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Hey, thanks!
I've used "Jackofoam 300" from Jackon (maybe its a different name over here..), but it looks to be the same product. I've read that XPS performs a lot better than other products like polyiso in cold temperatures, so thats why I chose XPS. I'll consider Polyiso for walls / ceiling though, and I'm planning on using Armaflex in the hard to reach spaces (and oddly shaped parts like the wheel wells).

Yes, the battens are pressure treated. I thought that would be better for mold protection, but then again, I don't know these this very well, so my very simple logic thought PT must be the way to go, since the price was almost the same anyway. I did not think of any reaction with fasteners to be honest..hmm. I'm anyway planning to fasten them with Sikaflex, not making any holes in the floor (I'm keeping the bulkhead, so I have that extra protection anyway in case of an accident).

As for the battens, the idea was to have a solid base to mount the interior into. I've also seen every other youtuber do this, so I guess I did not think of leaving them out.
I use XPS high load on the floor of my vans without battens. I use XPS high load not for the psi rating but for the water impermeability. Polyiso can absorb liquid water and when it does & when under “load” it can turn to mush.

The only drawback using XPS under your floor is the ability for that insulation to telegraph noise “squeaks”. It is simply less “squeak resistant” than polyiso.

Roof & Walls; I use polyiso as IMO there is less likely chance of polyiso absorbing liquid water. In my 2021 build I will use foil face & aluminum foil tape the raw edges. Walls & Floors in direct sun & in hot climates can really heat up (also depends on your van colour & roof mounted solar panels). Polyiso performs much better than XPS for high temp heat. Polyiso performance drops off at the opposite spectrum “extreme cold”. For the climate my van will “live” it makes sense to use polyiso in walls & roof. YMMV.

Regarding “seeing others on Youtube”; I understand the human nature. You have stumbled upon & become a Forum Member. I have a bias towards “The Forum”. IMO for Promaster(ish) van builds this Forum” is “The Place To Be”. I post a lot of “crap” on here & some of it might even be right. This is the only van forum I am on (actually it is really the only forum I visit). I think it is a good idea to look at Youtube for ideas, but I think it is very prudent to vet those ideas here. There are many experienced science based DIYer Members here & a mountain of knowledge, albeit sometimes contradictory but that is the great thing about this forum it is a wonderful venue to share opinions & back them up with Science & Logic (rather than emotion).

You can use your build thread here to your advantage (if you wish), but posting questions on your intended design prior to building & obtaining opinions/ideas to assist you in your design. You are Design/Building a DIY van 1st time? It ain’t the building that is hard (exception back aches), but the Design.

The Forum Membership has a wide spectrum of; Architects, Engineers, Scientists, Construction Types, Mechanics, & Much More - Most willing to help you out. All ya gotta do is ask 😁👍

I have a 2021 build thread started months ago (van #2) - I ask for advice on it. Wish I was a member when I built my 2018 as it would have saved me some errors & 💸💸💸.
 

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Some “light” reading for you if you have an interest in insulation (one of the worse misunderstood DIY van build topics there is on the internet in my opinion);



@GaryBIS insulation tests;



My reference to polyiso absorption (do not get fooled by the foil-face that is rarely sealed & easily punctured real world) look & the raw polyiso.
 

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Discussion Starter · #24 ·
I use XPS high load on the floor of my vans without battens. I use EXP high load not for the psi rating but for the water impermeability. Polyiso can absorb liquid water and when it does & when under “load” it can turn to mush.

The only drawback using XPS under your floor is the ability for that insulation to telegraph noise “squeaks”. It is simply less “squeak resistant” than polyiso.
Yep, I've already noticed the squeaks. I've made sure to cut away material along the sides against the van skin, and will be using expanding foam to fill the gaps. Hopefully that will make it squeak free. That would indeed annoy me a lot.

Roof & Walls; I use polyiso as IMO there is less likely chance of polyiso absorbing liquid water. In my 2021 build I will use foil face & aluminum foil tape the raw edges. Walls & Floors in direct sun & in hot climates can really heat up (also depends on your van colour & roof mounted solar panels). Polyiso performs much better than XPS for high temp heat. Polyiso performance drops off at the opposite spectrum “extreme cold”. For the climate my van will “live” it makes sense to use polyiso in walls & roof. YMMV.
Aha, I was under the impression that polyiso also was water impermeable, but its only the aluminium coating that keeps it from being a sponge? Like, for some of the uneven surfaces I initially planned to "cut into" the polyiso block to make it fit (some "bumps" in the van skin, like the lower panels), but then thats a bad idea I guess (unless I tape it). Another use would be to "drill holes" to make it fit over the plastic clips holding the rocker panels in place. The aluminium surface also acts as a reflective surface (with an airgap) i suppose, unlike XPS as an alternative for the walls & ceiling too, so there is that upside too.


