Humidity and condensation

In cold weather, condensation forms quickly on bare windows and metal.

Excessive humidity is a common challenge for vandwellers and other nomads. In addition to discomfort, the resultant condensation can cause mold, mildew, and rust damage, damage to electronics, wood expansion, and reduced effectiveness of insulating materials (including blankets and sleeping bags).

Relative humidity of 25% to 60% is generally comfortable for humans. Insufficient humidity is only an issue in extremely dry climates or seasons, or with certain heat sources that dry out the air.

Causes of high humidity

Common causes of high humidity / condensation include:

• Environmental humidity: High natural humidity means that it's more difficult to reduce the humidity in your living space.
• Full-time habitation: Humidity due to constant habitation. Humans exhale about 300mL of water each day.
• Combustion of fuels: Propane or butane create water vapor when burned, as when cooking or heating.
• Cooking: Water vapor is released from food or liquids during cooking, most visibly during a boil.

Reducing sources of humidity

Relocation to a drier climate sounds like a severe response, but snowbirds often follow comfortable weather. Climate mobility is a distinct advantage that most nomads enjoy over those who live in conventional sticks-and-bricks residences.

When cooking, strategies to reduce humidity include: reducing cooking time or temperature when appropriate, choosing foods and recipes that release less liquid, cooking with electricity instead of water-producing fuels, or cooking outdoors. Things that steam should be covered (pots, cups, etc.). Coffee can be cold-brewed instead of heated to near-boiling. Teas should be steeped at lower temperatures, which varies by tea variety. Pre-cooked commercially canned and bottled foods generally do not need to be boiled when heated.

When heating water for water purification, it can be heated at temperatures lower than boiling for longer times. This saves energy and reduces humidity. See the water purification page for important details and safety considerations.

Removing excess humidity

After working to reduce sources of excess humidiy in your vehicle, next take steps to reduce the humidity itself:

Ventilation

Ventilation is a requirement for nearly all nomad vehicles. Roof vents are the most common solution for removing moisture in larger vehicles. Window vents, especially those with rain guards can be used to crack windows without allowing rain in.

Air conditioning

Your vehicle's air conditioner (or secondary air conditioner for your living space) will dehumidify the air as it runs. You can still do this if you don't need the air conditioner's cooling capability by running your heat and your air conditioner at the same time. Most vehicles HVAC systems allow you to use both at the same time; it won't hurt anything and it will dehumidify your air quickly. If you are using your vehicle's air conditioner, be sure that air recirculation is turned off unless it is extremely humid outside. If your air conditioner is pointed at your windows, it may cause condensation on the outside of the glass if the glass is colder than the ambient air.

Sacrificial window

If the exterior temperature is significantly colder than the interior, a closed "sacrificial window" may work as an unpowered option. Water will condense on an uninsulated exterior window (or metal surface) because it will be much colder, allowing the humidity in the van to be collected and used or disposed of. This approach is beneficial if you want to ventilate less.

Dry heat

Heating with diesel heaters or wood stoves will dry out your air.

Chemical dehumidification

Chemical dehumidification works for very small, confined areas (generally not your whole vehicle), but is expensive. Products containing calcium carbide (DampRid, etc.) or silica gel (Eva-Dry, etc.) may help control excessive moisture. A Dri-Z Air Dehumidifier and Dri-Z-Air 60-Ounce Refill may also work for you. 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! You may also have luck with silica gel cat litter, which can be purchased in bulk quantities.

Eva-Dry units are named after the cubic feet of space they are designed to handle. Example: the E-500 is made for 500 cubic feet, approximately 8x8x8'. (Units larger than 500 are Peltier or some other non-chemical technology.)

Dri-Z Air Dehumidifier

Widget:Products/Dri-Z Air Dehumidifier – Crystals turn from solid to liquid in the dry-z-air units. Dri-z-air removes moisture from the interiors of trailers and campers during periods of storage or lay-up. Keeps moisture from clothes, sheets, shoes, and more. Prevents condensation on windows, walls, and ceilings.

Electric dehumidification

In some cases an electric dehumidifier may be necessary, such as the Eva-dry Edv-1100. Some users drain the receptacle into a sink or other drain. Eva-Dry confirms the 12v adapter for this model passes 12v and not 9v; this should make it easier to wire from house power.

Peltier dehumidifiers are power-hungry and run constantly; the dehumidifier might best be used as an opportunity load. Video teardown of a typical Peltier dehumidifier

Increasing insufficient humidity

Evaporative coolers or ultrasonic misters may help improve the interior humidity.

Some or all of the content on this page was originally sourced from this page on RVWiki

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