Box Truck Floor Insulation

[JesseTrue]

Hello everyone!

I joined the forums a couple months ago and at that time, I was in the mindset of a solid tow vehicle and a converted cargo trailer.  I pretty much have the mechanics of insulation understood for the CCT, but I started watching the youtuber DreamSideOut.  He has converted a van-based box truck into a very nice RV.  That got me thinking again about using a box truck and towing a sturdy truck for off-road adventures/short-term camping.

Anyway, one thing that I don't quite have a grasp of is floor insulation in a box truck.  In a CCT, I would insulate on the inside, building up 1" - 1.5" over the stock floor.  Do I do the same in a box truck or should I consider insulation from below?  I just haven't seen the way that the floor is built/installed in a box truck to understand the best way.

Any advice (and warnings) about insulating and the box truck route in general would be appreaciated. I want to do the cab-attached-to-box truck built on a GMC platform because I understand that it a solid engine/transmission.  16' would be best.

Thanks!

 

[TrainChaser]

My first thought is those black rubber mats that you can get from Home Depot and farm stores like Tractor Supply. There are 3' x 5' ones for about $20 each, and 4' x 7' ones for about $30. I think the HD ones are about 1/2" thick and the horse stall mats (at places like Tractor Supply) are 3/4" (also more expensive). Lay them down and you're done. If you spill something, drag them out and hose them down.

 

[LoupGarou]

Box truck bodies I'm familiar with have a 5/4 oak floor. If the wood floor is sound without rot, consider using spray foam from underneath.

 

[JesseTrue]

TrainChaser,

Thank you. Do I need a sealant over the spray foam? Thinking the spray flexible rubber or the rhino spray?

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[firebob]

there is open cell and closed cell spray foam. I would think you would want closed cell, but i'm not sure. With closed cell there would be no need to seal it from the bottom. If you did open cell and sealed it on the bottom it would hold moisture.

 

[LoupGarou]

I would consider spraying the applied foam with black paint. After it has cured.

 

[akrvbob]

No insulation on the floor. It's a waste of time in my opinion.

 

[JesseTrue]

No insulation on the floor. It's a waste of time in my opinion.

Why is that, Bob? Van floors are typically insulated. Wouldn't coverage of small gaps between the floor boards be the minimum benefit?

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[BradKW]

I'm simply laying 4x8 sheets of rigid foam boards down with 1/4" ply + flooring...in my 16' box I have plenty of headroom to spare. I can't see any reason to mess with spray foam underneath, that could be pretty horrible. But my walls are spray foamed and that's nice.

Rick's box is only 10ft and I don't believe it has much tow capacity. He's happy with it, but I would definately get rid of the roll-up door

 

[BradKW]

Why is that, Bob? 

He's coming ffrom the angle that low-top vans are short enough on interior height as it is, and that floor insulation plays an important role in cooling (AC) not heating, and most vandwellers move location to adjust temps, not running an AC...

 

[akrvbob]

The bigger the difference between the temperature on the sides of a wall (or floor) the more force to push the warm air to the cold. Since warm air rises the floor will always be cold and little heat will be lost below the floor while maximum heat is lost through the roof. Time and money spent on the roof pays off, very little gain on the floor. A good pair of down booties solves a cold floor problem better than anything else.

 

[TrainChaser]

That is probably true in many circumstances, esp when you are snowbirding and not on the road much.

But, there can be other issues:
* COLD -- the warm air (from whatever source) does rise, but it doesn't stay there indefinitely unless it's being replaced; unless you have a heat source running even part-time, just your body temperature isn't likely to keep it warm. My first van was a cargo van (no extra windows), and it was insulated all the way around. It was pretty nice with just me and the dog, and heating food with the propane stove inside.

Some kind of insulation on the floor seems to slow down the penetration of cold from below, which affects the heat you've got stored inside. You're not going to warm up the ground below, and cold wind will blow under it. To me, it's like having a small house with three wall and the roof insulated, but the fourth wall is single-pane glass, facing north.

HEAT: Once you're parked, you're usually creating shade, so the ground (whatever material) is likely to drop to something close to the ambient air temperature. Inside, as long as you've got air moving through a vent (fan or not), it will be something close to tolerable.

BUT.... when you're driving in hot summer temps, the heat radiated by the asphalt can be tremendous. I learned this with my very first car, a Corvair (remember them?). My first car, my first job, my first paid vacation, and I headed north on I-5 from SoCal to Oregon, in summer (July or August). By the time I got to Bakersfield, I couldn't stand the heat from the floor -- my feet were on fire. I had to pull into a rest area, pull a blanket from the back seat and put it, folded, on the floor.

The first thing that someone is going to say is that a Corvair is closer to the ground than most vans. That's true, but it sure didn't make much difference when I got the big Dodge van (just metal skin all around) when I was living in Las Vegas, NV.

