[Greenbuilding] Relative humidity in heated houses

Corwyn corwyn at midcoast.com
Wed Oct 27 13:57:06 CDT 2010


On 10/27/2010 2:29 PM, John Straube wrote:
> Corwyn, can you please share with us the references to the health studies of lower RH exacerbating colds?
> I have never seen this evidence.  Ranges like "40-60" or "35-55" are bandied about, and there is graphs floating everywhere show that low RH is good for one thing or another (the most famous one is by Sterling, and has been widely debunked), but I, and others, have never seen the research although we have looked pretty hard.  ASHRAE does not, with all of its resources, have anything to offer to show this.  Currently I believe they say there is no lower limit to RH (because there is no data supporting that), but recommend over 25% (because that feels right, but also has no data).
> As far as I know, "low RH" starts to be noticeable to people, and possibly connected to health, when it is really low, like under 20%RH, perhaps even 10 or 15% and I surmise it is these types of "low" RHs that are a problem for people.   Eyes and noses and upper throat do evaporate lots of moisture at these low RH levels, and so people begin to feel itchy eyes, scratchy throats.

I appear to have been an idiot and not saved the reference.  I expect 
your google-fu is as strong as mine, so I despair of re-finding it, but 
I will try.

I start complaining about the dryness around 35%.

> I regularly run into MDs who suggest people with respiratory problems add humidifiers to their homes (and I get involved because of the disasterous results on the home) and challenge them for the data that supports this recommendation. Never ever got it.
> I do know that people with respiratory illness were often sent to sanatoriums in places like Arizona and New Mexico, which have very low RH's.  But that is anecdotal.

I suspect these are different respiratory conditions.

Thank You Kindly,

Corwyn

-- 
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
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topher at greenfret.com
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