Regarding “seeing others on Youtube”; I understand the human nature. You have stumbled upon & become a Forum Member. I have a bias towards “The Forum”. IMO for Promaster(ish) van builds this Forum” is “The Place To Be”. I post a lot of “crap” on here & some of it might even be right. This is the only van forum I am on (actually it is really the only forum I visit). I think it is a good idea to look at Youtube for ideas, but I think it is very prudent to vet those ideas here. There are many experienced science based DIYer Members here & a mountain of knowledge, albeit sometimes contradictory but that is the great thing about this forum it is a wonderful venue to share opinions & back them up with Science & Logic (rather than emotion).
As I am starting out without any prior skills or experience, we all have to find inspiration somewhere I guess :) I've used countless hours on youtube and van conversion blogs and articles, some good, and others not so much. As always, I try to keep an open mind, and figure out what information is reliable and what would work for me or not. I've looked at this forum a lot too, and I have to say, its a very active and welcoming forum. It will soon be on my top list I guess :)

Lol, before I started this project, the only car related stuff I had ever done was changing a windshield wiper. Set the bar high and dream big right? :) I am however an engineer (although a software developer) so I'm at the very least used to technical stuff and not afraid of using Google to figure stuff out :)

You can use your build thread here to your advantage (if you wish), but posting questions on your intended design prior to building & obtaining opinions/ideas to assist you in your design. You are Design/Building a DIY van 1st time? It ain’t the building that is hard (exception back aches), but the Design.

The Forum Membership has a wide spectrum of; Architects, Engineers, Scientists, Construction Types, Mechanics, & Much More - Most willing to help you out. All ya gotta do is ask 😁👍
Thank you so much. I will probably do a little bit of both as the project progress. I don't have anyone else to throw ideas and questions at, so I love a helping community :)


Some “light” reading for you if you have an interest in insulation (one of the worse misunderstood DIY van build topics there is on the internet in my opinion);



@GaryBIS insulation tests;



My reference to polyiso absorption (do not get fooled by the foil-face that is rarely sealed & easily punctured real world) look & the raw polyiso.
Yes, the more I read about insulation, the more confused I get :D Its a never ending topic it seems :) I've gone through youtube and countless van conversion blogs and articles. I don't like to make uninformed or wrong hasty decisions, so I take my time doing research, but even then, its possible to get it wrong I guess :)

When it comes to insulation, which are all my next steps, my current plan is as follows:
  • Floor - XPS 50mm. I plan to adhere it with expanding foam.
    • Also expanding foam in all the cracks and smaller areas not covered by the XPS panels.
    • Aluminium foil tape over the battens to complete the "vapor barrier" as the battens are the only thing not water impermeable (although, if the battens get wet I probably have some more serious issues at hand).
  • Walls - Polyiso 50mm. I plan to adhere it with a non expandable fixing foam, like Sika FoamFix.
    • Expanding foam around the edges.
  • Ceiling - Polyiso 50mm. Same procedure as for the walls (and leaving a small airgap for the panels).
  • Inside the "ribs" (or whatever they are called?) I'll use either expanding foam or some sort of mineral wool (or a mix between the two depending on the space).
    • Some parts needs to be accessible after installation, like access to the brake lights, etc.
  • Cover all bare metal and ribs with a "reflectix" type of material to close any thermal bridges and prevent moist air from condensing on the cold van skin.
  • For the headspace above the drivers cab, inside the doors and wheel arches I'll use Armaflex. Its very flexible, has the same thermal properties as polyiso and also water impermeable. Only downside is it's only 25mm (1") thick, and slightly more expensive.
    • Maybe I'll add some mineral wool too some hard to reach places. After all, the doors have drain holes, so I'm less worried about moisture buildup inside the doors than other places.
In general, I'd like to use as much water impermeable material as possible, and not base everything on a vapor barrier, thats one way or the other, is going to fail at a point. Water will find its way no matter what I guess :)

I've also looked at thinsulate, which people seem really happy about, but its near impossible for me to source it, as no one sells it in my parts of the world. International orders get really expensive fast, so I've put away the idea of using Thinsulate.
 

