Every time I go camping I'm usually only interested in wind, temperature, and if its going to storm or rain but i've read a couple of posts that talk about dew point and condensation. Does anyone have any information as far as what dew point would cause a lot of condensation to occur? I've always seen the dew point and humidity on weather reports but haven't been able to do much with it. thanks
Dew point is the temp where the moisture can't remain suspended in the air and falls out as condensation. It is a much better indication of moisture in the air than relative humidity. Higher dew point means more moisture in the air.
If the dew point is 50 and the temp only gets to 55 then there won't be much dew.
Here's another one I've been wrestling with . Frost Point . This comes into play when frost forms on the underside of a sock that some folks use for winter camping . The prevailing thought is that it is inevitable in temps aproaching zero F . I believe with the right material and insulation it can be avoided .
This is caused by the relatively warm moist air from exhalation encountering the cold material of the sock and sublimating directly from water vapor to frost .
As far as condensation occuring in a hammock or elsewhere this is from vapor barriers such as silnylon or mylar reflective sheets or closed cell pads trapping warm moist air which then encounters a surface cool enough to condense on .
Temp-due point spread is also good to pay attention to. If these two numbers get within 2 degrees F or 1 degree Celsius you have a much higher chance of fog or waking up with wet gear.
I don't know much about frost point. Your condensation point is dead on. Either keep the air under the tarp above dew point or keep everything vented well. A breeze will help keep condensation down even under dew point.Originally Posted by riverjoe
Here is a good definition of dewpoint. http://www.weatherquestions.com/What...emperature.htm
What is the dewpoint temperature?
The dewpoint temperature is the temperature at which the air can no longer "hold" all of the water vapor which is mixed with it, and some of the water vapor must condense into liquid water. The dew point is always lower than (or equal to) the air temperature.
it's not a measure of how much moisture is in the air. It indicates the temperature at which water vapor in the air will condense into droplets.
on a graph it is where the lines of temperature, pressure, and RH converge
You are right, but it's a better indication than relative humidity. RH changes as the temp changes, but the amount of moisture doesn't change.
Dew point is 3*F below air temp for every 10% change in relative humidity below 100% (so dew point is same as air temp at 100% relative humidity)
Ok ... Time to break out the psych charts class . You remember those . Quiz tomorrow .
http://edis.ifas.ufl.edu/ae406
Dew point is simple, it's the temperature below which the moisture in the air condenses out as dew or frost.
Managing it is not so simple.
For ambient air a lot of folks ventilate like mad to avoid condensation neglecting the fact that they are encouraging more moist air to come in and condense out their water load on any surface. Air below the dew point is a moisture source, not a moisture sink. That is why tightening up in a below dew point situation will result in condensation but it will be less condensation that opening up to a wet breeze. In marginal situations tightening up may also keep the microclimate above the dew point so the outside of the tarp gets wet but the inside does not.
The other shoe is the moisture one is exhaling and sweating out of one's body. Exhaled air is loaded with moisture at a temperature well above ambient most of the time. This air will have a higher dew point due to higher temp and higher relative humidity so it will form dew or frost at a higher temperature than the ambient air dew point predicts. Under those conditions the ambient air is a moisture sink so ventilation will pick up the condensed moisture helping to keep dry. In that case ventilation is good because helps keep dry.
If one knows what the predicted dew point and low for the night is then they can ventilate or batten down accordingly.
The other place this comes into play is in one's insulation. The temperature inside a piece of insulation changes with the thickness. For example if there is a 50 deg difference between skin temp and outside temp for 5 inches of insulation the temperature change will be 10 deg/inch. 4 inches into your insulation it will be 40 deg cooler than skin temp. If that is below the dew point moisture will be condensing out in that zone. If the outside of one's insulation is above the dew point then no moisture will condense in one's quilt. OTOH if using something like a CCF pad that is impervious to air movement inside the pad one may or may not condense out water between the pad and hammock depending on the dew point of the outside of the hammock and the porosity of the hammock. It does not take much moisture to be noticeable. That is one reason pads get a bad rap. You do not see the moisture in the quilt but you do see it on the hammock and pad.
YMMV
HYOH
Free advice worth what you paid for it. ;-)
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