Gaps from rib depth

[user 29503]

I have a 1995 Chevy G10.  I want to put 1" Polyiso-type insulation on the walls.  Towards the top of my ribs (near the ceiling), the foam will fit very nicely in the little rut/canal, whatever you want to call it.  Toward the bottom the rib deepens to 1 3/4", potentially leaving a 3/4" of gap from the 1" foam already in place to the lip of the rib (where the paneling is potentially going to be screwed to).  This "deepened" area of the rib is about a foot and a half to two feet in height from the floor of the van.  My questions are:

Does this 1" gap between the foam and paneling need to be filled with insulation? Or, is it overkill and the gap will be fine?

If I didn't want to put insulation there, could I fill the gap with storage space for something small?

Thanks van people,
Rabbit

 

[Camper]

I used Polyiso in my Chevy van and filled all the space's as best I could. But, it's your van and insulate it as you see fit.

 

[BelgianPup]

Check out the Humble Road videos. He's a guy who know what he's doing and can actually think things through. I'm sure that I saw one of his videos where he leaves those gaps open so moisture isn't trapped under the floor.

 

[MrNoodly]

Space between insulation and the surface material (interior or exterior) can act as insulation. In the case of conductive thermal transfer, the gap is like the space between your hand and a hot surface, compared to your hand on the hot surface. In the case of convective thermal transfer, the gap (if sealed) is a pocket of still, no-draft air, like the space inside double-pane windows. In the case of radiant thermal transfer, the gap slows transmission because there are fewer molecules in air to transmit the thermal difference (like the hand example above). And if there's a shiny surface, it can reflect the heat back.

So don't worry about the gap. It wouldn't hurt to fill it, but it wouldn't hurt to leave it.

Besides, no matter how much insulation you use, heat and cold will find their way in and out of the van via the heater/AC vents, a vent that balances internal and external air pressure, and the gaps around doors (particularly in 25 year old vehicles with aging hinges and rubber seals). You do what you can, then adapt to the conditions in other ways.

 

[user 29503]

Thank Mr. Noodly.  My apologies for the delay, I must not have checked "Receive email notification of new replies".  I have one more question.  I bought blue foam insulation board from Lowes.  It has plastic backing on either side for, I'm assuming, a vapor barrier.  Do I want to remove that plastic and glue the bare foam on the van wall?
The reasons I ask are: I've heard some negative things about moisture barriers, that they provide a seal for moisture rather than avoiding it  I'm unaware if foam can actually mold.
Second reason I ask is I hypothesize that when I apply the 3M adhesive, it's not actually the foam adhering to the wall, but the plastic barrier.  And as I cut (neatly I might add, with a very sharp, long blade), it tends to still loosen that plastic, so I fear integrity issues once it's glued.
Thanks again,
Rabbit

 

[user 29503]

Check out the Humble Road videos.  He's a guy who know what he's doing and can actually think things through.  I'm sure that I saw one of his videos where he leaves those gaps open so moisture isn't trapped under the floor.

Thank you I will.

 

[MrNoodly]

...I bought blue foam insulation board from Lowes.  It has plastic backing on either side for, I'm assuming, a vapor barrier.  Do I want to remove that plastic and glue the bare foam on the van wall?

I don't have any experience with that type of foam board. The pink Owens-Corning foam board I used didn't have it. And I taped mine in place rather than gluing, because I got tired of holding the board in place while the glue set up.

 

[islanderxx]

I have a 1995 Chevy G10. I want to put 1" Polyiso-type insulation on the walls. Towards the top of my ribs (near the ceiling), the foam will fit very nicely in the little rut/canal, whatever you want to call it. Toward the bottom the rib deepens to 1 3/4", potentially leaving a 3/4" of gap from the 1" foam already in place to the lip of the rib (where the paneling is potentially going to be screwed to). This "deepened" area of the rib is about a foot and a half to two feet in height from the floor of the van. My questions are:

Does this 1" gap between the foam and paneling need to be filled with insulation? Or, is it overkill and the gap will be fine?

If I didn't want to put insulation there, could I fill the gap with storage space for something small?

Thanks van people,
Rabbit

You can't overkill the insulation on R-value if the cost is minimal. What is important is to reduce vacant air space as much as possible. The interior surface of the living space should be sealed from the space between the interior walls and the exterior surface of the van to reduce convection.