Trouble with foam board

[Anhedonic]

I've been building my van out and have been having a lot of trouble with getting foam board to conform to the slight curvature of the walls of my van. I've got a Promaster 2500 136WB. I tried using 1" polyiso board, cut to fit the spaces between the ribs of my van with spray adhesive but I just can't get it to stick along the curvature of the van body. I've watched countless videos and read dozens of sets of instructions but I just can't seem to get it to work. 

My only thoughts going forward are to either layer thinner layers on each other, a much more expensive prospect, or just glue up strips of the insulation along the curve of the walls. Alternately, I've considered more flexible alternatives but the soft stuff doesn't seem to have a high enough R-value by comparison or other serious downsides like weight or water absorbancy or cost. 

Does anyone have any thoughts?

 

[John61CT]

Why do you want to follow the curve?

It's called kerfing

https://goo.gl/CDZTSF

 

[bullfrog]

I believe a heat gun will allow you to bend it. Check the Foamies fourm at tnttt.

 

[John61CT]

Sorry left out the description, link is to google, filtering TNTTT.com foamie discussions on the topic.

Adjust keywords as you like.

And no, heat guns are not a great option with thick boards, kerfing is a PITA but the way to go.

But IMO likely unnecessary for this use case, unless curves are desired for aesthetic reasons.

 

[Anhedonic]

If I can't get the insulation to adhere to the van along the curvature, there will be open spaces behind it where condensation can collect. That's why I want it to conform to the curvature of the walls.

 

[Weight]

In a van, there will always be condensation. The only answer is proper ventilation. Be sure the weep holes are open at the bottom of the walls.

 

[johnny b]

20/20 hindsight which you already figured out.
For curved surfaces, (many posts on the subject), 1/2" polyiso layered is the way to go.

 

[Anhedonic]

That's kind of the way I've been leaning, Johnny B.

Weight, I have heard and read nothing of weep holes. Would you please elaborate?

 

[John61CT]

a thin layer of spray foam directly over the steel

make sure not to plug the drip holes or whatever channels the maker put in for draining water out from the inside of the panels

also seal up the gaps between sheets, corners

cover any exposed protruding metal, prevent bridging

in short, create a well sealed envelope

a good vapor barrier just under the innermost lining

Finally yes, strong controlled ventilation like a Fantastic Fan or MaxxAir is also important, don't let humidity build in the first place

 

[Anhedonic]

John61CT, these sound like good suggestions to me. Thank you.

Is spray foam a sufficient adhesive to hold the foam boards in place? I was planning for spray adhesive, probably 3M 77 or 90 and then caulking with silicone and spray foam.

Because of certain limitations, there are areas of the van (primarily the wheelchair bay in back) that I won't be able to insulate for space reasons. I'm going to close that off as much as I can from the rest of the van. A vapor barrier is probably not going to happen for this reason, but I do plan to ventilate well, both with a MaxxAir fan and an AC to bring down the humidity.

 

[John61CT]

The vapor barrier - can just be plastic dropcloth, but HD stronger is better - should seal AMAP the areas you insulate.

Prevents condensation, infiltration / convection.

Spray foam sticks like crazy, to everything, mask well.

But upside down? Long term? Dunno.

Your innermost panelling should be well secured, that holds in any loose insulation anyway.

Yes partitioning the space will help, almost always necessary when boondocking in extreme temps.

 

[DannyB1954]

The foam does not want to bend because of the covering on both sides. If you run a circular saw down the inside of the part that needs to curve, it will bend and close the kerf that the saw made. Don't saw all the way through the panel. Sometimes several cuts in the same area need to be made to make a bend. You can bend plywood in the same manor. Here is a video of what I mean If you are real picky, you can put filler in the kerfs like glue before bending.

Two layers of 1/2 inch insulation will bend easier than a 1" panel.

If I were to redo my van insulation I would build the interior wall with a gap at the top and just pour in these foam bean bag filler material that I seen at Walmart in the fabric section. Here is what I am referring to https://express.google.com/product/...ads&utm_campaign=gsx&utm_content=control_0_30 Shop around for the best price.

