Sunday, January 29, 2023


Ask Dave: Can I use a calcium chloride product to reduce moisture in RV?

Dear Dave,
Is a calcium chloride product like Dri-Z-Air adequate to dehumidify our RV? Or should we use a plug-in dehumidifier? —Bruce, 2017 Sunseeker

Dear Bruce,
I am not familiar with Dri-Z-Air so I went to their website. According to their MSDS (Material Safety Data Sheet), it is more than 90% calcium chloride, which is a crystal very similar to table salt. They recommend using one dehumidifier or tray every 10’ in an RV. The product claims to draw moisture to a 50% relative humidity, which is pretty good. You can find the product on Amazon here.

I have used DampRid for many years and found that to be very good at absorbing moisture, as well. According to their MSDS, it is 80%-90% calcium chloride, so I believe they are similar products. What I like about DampRid is the variety of products they have, from the hanging pack that can go in a closet to the larger buckets. They even have a moisture detection strip. You can find their products on Amazon as well here.

The downside of both products or anything else that uses calcium chloride as the base is there is not air movement with them. That means you can have pockets that can still get condensation, moisture, and mold such as cabinets, closets, under bed pedestals and corners around beds and furniture. Plus, calcium chloride products will only reduce moisture to 50% at max, which I would challenge unless you have about 10 buckets located throughout the RV. An electric dehumidifier draws in moist air and pushes dryer air out, and will reduce moisture down to 35% or lower.

What is the correct relative humidity?

Finding the right relative humidity for you is important and can vary. High humidity not only creates moisture but is a healthy environment for dust mites and mold. Low humidity creates dry air and increases the possibility of catching airborne viruses. It can also create dry skin and is irritating for owners that have skin rashes.

According to the National Asthma Council, the best relative humidity is between 30%-40%. However, mold will be inhibited under 70%

Tips to reduce humidity

The key to reducing humidity is limiting activities that create condensation, such as cooking, showering, and washing clothes. Hygrometers meter temperature and relative humidity. Find them on Amazon here.

Limit the amount of moisture in your rig by not boiling water or liquids when cooking. Limit or reduce showering time, and make sure your bathroom roof vent draws out steam and moisture. Ventilate the interior by using fans to move the air, and open overhead compartments or wardrobes to limit those pockets.

I sent Bruce a rough draft of this response and got this back, so I though I would update the post:

That’s awesome, Dave. Really thorough! I think, however, that there may be a difference between when we use our rig and when we store it. I’m looking at dehumidification because we had roof seal issues (that you have touched on before and what got me off my butt). I’m concerned that the styrofoam walls and ceiling have collected moisture. The RV Repair Shop that resealed our rig showed me a piece of foam out of another rig with more serious problems. The 10-square-foot piece of foam must have weighed over 50 pounds. I don’t know if I’m dragging around a bunch of weight as well as conducting a biology experiment. This might be another column.
Thanks so much for all you do and how well you do it. Take Good Care. —Bruce
So I sent him a note to look for a moisture meter like this one.
If the block foam insulation is saturated, I doubt the calcium chloride will be able to draw out much moisture as it is covered with luan paneling.

 You might also enjoy this from Dave 

RV ‘Gremlins’, Part 6: The final chapter—RV water leaks

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here


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California Travel Videos
1 month ago

Here is California where our PG&E electrical cost is 50 percent higher than the national average, we pay $.28 per 1,000 Watts per hour. The portable plug-in dehumidifier I purchased from Amazon a few years ago averages over 300 Watts per hour, so running 24 hours/day for the month in the wet winter days that’s a whopping $200 a month. Needless to say, even in other States it’s a good idea to consider electricity costs BEFORE the energy bill comes in the mail!

1 month ago

Electric dehumidifier is the way we go set at 40-50%. When not using the motorhome we park it in our barn. I put it on the kitchen countertop with the gray tank empty and valve closed, I drain it once a week into a 5 gallon bucket and water the flowers and bushes with it. We open all cabinets and drawers and prop the mattress up and partial open the sleeper sofa. We have never had a mold issue.

1 month ago

I have a question about using Damp Rid. Though not extremely expensive, why can’t normal calcium chloride (ice melter) be used? The Damp rid tubs just get tossed in the trash. More plastic pollution. I once did find a large Damp Rid refill container, but not always available.
I found a bag of ice melter that was 94% pure calcium chloride.

1 month ago

Tried Damp Rid and it works ok but we went to a electric dehumidifier which is way better and no mess. At home use a larger one located in shower with door open. When traveling we have a small portable on the counter that works well.

1 month ago

Living in an area with extreme high humidity at all times, We use an electric dehumidifier. Helps a lot.

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