Moisture and odor problems, if left unchecked, can mar your motorhome’s interior.
By Mark Quasius, F333630
July 2015
Any home can be beset by excessive moisture and odors. But those problems raise special concerns in a motorhome.
Odors from cooking, smoking, or the family pet can be heightened when confined to a small living area. In addition, excessive moisture that accumulates from the outside air, as well as from breathing and cooking in a motorhome, leads to condensation, which can damage the RV. Fortunately, odors and moisture can be managed so a motorhome’s interior remains clean, dry, and comfortable.
If you don’t allow excessive moisture to accumulate, you won’t have to remove it later. Prevention, therefore, is the best defense.
Moisture builds up in a motorhome’s interior air as a result of people exhaling and engaging in everyday activities such as showering and cooking. Much moisture can be eliminated by exchanging the interior air for some fresh outside air. Ceiling vent fans do an excellent job of removing air from the coach, but a window or a second vent must be cracked open to replenish the air. Unfortunately, while removing the air, the vents also are expelling heat, so on cool days the furnace has to run more often.
Ideally, vent fans should be used when the heavy “moisture polluters” are active. Turning the vent fan on while taking a shower or while cooking helps to reduce moisture buildup within the coach, as well as to minimize cooking odors. Many of us have awoken on a cool morning, opened the front drapes or shades, and seen the condensation that formed on the inside of the cold windshield. Keeping a vent cover open slightly overnight will help to remove moisture and to minimize windshield condensation, without too much heat loss. There’s no need to run the fan all night.
Farewell To Smells
Odors also can be prevented. The inside of a holding tank — even a gray water tank — can be a major offender if those odors enter the coach interior. Sink and shower traps can dry out if not used frequently, allowing odors from the holding tank to waft back up into the motorhome’s interior. Smells also can come from bacteria growing in the trap and tank. Filling the trap with water will prevent odors from backing up through it. Adding a bit of baking soda to the water will help to eliminate odor buildup, too.
The holding tanks are vented, but some assistance may be needed to prevent odors from seeping into the RV’s living area. Venturi vent stack covers, which rely on differences in air pressure to pull odors up and away, help evacuate the holding tank vapors while a coach moves down the road. Products such as the Camco Cyclone RV holding tank vent go a step further; the Cyclone works well while the motorhome is parked, because the wind pivots the hood to create the same Venturi effect. Another product, from 360 Products, is designed to eliminate holding tank odors without moving parts. The 360 Siphon creates a negative pressure in the holding tanks that results in a natural updraft. Lippert Components Inc. recently finalized an exclusive deal with 360 Products to make, sell, and distribute the 360 Siphon to the RV industry.
Certain odors are especially hard to eliminate, such as cigarette smoke. The best solution: Don’t smoke in the RV. Pet odors tend to congregate in carpeting. Frequent vacuuming and occasional steam cleaning are recommended. Air fresheners help, but they merely mask odors rather than remove them. But to remove odors that have a foothold in your RV, you might consider Bad Air Sponge, which is marketed as the most powerful odor removal substance.
Bad Air Sponge has been used as an air freshener in Amtrak trains and other rail facilities as well as the Smithsonian Institution. It also helped remove smoke odors after the 1993 World Trade Center bombing.
According to the Bad Air Sponge website, the semi-solid gel contains activated charcoal and reagents that absorb, neutralize, and alter undesirable odors and fumes. The product is activated by removing the lid of its plastic container. Ejecting the product onto the overturned lid improves its effectiveness. The product, which gets smaller as it reacts with airborne odors, lasts from 30 to 150 days, depending on the strength of the odors and the size of the area to be neutralized. Bad Air Sponge is natural and nontoxic, so it reportedly is safe to use around pets or children. It is also water-soluble, so it cleans up easily if it gets on fabric or upholstery. It has a shelf life of two years in the unopened canister.
Other products rely on enzymes to eliminate odors. Enzymes, which are a type of protein composed of amino acids, remove odors by causing a biological or chemical reaction. Enzyme-based air fresheners generally are available in spray bottles and perform well in removing pet odors from the air.
I have had excellent results using Biokleen’s Bac-Out Stain and Odor Remover, as well as Bac-Out Fresh spray, but many other brands are available. Keep in mind that enzymes have a short shelf life. A product more than a year old loses its effectiveness, so don’t overbuy and stock up. Use only freshly dated products.
Moisture Removal
To remove moisture from a motorhome, the choices are a mechanical dehumidifier or a chemical desiccant system.