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Yep, I've already noticed the squeaks. I've made sure to cut away material along the sides against the van skin, and will be using expanding foam to fill the gaps. Hopefully that will make it squeak free. That would indeed annoy me a lot.



Aha, I was under the impression that polyiso also was water impermeable, but its only the aluminium coating that keeps it from being a sponge? Like, for some of the uneven surfaces I initially planned to "cut into" the polyiso block to make it fit (some "bumps" in the van skin, like the lower panels), but then thats a bad idea I guess (unless I tape it). Another use would be to "drill holes" to make it fit over the plastic clips holding the rocker panels in place. The aluminium surface also acts as a reflective surface (with an airgap) i suppose, unlike XPS as an alternative for the walls & ceiling too, so there is that upside too.




As I am starting out without any prior skills or experience, we all have to find inspiration somewhere I guess :) I've used countless hours on youtube and van conversion blogs and articles, some good, and others not so much. As always, I try to keep an open mind, and figure out what information is reliable and what would work for me or not. I've looked at this forum a lot too, and I have to say, its a very active and welcoming forum. It will soon be on my top list I guess :)

Lol, before I started this project, the only car related stuff I had ever done was changing a windshield wiper. Set the bar high and dream big right? :) I am however an engineer (although a software developer) so I'm at the very least used to technical stuff and not afraid of using Google to figure stuff out :)


Thank you so much. I will probably do a little bit of both as the project progress. I don't have anyone else to throw ideas and questions at, so I love a helping community :)




Yes, the more I read about insulation, the more confused I get :D Its a never ending topic it seems :) I've gone through youtube and countless van conversion blogs and articles. I don't like to make uninformed or wrong hasty decisions, so I take my time doing research, but even then, its possible to get it wrong I guess :)

When it comes to insulation, which are all my next steps, my current plan is as follows:
  • Floor - XPS 50mm. I plan to adhere it with expanding foam.
    • Also expanding foam in all the cracks and smaller areas not covered by the XPS panels.
    • Aluminium foil tape over the battens to complete the "vapor barrier" as the battens are the only thing not water impermeable (although, if the battens get wet I probably have some more serious issues at hand).
  • Walls - Polyiso 50mm. I plan to adhere it with a non expandable fixing foam, like Sika FoamFix.
    • Expanding foam around the edges.
  • Ceiling - Polyiso 50mm. Same procedure as for the walls (and leaving a small airgap for the panels).
  • Inside the "ribs" (or whatever they are called?) I'll use either expanding foam or some sort of mineral wool (or a mix between the two depending on the space).
    • Some parts needs to be accessible after installation, like access to the brake lights, etc.
  • Cover all bare metal and ribs with a "reflectix" type of material to close any thermal bridges and prevent moist air from condensing on the cold van skin.
  • For the headspace above the drivers cab, inside the doors and wheel arches I'll use Armaflex. Its very flexible, has the same thermal properties as polyiso and also water impermeable. Only downside is it's only 25mm (1") thick, and slightly more expensive.
    • Maybe I'll add some mineral wool too some hard to reach places. After all, the doors have drain holes, so I'm less worried about moisture buildup inside the doors than other places.
In general, I'd like to use as much water impermeable material as possible, and not base everything on a vapor barrier, thats one way or the other, is going to fail at a point. Water will find its way no matter what I guess :)

I've also looked at thinsulate, which people seem really happy about, but its near impossible for me to source it, as no one sells it in my parts of the world. International orders get really expensive fast, so I've put away the idea of using Thinsulate.
I think most of your insulation plan is good. Here is what I believe;

First; The only real way to deal with the multiple "Vapour Barrier" issue is to do a "Total Spray Foam Job" It is my opinion that this "kinda" makes the van metal skin and the spray foam one "almost" monolithic thick vapour barrier. This "kinda" solves "the vapour barrier issue". I almost did this in Van #1 but opted for what I think is the next best thing if not a "Total Spray Job" which is XPS on floor & Polyiso on walls and ceiling and Great Stuff Door & Window spray to fill in other areas. There are other reasons why I did not choose a "Total Spray Foam".
Liquid Material property Gas Cylinder Packaging and labeling


For me, I would not use in a van; Denim, wool, fiberglass, mineral wool (I did experiment with this but took it out and used polyiso), Thinsulate, Lizard Skin (but I have had Oxtail Soup)🤫.

