Humidity in the coop and frostbite

[dacjohns]

Quote:
I think I know what you're trying to say but what you said isn't quite right. Back in the days when I was falling out of airplanes once we got under canopy are rate of descent was influenced by many things, humidity and temperature being two of them. In high humidity descent was faster because water molecules displaced other gaseous molecules and the air was less dense.

I believe a molecule of oxygen, O2 weighs more than a molecule of water, H2O.

http://www.engineeringtoolbox.com/molecular-mass-air-d_679.html

But no matter. On with the discussion.

 

[dacjohns]

Quote:
So did I but they all appeared to be repeating the same thing. Nothing to back it up.

 

[chookchick]

Thanks, Ivan, that makes sense--so what your saying, if I may try and simplify it, is that when the humidity is high in the coop, and there is not good ventilation up high, a kind of "fog" forms at the top of the coop and works its way down as the chickens breath and poo? Then this moisture coats their combs, and because of the conductivity of water, cools them much faster than the temperature drop alone would?

I've never seen hoar frost, but heard of it, what conditions lead to that?

I still think it would be possible to create SOME kind of chart, that would illustrate the correlation between frostbite, humidity and temperature, but I guess ventilation would also have to be worked into that also, and the number of chickens, size of house, and litter quality, and yada, yada, yada,....

 

[dacjohns]

OK. "High humidity" seems to be a factor.

What is high humidity?

 

[chookchick]

Okay, forget the "high humidity" part--when there is a lot of water vapor being produced in the coop with no where to go...it condenses out a lot more quickly when it is cold, right?

 

[dacjohns]

Quote:
Correct.

My "high humidity" wasn't directed towards anyone in particular. It is the theme of this thread and is in response to posts on other threads about frostbite.

 

[ivan3]

dacjohns wrote: What is high humidity?

Maximum amount of water vapor that can be transported by a given volume of air at a specific temperature and barometric pressure (not that I bother with the BP for purposes of coop maintenance).

ed:formatting​

 

[dacjohns]

Quote:
Maximum amount of water vapor that can be transported by a given volume of air at a specific temperature and barometric pressure (not that I bother with the BP for purposes of coop maintenance).

ed:formatting

Need numbers and a frame of reference. Relative humidity or actual amount of water vapor in a given volume of air and at what temperature? The term "high" is subjective. How high is high?

 

[ivan3]

chookchick wrote: Okay, forget the "high humidity" part--when there is a lot of water vapor being produced in the coop with no where to go...it condenses out a lot more quickly when it is cold, right?

It does indeed, but not uniformly or completely (nailheads - usually colder than the surrounding air - can grow some long hoar frost `cicles') if the chooks are continually adding water vapor and heat into an enclosed space at freezing temps, less than uniform results can occur (roo roosts in front area of coop, frostbite, roo roosts in back corner/no frostbite).

I'll just quote the Navy docs again as their observations square with mine:

b. Freezing, dry cold injuries are associated with extended exposure to subfreezing temperatures, usually 14 degrees F. or lower when the humidity is low

Relative humidity in the coop only allows one to make an assessment of how much more water vapor can reasonably be tolerated at an appropriate rate of exchange, for your specific setup.​

 

[RocketDad]

Quote:
For the purpose of this discussion, I'd say "higher than the humidity outside of the coop." I can't control the humidity of my environment, (other than by living here and not elsewhere) but by keeping enough ventilation I can make sure that the humidity in the coop is as low as possible.

I live in a very dry environment, and it's very apparent when the humidity is higher. Today was warmish, but it snowed a little, so the humidity is up to about 90% this evening. Part of that is the temperature drop since sunset.