any problems with thermal expansion/contraction of foam?

[Bob Hammond]

Hello,

I was reviewing some information about different types of foam panels, and I ran across a publication by DuPont. Of course, they were interested in selling a vapor barrier product (Tyvek). The gist of the article is that XPS and EPS not only pass water vapor, but more importantly they show dimensional instability of 1-4%, e.g. a 48x96 panel may shrink to 47x94 in cold temperatures assuming a 2% shrinkage, or it may expand and buckle at high ambient temperatures. Here in SE Michigan, the temp can vary from about -15F to 95F from January to July.

http://www.dupont.com/content/dam/asset ... K25107.pdf

So, has anybody seen expansion and contraction 'in real life', with unhappy consequences?

[ghcoe]

I have notice some expansion/contraction issues, but nothing that is a serious concern for me yet.

[seanc]

I haven't noticed any problems with foam expanding/contracting due to temperature. My camper has been from 10 to 110 F the last 5 months.

There were some VERY noticeable changes in wood contracting after building/parking it within sight of the ocean (WA/CA) then moving to the desert (NM).

[Don L.]

I have noticed that the roof in my camper would grow in height when it got hot. The roof has some camber to it and is about 78" wide x 11' long.
I fit my cabinets to the ceiling when it was cool (65) and when it heated up to about 90 a gap appeared where the cabinet meets the roof.
That was before I fastened it to the roof, since then I fastened the cabinet to the roof and it has stayed put. It is only a few months old at this point. My ceiling has 1/4" plywood glued to the 2" foam on the inside.

[GPW]

Most everything expands and contracts with heat and cold (admittedly at different rates) ... so we must allow for that , like when you’re hanging siding... On a Foamie , There is also another factor of “expansion” whereby small dents are “healed" by the further expansion of the compressed areas.... it’s actually quite favorable ...

Unlike Metal trailers that oilcan with the heat , Foamie trailers don’t seem so noticeable in change ... We’ve had Foamies for several years now and haven’t noticed anything unusual save the "self-healing “ ... which was totally unexpected but really Cool ..

[KCStudly]

Under construction I noticed that my roof insulation would expand in the heat and rise above my roof spars after I had sanded it all flush; not bad but noticeable to a critical eye. Then the weather would cool again and it would go back to flush. We're probably talking 1/64 inch or something like that, small.

Since I encapsulated the whole thing in FG/epoxy it is no longer an issue.

[Bob Hammond]

1/64 is probably insignificant. We're not building Chippendale reproduction furniture here!

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[KCStudly]

I agree, but if you (or anyone watching) were hopping for a nice smooth finish using PMF, be prepared to have stuff telegraph thru with temperature changes. Just saying. Alum. has oil canning, PMF has foam expansion, woodies take extra maintenance and storage, etc.

[GPW]

No Free Lunch eh !!!

[Bob Hammond]

Well, I'll find out. I just finished the cedar frame grid, and next I'll cut, fit, and glue in 1.5" foam into the grid spaces. The ambient temperature will be 88-93F.

As seen in the picture, the current weight is 251.6 lbs.

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[Bob Hammond]

The deck size is 66x105.

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[Robot]

I did get significant expansion using expanding foam (should have seen that coming.) but it was due to altitude. Built at 500ft, used at 6000ft, and they are large sections of nothing but expanding foam. I live in texas and store the trailer outside and have noticed no instability in the xps pink stuff.

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[Bob Hammond]

[quote="Robot"]I did get significant expansion using expanding foam (should have seen that coming.) but it was due to altitude. Built at 500ft, used at 6000ft, and they are large sections of nothing but expanding foam. I live in texas and store the trailer outside and have noticed no instability in the xps pink stuff.

i hadn't thought of altitude effects at all, but i don't foresee traveling to high altitudes (maybe i should!). Commercial builders must use a different type of foam that has minimal gassing characteristics.

[KCStudly]

Commercial builders must use a different type of foam that has minimal gassing characteristics.

I doubt it. Their tolerances are probably just a lot looser than ours, perhaps intentionally.

[GPW]

One might think if Outgassing was a problem , they wouldn’t package foods in foam ... but then they might ?

The wife was telling me that foam has been banned in CA ... That would be a pickle eh ?