Insulation Sandwich Question

[Jean-Louis Bourdon]

Hi

I visited a reputable company that i think will work on my van for insulation/carpeting/windows/etc.
Very pleased with what I was shown, and the answers provided to me, but still nervous on 1 point:
so before i sign with them, I'd like to check with you guys:

They are on this forum, and they posted it, so no trade secret revealed:
- "We only use the best products from Dynamat for sound deadening, closed cell foam and Dacron."

So, what do you guys think:
- does the Dacron/sandwich need to be enclosed behind a vapour barrier?
- will this combination provide me with a similar heat insulation as let's say Celotex ?
(the van will have a diesel heater if it helps answering)

thanks

 

[kn0bby]

Don’t know anything about Dacron but I’m going to put a vapour barrier in my self build.

My sandwich...

Van panel
Silent coat
Dodo Thermo van liner (foil backed dense foam)
Dodo Thermo Fleece (none moisture absorbing.
SuperFOIL SFTV Thermal, Vapour & Air Barrier.
Ply lined panels.


My only issue should be moisture behind the carpeted removable panels but I think air circulation will be sufficient at this level.

 

[Skyliner33]

There are so many opinions on this sort of stuff it get a bit mind boggling. I've seen points of view to say its better to use wool based insulation as it absorbs the moisture from the air as it cools, reducing condensation on the panels and then re releases it when the temp increases, so being better than the non moisture absorbing stuff.

 

[Steve H]

It's an interesting question.

Moisture is always present in the air and will always condense into water against cold metalwork, so the act of adding self sdhesive heavy sound deadening pads, on top of which is dense foam, insulating material etc will negate much of this condensing effect. It's debatable exactly how much WILL actually condense as no-one can say exactly, with this full coverage, and van converters want to reassure potential customers that their conversions won't actively promote rusting.

Looking logically, it certainly won't do any harm having a breathable barrier between the insulating layers and the internal panel work, but I doubt it's entirely necessary. If it were my choice, I'd probably fit it as I'm a 'belt n braces' type of character, but I doubt it's needed. If moisture laden air can get in to condense on cold metalwork, it can probably get out too..

 

[kn0bby]

There are so many opinions on this sort of stuff it get a bit mind boggling. I've seen points of view to say its better to use wool based insulation as it absorbs the moisture from the air as it cools, reducing condensation on the panels and then re releases it when the temp increases, so being better than the non moisture absorbing stuff.

The downside of that is rot, mould and damp!

 

[Vinci]

Condensation is probably one, if not the biggest issues we find in houses.....black mould anyone?…and a balance of heating and most importantly, ventilation is essential in limiting it, so any damp material in an unventilated area is risky. Holding said damp material against wood/card based panels can lead to deterioration, which is why we don’t like foam applications between rafters in roofs, and insulation quilt right in the eaves blocking ventilation and potentially holding moisture against timbers.
Realistically, how much moisture passes through the lining on short camping trips when doors are frequently opened and the van ventilated well as a result?