Plywood is typically a vapour barrier (especially if sealed or exterior grade).

If the design can incorporate a small amount of insulation on the warm side for any thermal breaks - great, If not a "sill gasket" on the warm side even helps (maybe more than stringing thinsulate into the cold side of the ribs etc). The Ribs in the PM are about 1" off the van metal roof, so if you have more had room to start and can give up another 1/2" in head clearance 1" between the roof ribs and 1/2" over the roof ribs would at least get you some R Value on the warm side of the thermal bridging roof ribs. This is what I consider a high cost vs little gain item, but I thought I would mention it.

Be aware of the major thermal loss areas of your build & have a plan on how you are going to deal with that. Uninsulated Cab with huge areas of glass, Thermal bridges such as rear doors and slider door, Windows are all massive thermal loss areas. @GaryBIS has a pretty good thermal loss calculator on his build site. You would have to configure it to your Van, but it will get you there to understand what your thermal losses might be & what size furnace you might need.

At the end of the day my perspective on "Van Envelope" is it will not be perfect, & I will just do a reasonable job and attempt to reduce/eliminate mould food, be conscience of the moisture I introduce into the van with my use "cooking etc", as my main goal is to be comfortable and to not grow mould. So I will do what I feel is a practical best practice within reason.
 

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XPS vs Polyiso & "Foil Face Polyiso"

Rectangle Slope Font Parallel Plot


XPS is direct buried against foundations with soils - They do not do that with Polyiso

Here is a temp R Value XPS wins out on Polyiso in the cold - but not in the heat - If you plan on being in warm areas the roof and walls can get quite hot & especially if you have a dark van paint job.

Font Rectangle Material property Screenshot Parallel






Here is more on the XPS vs Polyiso if you care to read the attached file pdf.
 

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Discussion Starter · #27 ·
I think most of your insulation plan is good. Here is what I believe;

First; The only real way to deal with the multiple "Vapour Barrier" issue is to do a "Total Spray Foam Job" It is my opinion that this "kinda" makes the van metal skin and the spray foam one "almost" monolithic thick vapour barrier. This "kinda" solves "the vapour barrier issue". I almost did this in Van #1 but opted for what I think is the next best thing if not a "Total Spray Job" which is XPS on floor & Polyiso on walls and ceiling and Great Stuff Door & Window spray to fill in other areas. There are other reasons why I did not choose a "Total Spray Foam".


For me, I would not use in a van; Denim, wool, fiberglass, mineral wool (I did experiment with this but took it out and used polyiso), Thinsulate, Lizard Skin (but I have had Oxtail Soup)🤫.

Plywood is typically a vapour barrier (especially if sealed or exterior grade).

If the design can incorporate a small amount of insulation on the warm side for any thermal breaks - great, If not a "sill gasket" on the warm side even helps (maybe more than stringing thinsulate into the cold side of the ribs etc). The Ribs in the PM are about 1" off the van metal roof, so if you have more had room to start and can give up another 1/2" in head clearance 1" between the roof ribs and 1/2" over the roof ribs would at least get you some R Value on the warm side of the thermal bridging roof ribs. This is what I consider a high cost vs little gain item, but I thought I would mention it.

Be aware of the major thermal loss areas of your build & have a plan on how you are going to deal with that. Uninsulated Cab with huge areas of glass, Thermal bridges such as rear doors and slider door, Windows are all massive thermal loss areas. @GaryBIS has a pretty good thermal loss calculator on his build site. You would have to configure it to your Van, but it will get you there to understand what your thermal losses might be & what size furnace you might need.

At the end of the day my perspective on "Van Envelope" is it will not be perfect, & I will just do a reasonable job and attempt to reduce/eliminate mould food, be conscience of the moisture I introduce into the van with my use "cooking etc", as my main goal is to be comfortable and to not grow mould. So I will do what I feel is a practical best practice within reason.
Thank you for the detailed and insightful reply. May I ask why it is that you don't recommend any of the mineral wool of fabric types of material? Is it due to the fact that it will be "sandwiched" in between two vapor barriers, effectively?
For example, unlike to roof ribs (which are quite small), the side ribs in the walls are quite big, and would leave a huge heat bridge if untreated. I will run conduit and cables through, but some are big enough to consider other types of "filler" material than spray foam I guess. Or at least, I am considering it.

