R-value vs thermal capacity

[Juan Chacho]

I hear that vans with lots of insulation material might do well in cold weather but take hours to cool off at night in hot climates. Has anyone here experienced that, and with what insulation?

If so, I want to strike a balance between r-value and thermal capacity.

I found this article with an interesting chart: Thermal Conductivity and Specific Heat Capacity of Insulation materials at Different Mean Temperatures

 

[bullfrog !]

A lot depends on your build and the materials you use but again you are starting out with a metal box with glass windows and doors. If a high top most likely fiberglass also. You are trying to isolate the interior from the exterior while still having enough space to sleep, change clothes and maintain physical hygiene in comfortably. Any time you connect anything to the metal exterior it will conduct temperature so it becomes a concern, using aluminum strips with metal screws to hold panels for example. Opening a door, window or vent quickly equalizes the inside temperature to the outside temperature. One reason a curtain or wall is sometimes used between the driver’s front area and the back sleeping area is to reduce the effects of getting in an out of the vehicle and the large amount of glass in that area. Main reason we follow the seasons is we mainly live outside as there isn’t really enough space in a van to “live” inside for most of us and insulation or maintaining temperature in the van takes up a lot of space we need to do the other things well enough. Just my opinion stated here. I built a foam box with insulated air spaces with a entry chamber and just enough venting for two people to sleep in 7’ x 7’ x 6’ and it was still a pain to heat and cool. Main problem was keeping enough air flow to avoid condensation build up and stay alive! Lol!!! In a van insulation on the roof in the summer and on the floor in winter is important but head room for me was more important. 1/4” Luan or plywood panels with thin carpet that was easily removed and replaced worked best along with a very minimalist build worked best for me.

 

[Juan Chacho]

@bullfrog ! , have you run into the problem where, after a hot day, the insulation stays hot and makes the rig hot for hours into the night?

 

[bullfrog !]

@bullfrog ! , have you run into the problem where, after a hot day, the insulation stays hot and makes the rig hot for hours into the night?

My box is extremely less dense being foam filled interior doors covered in Poor man’s Fiberglass and has no metal fasteners and very little materials to conduct heat. If you like to experiment tape up a cheap foam cooler in a 70 degree room, take it outside and let it sit in the sun on a warm day. Poke a food thermometer into the interior and check it every hour. My box stays cool inside most of the morning as long as it stays pretty well shut up even in direct sunlight. By afternoon in 100 plus degree weather it is above 80 degrees inside. About an hour before sunset it is equal to the outside temperature. As soon as the sunsets I open vents and doors. If using my 5,000 btu AC it cools it off in less than an hour to 70 degrees. Humidity/ventilation play a role in this as well and condensation needs to be considered. By opening up things I sleep better and by midnight it is 70 degrees on the hottest days. Originally I figured no matter how well I built it it wouldn’t be air tight. I was wrong and nearly did myself in! Should have known when I couldn’t close the door when slamming it! lol!!! I installed a 14” x 14” vent and two 6” diameter floor vents which I can regulate. Even if you insulate to an extreme you will still need to heat and cool it as you will need to ventilate it to prevent condensation therefore especially if starting with a metal box it wasn’t really to me practical which is why I went to building my box. You will quickly come to the point of diminishing returns in a van in my opinion. I viewed my van as a metal tent and used a good sleeping bag with a little ventilation and carpeted panels I could easily replace to keep down condensation and followed the seasons. No sense trying to beat Mother Nature! If you do a diesel heater or propane generator and AC can easily be made high capacity enough even without insulation to do the job cheaper and better in my opinion. Full hookups if you can and it still won’t be as easy and nice as inside an apartment.

 

[INTJohn]

I hear that vans with lots of insulation material might do well in cold weather but take hours to cool off at night in hot climates. Has anyone here experienced that, and with what insulation?

If so, I want to strike a balance between r-value and thermal capacity.

I found this article with an interesting chart: Thermal Conductivity and Specific Heat Capacity of Insulation materials at Different Mean Temperatures

View attachment 37169

What climates are you going to be in?
Dude; you’re not designing an indoor amphitheater arena for 10000 people located in a 4 season city.

I think you are waaay overthinking this. I used 3M thinsulate designed & sold for vans. It’s on the expensive side as far as van insulation goes but worth it so I went with it. It’s on the sides; doors & roof.

