Would a strong mildew smell be a dealbreaker for you?

[SoulRaven]

Doesn't matter if it's a cargo van or a window van. The insulation that is put in the conversion vans is inferior at best and the design layout they use takes up ever so much space that is wasted. Any van I've seen that's over a few years old could probably do best with a complete strip of the interior carpet/floor mats and anything that was put inside of it on the walls anyways.

If all the windows are what a person wants then buying a window van makes sense. I've had both and truthfully all the windows just meant more heat entry on a hot day unless you block them up with reflectix. If you do that you defeat the purpose of having a window van and you may as well have bought a cargo van. OTOH it's nice to have all those windows to look out of on a nice day or sitting inside on a rainy day.

When shopping for a van there are far more important things to consider than how many windows it does or doesn't have....like mechanical and body condition, mileage and price for starters! Windows can always be added if you really need them.

Now if I was buying a motorhome, I'd be way more picky about the number, size and placement of the windows!!

None of the insulation designs that I see posted anywhere are good for either you or your vehicle, and most conversion vans started out life as cargo vans, which explains their poor MPG and mold/rust problems.

As far as covering windows to keep the heat out, that's what shade is for.

In a house, the insulation is vented.  This is the only proper way to do it.  A vehicle is a much more challenging job than a house due to condensation on the inside of the metal skin, ceiling, and floor.  It is impossible to prevent this condensation from occurring, but it is very easy to trap it, allowing it to cause mold and rust.

If you look in most passenger vehicles, they will have weep holes to accommodate the air circulation to the interior skin and also drain off any accumulated water.  If these get blocked, that is when you start getting the rust at the bottoms of the doors and rocker panels.  It is almost impossible to add these later, because unless you can get to the inside to paint it, you will wind up with exposed metal, which of course will lead to rust issues.  Cargo vans don't typically have these. 

If you can't vent the interior skin and insulation to the outside, then it has to be vented to the inside, but to have a successful installation, it HAS to be vented.

If you look at a passenger vehicle, they will typically have a heavy fibrous, wicking, mold/mildew proof pad on the floor, topped by carpet.  These are designed to wick the moisture away from the skin and up through the carpet to dry.  You're not going to improve on that system in any way.  The heavy paper type material you will find inside the interior panels, is also a wicking material to draw that moisture away from the metal skin.  The vehicle manufacturers have spent millions on perfecting the solutions to moisture and insulation problems to insure the comfort of passengers.  Anybody that thinks they can improve upon this is only fooling themselves and others.

The semi dead air space created between the interior panels and the outer skin is in itself good insulation.  One of the simple facts that never get talked about much is that all important air space for the insulation to work properly.  The truth is that the dead air space is what IS providing the insulating quality, not the insulation they want to sell you.

 

[highdesertranger]

off grid I have to respectfully disagree about the factory under carpet insulation. from what I have found over the years is once it gets soaked it never dries out and mold I have seen it blacker than the night with mold. you can't even remove it in one piece it is so rotten that it just come out in handfuls. it also sticks to the floor where the floor has rusted because it's been soaked for so long. I have seen this on many different vehicles for many different reasons. highdesertranger

 

[akrvbob]

I disagree with just about everything OffGrid said. My experience has been just the opposite.
Bob

 

[offroad]

Trying to talk through the science. Room temperature interior air with 60% humidity starting point. Then the temperature increases to 90F plus while vehicle is parked, due to greenhouse effect. Air expands. Pushes humidity filled air outside, humidity drops inside.

Reverse happens for cooling. But are seals not preventing air from coming in? Out pathway is easier than in pathway?

Is the net effect a drying interior over time? Assuming no rainwater leaks ?

 

[Almost There]

Trying to talk through the science. Room temperature interior air with 60% humidity starting point. Then the temperature increases to 90F plus while vehicle is parked, due to greenhouse effect. Air expands. Pushes humidity filled air outside, humidity drops inside.  

Reverse happens for cooling. But are seals not preventing air from coming in?  Out pathway is easier than in pathway?

Is the net effect a drying interior over time? Assuming no rainwater leaks ?

That science only works for moving air such as the open space inside the van.

Where it doesn't work is where moisture is trapped in materials that absorb small amounts of moisture well but are protected from the open air movement that would dry them out.

A good example of this is the underside of the floor mat used in my cargo van. There were no visible rips in the mat so it wasn't poured water penetration that had the sound deadening/insulation material accumulating water. It's not something that happens overnight, it's a steady but minuscule accumulation of moisture that over a decade creates the problem.

If you check the underside of a floor mat in a van that's only a couple of years old you won't notice any problems, check again when the vehicle is a decade old and you've got moisture.

 

[Optimistic Paranoid]

The semi dead air space created between the interior panels and the outer skin is in itself good insulation.  One of the simple facts that never get talked about much is that all important air space for the insulation to work properly.  The truth is that the dead air space is what IS providing the insulating quality, not the insulation they want to sell you.

Respectfully, No.  It is not.

Heat transfer occurs in one of three ways:  Conduction, Convection, and Radiation.

The space between the outer and inner walls prevents heat transfer by conduction.

To prevent heat transfer via convection, you need lots of SMALL dead airspaces, small enough to prevent air flow.  A large dead air space will have convection currents transferring the heat from one side to the other.

And of course, there is nothing to prevent heat transfer by radiation between the inner and outer walls straight across the open space.

You're right that it is the extremely small air spaces in the insulation, rather than the actual material itself that provides the insulation. But the space must be small enough to prevent air currents from occurring.

Consider a thermos bottle.  It depends on lack of contact between the inner and outer walls to prevent heat transfer by conductance.  It depends on the silver reflective surface to prevent heat transfer by radiation.  And it depends on the VACUUM between the inner and outer walls to prevent heat transfer by convection.  If the bottle leaks, and air fills the vacuum area, the thermos stops working.  Even though the "dead air space" between the inner and outer walls is much smaller than the "dead air space" between your van's inner and outer walls, it's insulation usefulness is destroyed.

I believe the "dead air space" in the van walls that you keep touting has an effective R value of exactly zero.

Regards
John

 

[highdesertranger]

good explanation OP. highdesertranger