Mechanical systems are compressor-based, like typical residential dehumidifiers. The compressor operates on the same principle as an air-conditioning system. A compressor pumps refrigerant through a closed loop containing an evaporator and condenser. Once the humid air passes through the evaporator, the moisture condenses and drains into a water tank.
Such systems do not use desiccants that may need replacement, but they do require a fair amount of electricity. They also don’t work well in low temperatures, because their efficiency drops as the ambient temperature decreases. It can be common for dehumidifiers to freeze up in temperatures as high as 50 degrees, which makes them a less-than-ideal choice for cold climates. In some RV situations where the moisture load is light and the temperature isn’t too cold, a pair of small, compact units such as the Eva-Dry 1100 Petite dehumidifier can be very effective. In fact, we operate two in our motorhome when it’s not in use and parked in the driveway.
Desiccant-based systems eliminate the electrical and mechanical components and use a chemical compound to remove moisture from the air. Products such as Dri-Z-Air contain packets of desiccant crystals that absorb moisture and allow it to settle in the bottom of a canister. This is basically a calcium-chloride salt product, so you don’t want it to come into contact with metal or other surfaces that can be damaged by salt. Once the product is used up, the media is disposed of and the water in the canister is emptied. Refill packets allow for reuse of the container.
A better solution is a renewable desiccant such as H2Out space dryers. These units use silica gel, which is similar to what’s in those “Do Not Eat” pouches inside pill bottles and other products that must be kept moisture-free. But the H2Out product kicks it up a notch. Silica gel can absorb up to one-third its weight in water vapor, which is about 35 percent more than typical desiccant clays.
H2Out containers come in various sizes and can be placed in cabinets or just left in the open. The blue beads turn pink with use and typically last four to six weeks. The moisture is absorbed into the media, so no drain pan or catch bowl is required. The silica gel is enclosed in a perforated aluminum housing that prevents it from being ingested accidentally. Once the media is saturated, it can be regenerated simply by placing the unit in an oven (three hours for an electric oven; two hours for convection and toaster ovens). After the unit has cooled, it is ready to be reused. The units will last for many years as long as they are recharged when necessary.
An interesting hybrid system recently was introduced by Eva-Dry. The EVD-4000 is a rotary desiccant dehumidifier that blends the benefits of desiccant with a mechanical dehumidifier. It is the first product to use rotary desiccant technology to provide high-volume dehumidification without a compressor. It also includes a built-in ionizer and bacteria-killing filter to improve air quality.
With no noisy compressor, the unit runs quietly yet can treat up to 4,000 cubic feet of air, which easily covers even the largest motorhome. The water tank holds two liters; a hose connection is available that allows water to drain directly into a sink for unattended operation over longer periods. The humid air passes through a desiccant rotor, which absorbs the moisture. A heater then removes the moisture and runs it through a condenser, where it liquefies and drains into the tank.
Unlike compressor-based systems, the rotary desiccant system operates efficiently at low temperatures without freezing up. An additional benefit is the adjustable output louvers, which can direct the dry output airflow to wet clothes on a drying rack. The desiccant wheel does not need to be replaced, but it will lose 10 percent to 15 percent of its efficiency after about four to five years of use. Most owners won’t even notice.
Off-Season Storage
The need for odor and moisture control is greatest when a motorhome is closed up and placed in storage during the off-season. Mold, mildew, and bacteria love to grow in enclosed spaces where the air is not refreshed.
The best prevention is to thoroughly clean the coach before storing it. Vacuum and steam clean the carpet to remove any soils or organic matter. Remove all perishable food from the cabinets and refrigerator. Even nonperishable food items, such as crackers, may be a target for rodents, so it’s best to remove them as well.
Clean the interior of the refrigerator with a good disinfecting cleaner, such as Lysol or Clorox Anywhere, and leave the doors open to allow for air circulation. Leave cabinet doors open as well to prevent bacteria or mold growth. A box of baking soda in the fridge will help to absorb odors. Molds and bacteria need moisture, so placing desiccant units, such as those from H2Out, in strategic locations will help keep the air dry. If the motorhome is kept in inside storage in a temperate climate, open the ceiling vents a bit to allow some air exchange. However, if the climate is overly humid or cold, close the vents.
Keeping your motorhome odor- and moisture-free makes for a much more enjoyable environment and helps prevent mold and mildew damage. It will also keep your RV in the best possible condition for resale time.