I wouldn't go crazy insulating the floor, I would go for simple and inexpensive (and easily removable wouldn't hurt). That's why I suggested those rubber stall mat type things. And if you're parked in the desert and misgauged how hot it was going to be, you can drag one out and put it outside the van. Also, a 1/2" isn't going to affect interior van height all that much.

 

[flying kurbmaster]

I used to think that insulating a floor was a waste of time and money until I insulated a floor on a house, it made a big difference, I am not sure on the science behind it because you would think that heat rises, but I was pleasantly surprised. I insulated my Kurbmaster under the floor which was almost a waste of time as the floor is alluminium attached to the outside walls, I haven't used enough insulation in the walls either using only 3/4 inch. I am in the process of rectifying this by adding insulatioin where I can, like the back and bottom of cupboards, I redid the ceiling and intend on redoing part of the floor. I think what Brad has done is a good solution and not that expensive, if you have the headroom, a few of sheets of insulation is not a major cost.

 

[CraigL]

The rubber mats mentioned early in the thread from TractorSupply should be avoided, as they smell and outgas HORRIBLY. I've had such outdoors for 6 mo and it/they still smell like a tire factory. Not suitable for inside a vehicle! (and probably even worse in the desert).
Be Aware.

 

[CraigL]

While I could imagine that IR reflectance FROM THE ROAD while driving might be an important heat source to avoid if possible, I have yet to see this mentioned.
My ambu box underside is "shiny", so its not a big concern--- is yours?

 

[JesseTrue]

I think I am going to insulate under the floor between any cross-braces available (haven't picked the vehicle yet) with closed cell and seal with something waterproof. This should protect from the road in the heat and from the wind in the cold.

I'll start physically looking at vans in the spring/summer to get a better idea.

Thank you to everyone who has contributed. I'll let you know how I finally build it out when that time comes.

So many great ideas and experiences to save one from bad choices.

 

[TrainChaser]

CraigL, thanks for the tip on the rubber.  None of the rubber that I've dealt with (like vehicle or kitchen floor mats) had an odor, but those large mats are meant for horses, and who cares about them?  I guess I'll have to do the 'Sniff Test' before purchasing... preferably in the sun.

"While I could imagine that IR reflectance FROM THE ROAD while driving might be an important heat source to avoid if possible, I have yet to see this mentioned.  My ambu box underside is "shiny", so its not a big concern--- is yours?"

I am thinking that IR means infrared, but acronyms are funny things.

When the ambiant air temperature is 77F, asphalt in the sun has been measured at 125F; when the air temp is 86 or 87F, asphalt can be 135 to 143F. and when the temps are 100F, asphalt can be 167F.  To think that a metal plate constantly rolling 5" to 11" above pavement that hot for a couple of hundred miles would increase the temp inside the vehicle might be assumed by some.  OTOH, since some college students can't figure out how long it takes to go 100 miles at 50 mph, maybe not.  This is an assumption on my part.

"A shiny ambu box underside..."  I can see shiny metal reflecting heat from the sun, but when placed OVER a black heat source, it sort of sounds like a frying pan.  Which is what my Corvair was when the air temp was slightly over 100F.

Drive a hundred miles on an asphalt road with your shiny box this next summer, then take off your shoes and socks and stand on the floor for a few minutes.  Post your results.

 

[DrJean]

"Insulating" the floor merely for heat might be a waste... unless you do a lot of driving (heat from the asphalt etc as mentioned) but using "insulating" product for NOISE is a must imo. Of course, I have a connected cab (Transit Van) so I do hear (or not) the noise from the cargo area.... and having 2 layers of prodex/rubber mat made a good difference. It's till a little mushy on early mornings for me, and I haven't had anything built in yet, which will require a solid base, but even putting in an Aubusson wool rug for the RTR trip was wonderful---both comfy heat wise and muffler.

 

[StarDestroyer]

I'm currently working out insulation for my cargo van. From what I've read and understand, insulating solely for heat (as mentioned in here, even) can potentially be a waste. Not familiar with the rubber mats, personally, but I do know that I'll have limited headroom as it is, so something like rubber mats isn't preferable in *my* situation, at least. After doing some research, I'm considering going with Peel & Seal aluminum roll flashing. You can get it at Lowe's for about $1.30 per square foot. Not sure if this is the best choice, but for someone primarily concerned with sound deadening without risking too much space, this seems like a good deal to me...

https://www.lowes.com/pd/Peel-Seal-...s-6-in-x-25-ft-Aluminum-Roll-Flashing/1018733

 

[DrJean]

I'm not familiar with the peel and seal. Things to think about are if you put a metallic surface against a metallic surface it will conduct the temperature you might be trying to avoid. I've read that this material is not made for vertical installation.... I think you might be right about sound deadening... are you putting this under the floor, or as the floor layer?

As for heat "insulation" let me share that having the prodex on the walls and ceiling, and in the windows was HUGE for keeping the van warmer at the RTR! I did not do the rear doors and slider since they came with the inserts already (and I was time limited) and cold air came right through them.