So, I'm still in the process of figuring out the best way to insulate ribs and doors properly. Another idea I've had is to use mineral wool in the doors and not a vapor barrier in front, just cladding, so that the material can "breathe".

For the roof ribs, I need extra space for the insulation (50mm) so my idea was to attach battens on top for easy installation of the roof.

Obviously, for the really big thermal routes like windows, I will have to construct a cover I can place on top to stop all the heat from escaping. I have one big side window, and two at the back doors, so they have to be covered during the night unless I want to freeze to death :)

As for the foam, I am also not able to source "great stuff", which annoys me quite a bit. I live in the part of the world where shipping costs from Amazon usually are 2x the price of the product :D I know, its a first-world problem, but still.. I've done quite a bit of research into the "can" types of foam I am able to get hold of, and the best one I've found so far is PUR from Tec7 with a water absorption rate of 1% volume (https://tec7.com/storage/files/7d5b...6b42/purnovatechtecv2020-03-05-09-42-36en.pdf). Most other foam products have a lower rate of closed cells, and well, act more as a sponge I guess.


XPS vs Polyiso & "Foil Face Polyiso"

View attachment 79722

XPS is direct buried against foundations with soils - They do not do that with Polyiso

Here is a temp R Value XPS wins out on Polyiso in the cold - but not in the heat - If you plan on being in warm areas the roof and walls can get quite hot & especially if you have a dark van paint job.

View attachment 79724





Here is more on the XPS vs Polyiso if you care to read the attached file pdf.
Thanks for the reading material. I think, the PDF you linked me, I've read through it before, and thats the one that got me on the idea of using XPS over alternatives like polyiso. Also, as I can see from the table, XPS still performs fairly well in high temperature, although not as good as polyiso, so I am also considering using XPS in the whole van.
 

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Hi,
I would not use XPS in walls or ceiling because the max service temp is 165F and these areas could see temps in this area on rare occasions. DuPont (or DOW?) have lots of cautions on their website about keeping XPS from getting to hot - like don't leave it outside in the sun with the black lettering facing the sun - its not a fictional problem. As RV points out XPS is great for the floor, which won't see high temps.

On the insulation test I did under quite humid conditions the Polyiso did not pick up any water weight (sample weighed before and after to within a gram). So, XPS is no doubt better on moisture resistance, but Polyiso is probably good enough? People use Thinsulate and Wool, which are very permeable to water vapor, and I've not heard any horror stories from them about moisture problems.

The R value per inch of Poliso does go down with temperature, but it starts quite a bit higher than XPS and the crossover point where the Polyiso R value drops to the same value as XPS is quite low - about -10F outside temp. There are test data on the Building Science site on R value of Polyiso vs temperature. Its important when looking at this data to remember that the temperatures in the plots are the mean temperature of the insulation, so, if the outside temp is 0F and inside temp is 60F, the mean temp is 30F (not 0F). Even at lower -10F temps, the R value of Polyiso does not plummet, it just gets a bit lower than XPS.

Gary
 

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Discussion Starter · #29 ·
Hi,
I would not use XPS in walls or ceiling because the max service temp is 165F and these areas could see temps in this area on rare occasions. DuPont (or DOW?) have lots of cautions on their website about keeping XPS from getting to hot - like don't leave it outside in the sun with the black lettering facing the sun - its not a fictional problem. As RV points out XPS is great for the floor, which won't see high temps.

On the insulation test I did under quite humid conditions the Polyiso did not pick up any water weight (sample weighed before and after to within a gram). So, XPS is no doubt better on moisture resistance, but Polyiso is probably good enough? People use Thinsulate and Wool, which are very permeable to water vapor, and I've not heard any horror stories from them about moisture problems.

The R value per inch of Poliso does go down with temperature, but it starts quite a bit higher than XPS and the crossover point where the Polyiso R value drops to the same value as XPS is quite low - about -10F outside temp. There are test data on the Building Science site on R value of Polyiso vs temperature. Its important when looking at this data to remember that the temperatures in the plots are the mean temperature of the insulation, so, if the outside temp is 0F and inside temp is 60F, the mean temp is 30F (not 0F). Even at lower -10F temps, the R value of Polyiso does not plummet, it just gets a bit lower than XPS.