Over the roof I put a DuraTherm ceiling liner and The floor has a Bedrug floor insulation liner covered with 3/4” plywood.

bch bum jonny

 

[Juan Chacho]

@INTJohn Hey, overthinking is a hobby of mine! There's so much conflicting information.

My climate will probably be all over the place until I get familiar with areas. Then I'll chase comfort, but with a few days a year cold (sometimes very) traveling to family for the holidays. If thinsulate and a heater is enough, that's great!

 

[LargeMarge]

...insulation material might do well in cold weather but take hours to cool off at night in hot climates. Has anyone here experienced that, and with what insulation?

If so, I want to strike a balance between r-value and thermal capacity...

.
a -- in this context, how are you defining 'thermal capacity'?
.
b -- what are you using for 'insulation material'?
In our ExpeditionVehicle, our insulation looks like this:
.. adhesive-back acoustic against the wall and ceiling, a gap, then
.. one-inch pinkboard, another air-gap, then
.. two-inch foil-side poly.
.
Choosing our habitat box, we calculated enough interior dimensions to allow about 4"/11cm of insulation and the necessary gaps to avoid thermal bridging.
.
5 -- any mass resists temperature change.
Our floor in our ExpeditionVehicle is bamboo perimeter with slate in the center.
The chunky mass of the organic stone both 17) takes longer to warm, and w) gradually radiates its blessings back into the rig.
.
Comparatively, the bamboo plank (with a lot of resin for stab- and durab-ility) is generally always cooler.
.
ï) to my tootsies, irregardless of season, carpet always feels significantly hotter.
.
№ ⁹ -- we operate a small organic teaching farm near the outskirts of Eugene Oregon.
We camp in a romantic grove, shielded from the summer sun by abundant foliage.
A couple hours prior to sundown, the rig gets opened, door and windows wide.
.
On a warm evening, we also place our Craftsman 20v adjustable fan in the entry to force the air exchange.
www.craftsman.com/products/cmce001b
After we hit the sack, the fan goes on a shelf, aimed at the bed.
.
tl;dr
.. Less mass equals more air exchange.
.. More air exchange equals less stagnation.
.
Toss in some car-camping gear, go have fun.
.
[edited to add]
Temperature control was our initial priority, then we realized we could simultaneously reduce outside noise with a third layer... adhesive-back acoustic against the walls and ceiling.
.
Our thermal bridging prevention also acts as an acoustic damper.
I hope this makes sense!

 

[rruff]

I hear that vans with lots of insulation material might do well in cold weather but take hours to cool off at night in hot climates. Has anyone here experienced that, and with what insulation?

No. This is actually in my area of expertise in my former life, so...

There is very little thermal mass is the insulation. There is way more in the stuff inside your van. If you want it to cool it off in the evening when the outside air gets cooler than the inside, open the windows and crank up your fan to draw air through.

It's silly to put too much insulation in a van, because it takes away a significant % of your space, and you need a decent amount of ventilation just for fresh air to breathe (and if you have company, getting rid of fart smells ). In other words the optimal R value for a camper wall is a lot less than a house. Ya'll who like to park in the arctic in winter, or the Hades of S AZ or S FL in summer, might want 2 inches of foam. Else you can get by fine with less... even none.

 

[rruff]

Then I'll chase comfort, but with a few days a year cold (sometimes very) traveling to family for the holidays. If thinsulate and a heater is enough, that's great!

Nothing plus nothing is enough. Seriously.

If it's a long trip that you can't do in a day, then stay north in summer or south in winter, until you get to where you can make it in one shot in one more day of driving. Or hell... just get a cheap motel. There are so many simple ways to "solve" the outlier conditions without designing your van for the extremes.

Simplicity and minimalism are important virtues in this.

I do like the 1.5" of foam I've got, but I only have that because it's the core of the sandwich structure. The insulation is a nice byproduct. When I see people adding foam and an interior wall to their van, it seems kinda silly because you could just buy a cab-chassis or cutaway, or a pickup, and build a box with the same interior wall and foam, and add an exterior wall (all bonded into a structure)... and it would be lighter with flat walls.

I don't have a heater and have slept fine in ~15F with a bag and blanket.

You are free to do whatever you like of course, and it will be cool.