Insulating a the Crew Cab Rear
One of the first things you will notice if you have purchased a Mercedes Benz or Freightliner Crew Cab van is that the rear of the vehicle is unfinished. It’s basically half of an empty van with literally no insulation or even siding. The first thing you will want to do with any van is to insulate it. This will keep you warmer in the winter and cooler in the summer keeping your internal temps more stable and allowing your HVAC to work less to keep up with the demand.
With any van that has no protection, if you carry any cargo that might shift, you risk the annoying pimple dimple outtie dents that can occur when something tips over and hits the metal panel of your fan from the inside.
Insulating a van has been done and written up by many folks. I’ll include some links at the bottom to some great posts about the subject.
There are many products and many approaches to insulation and we will share ours. But I think we can all agree it all starts with a sound deadening layer. We have used a few different products in our vehicles over the years and found many to be very similar. Obviously you can get different thicknesses but for the most part a simple 80mil (2mm) thickness is plenty. What you really want is easy installation, especially when getting to the hard to reach parts, and longevity. Something that will stick and not fall down in the heat of hot summer days or get brittle on really cold days up in the mountains in the dead of winter.
(the following is around what we do, but we’ve been inspired by many out there.
Thanks for the inspiration DIY Sprimter, Tom Clouse, Adventure wagon and others.)
Next we tackle the actual insulation:
First, Our stance is to NEVER use fiberglass insulation. All those glass fibers can create glass dust while you drive. It’s easy to go to your hardware store and just pick up that pink stuff. Not only can it cause respiratory issues but it holds moisture and easily creates a perfect environment for mold to grow. Just don’t do it.
In our opinion there are only two option for wall insulation. Thinsulate or Havlock Wool.
We prefer Thinsulate as it doesn’t hold water and is a hydrophobic insulation (won't absorb moisture).
more to come
Reflective insulation
more to come
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Vapor Barriers
There are two distinct camps here, those who favor Vapor Barriers and those are against Vapor Barriers.
Pass on the Vapor Barrier?
The metal walls of the van are already a perfect vapor barrier, by adding an interior vapor barrier you have now created a vapor barrier sandwich and any moisture that gets in between the two will be trapped with no way out.....and moisture can and will get in.
It's almost impossible to install a perfectly sealed inner vapor barrier, and even if you managed to do so there are still ways for moisture to get in. Moisture can get into the insulation space by changes in temperatures, changes in pressures (Driving over mountain passes or even closing doors), leaking door handles, leaking body trim clips, leaking fans, leaking windows etc etc. If and when moisture does get in you will want a way for the moisture to be able to escape.
Our take is to create partial vapor barriers along the walls but not on the ceiling.
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Avoiding Moisture
When we get our heaters fired up to stay warm and cozy, It's critical to control moisture any way you can to prevent mold formation and/or the dreaded "Funk" from taking over the inside of your van.
It’s not just about insulation - Vent Fans, Heaters & Cooking:
There are many ways moisture can get into your van...cooking with open flames, direct fired heaters (Buddy heaters), showers, bringing in wet cloths, leaking body trim clips, just breathing and sometimes its raining outside and your dealing with 100% humidity. We try and control moisture on any front that can keep the inside of the van as moisture free as possible. We are running a indirect fired diesel heater (Espar D2) so any combustion gasses/moisture are vented outside.
First simple rule: Try and avoid any direct fired heaters (Mr. Heater) as a byproduct of combustion is moisture and these heaters will add a lot of moisture to the inside of your van.
Second rule: Cook Outside We usually do all of our cooking outside but sometimes will fire up the Jetboil or backpack stove inside when needed, we need our coffee or some soups when it’s nasty outside. If so, we then crank up the roof vent. Even better if you have a vent directly above where you cook. (We only have powered Maxx Fan out back) Don’t forget to crack the side window accordingly to vent out the moisture produced from cooking.
Third rule: Keep the air flowing When sleeping we keep the fan above our bed on 10% exhaust (winter or summer, although summer may be higher speeds) and keep the front side window cracked open for a fresh air intake. The heater just runs more to keep the interior warm and the warm air exhausting out the top of the van helps carry out moisture produced from breathing while we sleep. We also have a lot of glass since our van has window on almost all panels. We cover all the windows with insulated magnetic window covers. This helps keep the interior warmer and keeps moisture from condensing on the glass over night.
If your running a heater in your van with no insulation then proper venting is even more important as you will be condensing a lot of moisture in the ceiling and walls and your van WILL develop the dreaded FUNK over time (A nasty musty oder). It’s common to add a cheap Chinese heater in you van with just a front window cracked and no roof vents. This is just not enough to prevent interior condensation. You will develop an unhealthy funk that can make you sick. Funk = mold.
Easy habit - Dehumidify:
When driving, leave the AC on (even if using heat) to capitalize on it's ability to act as a dehumidifier. This helps pull moisture out of the van. Cabin air flows through the AC evaporator where it comes in contact with the cold evaporator coils. This rapidly lowers the temperature of the air and causes moisture to condense (cold air holds less moisture than warm air). The water then flows out of the evaporator through the built in drain and drips out under the car. The cold dry air then passes over your heater core and is heated back up, now you have warm dry air 👍. This is why your AC automatically comes on when you turn on your defrost.
Driving with the AC on definatly helps but if we have been camping in the rain for several days I still find a little more is required.
When parked you can use a 110v dehumidifier or simply keep a bucket of Damp-Rid under the seat to help adsorb moisture. Damp rid is silica gel that passively absorbs moisture with no electricity needed, once they are used up they are disposable.
