV-2 virus (think “touch” DNA). No doubt, the reality is complicated. Time to reassess throw, reassess direction of flow, reassess use of separate air filtration units, reassess whether MERV 13 is really that important (or in fact quite detrimental to throw/FPM/CFM), reassess importance of humidity to avoid spray dryer effect, . . . . I believe HVAC experts, scientists and engineers will be the ones that make a great impact in helping biologists/medical doctors understand how we can hinder transmission in our indoor or other “enclosed” environments.

By: RM

RM — Mon, 13 Jul 2020 18:14:15 +0000

In reply to Curt Kinder. I have a pair of window
I have a pair of window shakers that can pull my leaky 1980s climate zone 2A home down to 45% given enough time. Both units are undersized so their running at 100% duty cycle all summer long helps.

By: Curt Kinder

Curt Kinder — Mon, 13 Jul 2020 04:24:53 +0000

Here in the hot humid
Here in the hot humid southeast (north Florida) I regard 45% RH as the “Holy Grail” humidity goal…It takes a high performance HVAC system in a well-sealed home to hit that number during cooling season (March – November).

Happily it rarely gets cold enough here for 45% RH to cause problems during our so-called “heating season” consisting of a few days in December, January, and February.

WHY DOES THIS SITE’S INANE CAPTCHA SYSTEM FORCE ME TO IDENTIFY MULTIPLE IMAGES / PANES WITH BIKES BUSSES WHATEVER?!?!

I’M SO DONE WITH THIS!

By: Dan Cullen

Dan Cullen — Mon, 13 Jul 2020 02:37:29 +0000

From by BIL the Doc: As an
From by BIL the Doc: As an ENT, I thought I would share my personal perspective. This information seems to add some credibility to my perspective. Most upper respiratory infections start with a viral illness, and then have secondary bacterial infections. In the past, I used to lecture on antibiotic resistant sinusitis and otitis media for which I researched the incidence and seasonal variations between infection rates in the southern US and northern US. Therefore, it is not surprising that COVID is more contagious in the south now and less so here in the north. Ever wonder why the COVID incidence has dropped in Wisconsin with many people ignoring social distancing and masking precautions. I suspect a lot has to do with the rate of mucociliary transport which is impaired dramatically by dehumidification with heavy use of air conditioning during the summers because of the oppressive heat in the south and forced air heating during our brutal winters in the north. We all stay too much indoors in dry environment during the winter and the south does the same now. The repeated changes of temperature and humidity is also detrimental to the health of the nasal mucosa. Not too surprising that the incidence of COVID infections is low here in the northern climates and increasing in the south this summer. In October the reverse will occur again. Maybe we should all be snowbirds. It may not have as much to do with ”opening up” or public policy as with our strengthened or weakened passive immunity to respiratory viruses. The entry way for respiratory viruses into our bodies are usually by touching our eyes or nose with contaminated hands to seed the nose, and more difficult to catch via airborne droplets, especially in a humidified environment. Interestingly, saliva seems to have some ability to inactivate viruses transmitted into the mouth. If a virus touches our nasal mucosa this time of the year, with a healthy mucosal gel blanket, which as part of our passive immune system which acts like a force field, the virus will be transported by our mucociliary transport mechanism within minutes into the stomach and inactivated by gastric acid, thereby never having a chance to enter or infect our respiratory epithelium. Think of the analogy of a flowing river versus a stagnant pond. Not only does masking help transmission of droplets to inanimate surfaces when someone speaks, coughs or sneezes, it more importantly prevents or reminds people from touching their nose. Another advantage rarely discussed is that masking also increases the intranasal humidity by preventing insensible water losses.

By: Dan Cullen

Dan Cullen — Sat, 11 Jul 2020 21:59:54 +0000

In reply to abailes. I believe that most of the
I believe that most of the time indoor storm windows like Indow will prevent condensation on all but the most extreme days during the heating season. The idiotic practice of using interior gyp board window sills should be illegal of course. And all homeowners should invest in a couple of thermo-hygrometers to keep an eye on indoor humidity.

By: Mark Siddall

Mark Siddall — Sat, 11 Jul 2020 08:20:18 +0000

In reply to abailes. If memory serves Joe
If memory serves Joe Lstiburek’s book Moisture Control Handbook mentions that low RH results in a suppressed immune system.

By: David Butler

David Butler — Sat, 11 Jul 2020 04:05:20 +0000

In reply to David Keefe. Previous comment should have
Previous comment should have been: "I avoid using spot ventilation for showers and when COOKING with water..."