 

[tx2sturgis]

Sell the poly-iso boards to a home-owner or handyman who needs it, or return the unused ones to the store, and buy some regular 1/2" R-tech (single foil-faced) foam board, and double it if you need to. (Foil side inward towards the living area)

A sharp serrated kitchen steak knife will easily score and cut R-tech boards, or you can score with a utility knife. 

Regular R-tech expanded foam (white) will easily fit the curves in a van. R-value might be slightly less, but not having to cut kerfs will more than make up for that. 

And use 3M 90 spray adhesive. You may still need to use mechanical fasteners, wire, or trim to secure the foam.

 

[jonyjoe303]

how large are your sections? on mine I cut all my sections small I try to use 1x1 foot sections or smaller, glue one then glue another, by keeping the sections small it glues easier and better on curves. Installation is like a jigsaw puzzle, also its how they install heat tiles on the space shuttle. Small sections seem to stick better. For large sections you need very powerful glue and hold it with clamps till it dries completely.

I also use hotglue to install the rtech foam, it drys quickly and I never had any of the foam come loose. I think hotglue is the best adhesive for installing foam. If the glue your using keeps giving you problems hotglue gun costs 20 dollars at harbor freight, they also sell gluesticks there, you can also buy 5 pounds of gluesticks on ebay for 20 dollars, will last you years.

This is the roof of my van, its got 4 layers of 1/2" rtech foam, hotglue is the only thing holding it together, 5 years later still on there tight. And the roof does have a slight rounded curve to it. And using small sections doesnt affect the insulation as long as you cover all the bare metal. I use 4 layers because 2 inch of foam is the sweetspot where I no longer feel heat coming in from the roof.


Use something like this 15 dollar IR thermometer to find your hotspots, and add more foam, 1 layer doesnt always get you the best results. Whenever I feel hot, I break this thermometer out and point it all over my van, I usually find the heat source. Very handy.

 

[MrNoodly]

In a van, there will always be condensation. The only answer is proper ventilation.

There's another answer: stay in places with very low humidity.

 

[Weight]

Cold temperatures, mr buddy, hot breathing, will all form moisture in a closed box. even in sahara. Ventilation is still required.

 

[John61CT]

Very true, presence of mammals in the tightly enclosed space requires constant controlled venting to/from the outside, no matter what.

Exposed bare metal and/or unvented propane means the CFM exchange rate needs to be increased.

Obviously while outside conditions are comfortable, then the sealing up & insulation are superfluous, uncontrolled ventilation is fine.

 

[tx2sturgis]

Using smaller 'tiles' makes sense as posted above, (thanks for that reminder) but if you face the foil inwards, you can close all those gaps with foil tape. 

BTW there are two common temp ranges of hot glues.....I would imagine the high temp stuff would melt the foam boards where it is applied.

 

[John61CT]

But the low temp stuff will re-melt if applied directly to sunny-desert-heated skin metal.

Gorilla glue and Loctite PL-300 (PLP?) get recommended by the foamie guys.

https://vanlivingforum.com/showthread.php?tid=26363

https://www.thefoamfactory.com/accessories/adhesive.html

Another good forum here https://www.controlbooth.com/threads/best-vs-acceptable-adhesives-for-expanded-poystyrene.29664/

 

[jonyjoe303]

I use the generic gluesticks. But the gluegun itself if its too hot will melt the foam like mention above. The harbor freight gluegun I use is hot but not hot enough to melt the foam. My ryobi cordless gluegun while very convenient runs very hot, it melts the foam.

On the driver compartment I only have 1 layer of rtech foam I installed 5 years ago, the temperatures reaches up to 150 degrees in the summer. All the foam is still firmly attached. The hotglue is definitely a good adhesive for insulation and water/moisture wont affect it, I use it in building my swampcoolers, even when submerged it stays attached.

The advantage I see is no fumes, no mixing glues, and drys quickly. Thats why I do small sections, if sections are too big, one side might be drying before you finish applying all of it.

This is the gluegun I use 60 watt adtech pro100, it wont melt the foam.