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Hi everyone, Tim from Sweden here, got myself a Fiat Ducato (Promaster) and I am about to convert it. Insulation is driving me crazy though, mostly because we don't have everything thats  available to you guys as easily over here, in particular polyiso is hard to find, and very expensive. 

 The ducato is silver, so it has some reflecting properties.

The van will be used in temperatures ranging from -10 c (14F) to 35c (95F)

I will have 2 roof fans, a skylight and a stove top extraction unit. I will also have a vent/fan in the floor, to really ensure I have adequate circualtion of air, and to bring in cool air on hot days.

I will also have 2 of these 12 dehumidifiers. 

https://www.amazon.co.uk/d/Dehumidifiers/Breeze-Compact-Portable-Moisture-Kitchen-Bedroom-Caravan/B00NFRTVY6/ref=pd_sim_201_3?_encoding=UTF8&psc=1&refRID=CSB1XT4PGN1BWQD5MZN4

For heat I will be using a mr heater big buddy, thatI know ives off a bit of water vapour when burning propane. I will only be using it sparing ly, and not when I sleep, I have heavy down blankets for that.

After much deliberating, Ive landed on the following insulation sandwich, and Id like to hear your input on it before getting started.

Van Shell

Bitumen Sound deadening (1.3 mm, covering aroudn 1/3 of the area)

Polyester batting, 1 inch thick, covering everything, including the ribs. Either stuck to the shell with glue or just use doublesided mat tape, in case I want to remove it later.

https://www.slojd-detaljer.se/sortiment/...rfill-8734


Styrofoam (either EPS or XPS)  2 inches thick (1 inch for ceiling), this would be scoured and pressed against the polyester batting with:

0.16 inch pine plywwod as paneling, alternatively hardboard thats 0.11 inches.

My thinking is that the polyester will cover all the metal, so that no condensation can reach it, and then the styrofoam will be pressed against the polyester, ensuring a tight fit with no gaps.

For the floor, I was going to use the 1 inch batting to cover it all, then 0.7 inch plywood as subfloor, and a pvc floor on top. I figure the weight of the plywwood will press down the batting and fill those gaps up.

For inside the ribs, Id probably use strips of the polyester, and fill gaps with expanding foam made for wintertime.

SO what do you guys and gals think? Am I on the right track? I have heard that EPS styrofoam (white) can suck up moisture, but Im thinking with all the precautions and venting/dehumidifyers, I will be fine.
I think you have thought this through very well.

Big Grin
If EPS styrofoam "can suck up moisture", it's certainly news to me!  Styrofoam is what most flotation devices are made of.  Get a small piece and set it in a basin of water with a  brick on it for a few days, and then remove the brick and see what you find.

Your mention of fiberglass batting caused me to do some research, and I found this (2010):  "SafeTouch Polyester Batt Insulation from Dow" - https://www.buildinggreen.com/blog/safet...lation-dow

I was surprised that it had an R-value of almost 6 per inch.  But Dow is no longer making it due to lack of interest, and this article mentioned that Vita Nonwovens was producing it; but in 2013, they stopped making it, also (probably not toxic enough for American builders).  But I think it highly unlikely that polyester batting would be impermeable to water vapor.  But I am so unfamiliar with this product that I might be wrong. (It happens... occasionally)

Timoat, could you post the name of the manufacturer of the material you're considering?
Don't obsess about those gaps, dead air actually is pretty good insulation.

Make sure the paths for condensing moisture to escape at the bottom of the side panels don't get blocked.

Adding a foil-cloth reflectix "vapour barrier layer may be overkill, but it's very cheap.

Plan any under-panel electric wiring routes in advance, ideally​ accessible where any junctions are made.