====== Humidity ======

Relative humidity of 25%-60% is generally comfortable for humans.((https://en.wikipedia.org/wiki/Humidity#Human_comfort)) ((https://en.wikipedia.org/wiki/Thermal_comfort#Relative_humidity))
((https://www.engineeringtoolbox.com/relative-humidity-d_895.html))



===== excessive humidity =====

**Excessive humidity** is a common challenge for vandwellers.  It can cause mold/mildew, damage to electronics from water condensate, discomfort, wood expansion, and diminution of insulative properties of items like sleeping bags.  


Common causes of high humidity / condensation include:

==== full-time habitation ====

Humidity due to constant habitation can be reduced with increased ventilation, as with [[hvac:roof vent|roof vent]], assuming exterior humidity is lower than that of the interior.

[[http://amzn.to/2Dy19L3|Window vents]] can be used to crack windows without allowing rain in. 

A "sacrificial window" may work as an unpowered option.((http://www.cheaprvliving.com/forums/Thread-Condensation-AGAIN?pid=109944#pid109944))

Relocation to a drier climate sounds like a severe response, but [[camping:snowbirding|snowbirds]] often follow comfortable weather.
==== fossil fuels ====

Humidity due to use of [[fuel:propane]] or [[fuel:butane]] can be reduced with increased ventilation, reduced cooking/heating times, and the use of more efficient propane appliances to reduce overall consumption.

==== cooking ====

Water vapor is often released during cooking, most visibly during a boil.  Methods to reduce the production of water vapor include:

  * covering anything that steams:  pots, cups, etc.
  * reducing beverage temperatures if appropriate - coffee requires near-boiling temperatures but most other hot beverages do not. Green tea is generally steeped at 160F and black tea at 190F.
  * reducing food reheating temperatures if appropriate.  Already cooked commercial foods (canned or bottled foods) do not need to be boiled.
  * reducing water temperatures for drinking water sanitization if appropriate.  //Boiling// is the traditional method but this has more to do with knowing the water temperature without a thermometer.  For comparison, milk is pasteurized at 161F for 15 seconds or 145F for 30 minutes.((https://en.wikipedia.org/wiki/Pasteurization#Process)) Enteric bacteria, spores, and viruses are killed by sufficent time at 160F.((https://academic.oup.com/cid/article/34/3/355/388050))  If using **boiling as a reference point**, merely bringing the water to the boiling point is more than sufficient and holding the boil is "excessive".((https://academic.oup.com/cid/article/34/3/355/388050)) There is nothing magic about boiling.


==== dehumidifiers ====
Products containing calcium carbide ([[http://amzn.to/2DXyiNO|DampRid]], etc) or silica gel ([[http://amzn.to/2DoJDpg|Eva-Dry]], etc) may help control excessive moisture, particularly in very small or confined areas.  
[[http://amzn.to/2h8QeIO|{{ https://images-na.ssl-images-amazon.com/images/I/41j242B4RdL._AC_US160_.jpg}}]]
Some silica gel units can be "refreshed" by plugging them into a 110v socket whenever the color indicator advises.  This gently heats the gel and drives off the moisture, so do this somewhere other than your camper!((https://www.eva-dry.com/frequently-asked-questions))

Eva-Dry units are named after the cubic feet of space they are designed to handle.  Example: the
[[http://amzn.to/2DoJDpg|E-500]] is made for 500 cubic feet, approximately 8x8x8'.  Units larger than 500 are peltier or some other non-chemical technology.


In some cases [[http://amzn.to/2h8QeIO|an electric dehumidifier]] may be necessary.  Bitty recommends [[http://amzn.to/2gWtXyB|the Eva-dry Edv-1100]].((http://www.cheaprvliving.com/forums/Thread-Condensation-AGAIN?pid=109733#pid109733)) Some users drain the receptacle into a sink or other drain.((http://forums.sailboatowners.com/index.php?threads/12v-dehumidifier.167895/#post-1170395))
Eva-Dry confirms the [[https://www.eva-dry.com/dehumidifiers/edv-12v-power-cord/|12v adapter for this model]] passes 12v and not 9v;((https://boondockplan.wordpress.com/2016/12/06/eva-dry-12v-humidifadapter/)) this should make it easier to wire from [[electrical:12v:intro|house power]].

Peltier devices are power-hungry and run constantly; the dehumidifier might best be used as an [[electrical:solar:nonessential|opportunity load]].

Video:  [[https://www.youtube.com/watch?v=_hH-8KqQtys|teardown of a typical peltier dehumidifier]]






===== insufficient humidity =====

In some very dry regions humidity may be too low (=<20%)for comfort.  Evaporative coolers or ultrasonic misters may help improve the interior humidity.