Lets talk about rigid foam insulation


I am installing the foam board from Home depot/lows. it only has foil on one side and a plastic type film on the other. my upper topper part is where its going. some on the metal area.
then when I get the funds I will add the Jute stuff that has foil on one side to the lower part of the van cause its mends better to the curves and such.
hope it performs as well as I hope for some winter camping.

mine is a work in progress as I need funds for the goods. plus its winter time and hard to glue in cold weather. last week we didn't get above zero.


I like the idea of the radiant shield, and the additional R-value of the Polyisocyanurate, but it has its drawbacks.

Foil face on both sides

Cellular reception within camper will suffer greatly

That's not a drawback! That's end of the world EMP protection! :wings:


Believe it or not, while EMP protection was not a thought, infrared imaging has been...

A camper lined with a metallic radiant shield would do pretty good as far as shielding it from infrared imaging:ylsmoke:


New member
i work in the building science industry, i would go with XPS. Polyiso has been found to lose r value at colder temps. It's something to do with the blowing agent of the foam actually contracts as it gets colder therefore decreasing r value. As far as adhesion and sealing, i would recommend vulkem, it is a very flexible and very stick polyurethane sealant you can get at home depot. My boss has two pieces of xps that are joined by vulkem and are still flexible... after 20 years. The only drawback to vulkem is it STINKS while off-gassing.


New member
oh, one bonus for r-max, if you get the stuff that is branded "r-max"(i believe a dow product) it is fire rated. and can be left exposed in building situations.


Expedition Leader
i'm very surprised this thread lasted as short as it is/ did.

is there another thread which has become Foamipedia? I don't think insulation can be isolated not to include vapor barriers and ventilation.


I plan to use rigid foam and would like to know more as well. This is a great thread.

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For the record, I'm 100% sold on XPS

We built our custom camper a bit more than 4 years ago now.
And have spent nearly a month in it, every year since building it.
Loading it up again tomorrow evening for another trip :ylsmoke:

It has performed flawlessly, all the way down to -20 or so, so far.
When considering R-value, strength, and weight, Id argue that XPS is as good as it gets.

Excellent R-value, rigid, and lightweight


Also, this is a great link that discusses the typical rigid foam options.



Expedition Leader
have you noticed any signs of condensation? a month at a time without any would seem like a good testament to your construction materials & methods. did you add a vapor barrier (which side of the insulation) and/ or vent each bay for air circulation?

like the refrigerator light going out when the door is closed, I continue to wonder what goes on inside the wall after the inner surface is installed.

(the provided link wants me to be a "prime" member)


With the construction methods used, there is no need for additional vapor barriers.

Prior to insulating the entire interior of the marine plywood skins as well as the VG fir framing, is 100% encapsulated in epoxy.
Then the foam is installed, tight fit, bonded to framing and the interior of the skins.
Then a layer of 3mm luan ply is used for an interior skin. Again, being bonded to the foam and framing.

It is essentially built like a hell-for-stout ice chest. And condensation that is produced will form on the windows, and frames.

With respect to accumulated condensation, there really isn't any way to 100% avoid it. Minimize it, yes, but you will never completely avoid it (with a passive system).

The only time we have more than a little bit of condensation is during the winter, when we use the camper as a ski lodge. We camp out for weeks at a time sometimes at ski resorts.
Only then do we have to address condensation as a "problem". The roof hatch collects enough that it will drip, and the aluminum frames on the dual pane insulated windows will sweat, and frost.

Best I can figure is that the added moisture being tracked in on boots, clothes, and gear push the moisture level to the point of it being an issue.
It still isnt bad though. Nothing a hand towel wont fix. I did add a roof vent a few years ago to address this issue, and it has helped a great deal.
It does effect the overall efficiency of the heating system though, as you are allowing hot air out, and drawing cold air in (from somewhere).

A non-passive method would be a dehumidifier, which would work great. But so far, it simply isn't enough to worry about.
If we were full-timing it, Id consider it. But for a few weeks or months at a time, I dont see the payoff.

When camping even in zub zero conditions, but not on a ski trip, condensation is never an issue.
The window frames will sweat a bit and frost, but there is never enough moisture to even wipe down.



I love how your camper turned out.

What adhesive did you use to glue the foam to the walls?

Did you use regular boat style epoxy to seal the wood with fiberglass cloth on it?

I definitely like how everything turned out.

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The prototype used LOTS of PL Premium.
This includes bonding the foam to the structure.

Epoxy used is a marine epoxy. Although when using marine ply you can get away without any fiberglass cloth.
Lower grade plywoods tend to "check" which will crack the paint. Marine ply does not check.


As a prototype I felt like it was a good way to test the theory, so we went without glass. So far so good.

All that said, Im currently testing monstaliner and will more than likely coat the entire thing with it. :ylsmoke:

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