Gary
Thanks Gary, thats a fair point I missed in the process too. I've read many of the articles you have made on your website, keep up the good work! Its really helpful for newbies like me :)

I think I'll stick to my original plan then, polyiso and foam it is. I'm trying to make the van work in both cold and hot climates, but I guess thats a hard nut to crack. I was initially planning of filling every rib with expanding foam too, but I think I will use more mineral wool type of material, in case I need to pull som cables or take anything out at any point.

Another point on insulation I've not seen anyone cover in great detail yet, is the health side of it. I mean, I am going to live in the van full time for a year at least, so I'de like to live in a healthy environment, if thats even an issue. I guess some materials are better than others. Like, most expanding foams are very toxic until cured (at least according to the safety data sheets), but unsure about the long-term effect of relying too much on that sort of material?
 

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Hi,
I did not do a lot of filling of the ribs/frames, but I did work with Thinsulate a bit on filling the ribs, and its pretty nice for that. You can use a flexible wire to hook the scrim cloth on the back of the Thinsulate and pull it up into the rib that way. Probably other insulations with a scrim that would also work.

Gary
 

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Discussion Starter · #31 ·
Hi,
I did not do a lot of filling of the ribs/frames, but I did work with Thinsulate a bit on filling the ribs, and its pretty nice for that. You can use a flexible wire to hook the scrim cloth on the back of the Thinsulate and pull it up into the rib that way. Probably other insulations with a scrim that would also work.

Gary
I cannot source thinsulate from anywhere in my parts of the world, so I have to rely on other types of material. But I'm sure I'll find something I can stuff in there :)
 

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XPS vs Polyiso & "Foil Face Polyiso"

View attachment 79722

XPS is direct buried against foundations with soils - They do not do that with Polyiso

Here is a temp R Value XPS wins out on Polyiso in the cold - but not in the heat - If you plan on being in warm areas the roof and walls can get quite hot & especially if you have a dark van paint job.

View attachment 79724





Here is more on the XPS vs Polyiso if you care to read the attached file pdf.
Hi RV,
I think its important when looking at the table that shows polyiso R values at different temps is that the 15F is the mean temp of the insulation. If the inside temp is (say) 60F, and the mean temp 15F, then the outside temp is -30F -- pretty chilly :) But, Foresty Forest did do -40F once, so not totally unreal :)
My reading of the test data on the Building Science site is that XPS and Polyiso have the same R value at about -10F outside with an inside temp of 60F.

Gary
 

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I cannot source thinsulate from anywhere in my parts of the world, so I have to rely on other types of material. But I'm sure I'll find something I can stuff in there :)
I used poly-iso for the floor, walls, and ceiling. On the walls and ceiling, it is glued in place and edge-sealed with a non-expanding spray foam (GreatStuff Doors and Windows).

In the doors and channels, I used a polyester batting product called Tyvek Thermawrap. It may not be available in your area, but it shows there are alternatives to Thinsulate. You want a material, like polyester, that is hydrophobic and will not compress or migrate over time from the vibration of driving. This is especially important when insulating inside doors that get slammed all the time. A spray contact-cement will help hold it in place.

@GaryBIS and others have also questioned the benefit of insulating small channels (roof ribs, etc). It is probably insignificant compared to the thermal bridging of the surrounding metal. It is probably better to focus on insulating the outside of those channels. However, thermal bridging is still evident on the bigger channels that I insulated inside. In cold weather, I see condensation on those exposed metal surfaces.
 

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Thank you for the detailed and insightful reply. May I ask why it is that you don't recommend any of the mineral wool of fabric types of material? Is it due to the fact that it will be "sandwiched" in between two vapor barriers, effectively?
Many reasons - But primarily due to the air transfer (think moist air & look at @GaryBIS tests). Hydrophobic or not dew can collect when air reaches the dew point. Also even Nasty Asbestos is safe when incapsulated 😳 - Whatever you believe in regards to friable “fiber shedding materials” fiberglass & mineral wool are at best uncomfortable to breath & @ worst cause health issues.


For example, unlike to roof ribs (which are quite small), the side ribs in the walls are quite big, and would leave a huge heat bridge if untreated. I will run conduit and cables through, but some are big enough to consider other types of "filler" material than spray foam I guess. Or at least, I am considering it. I consider “Spray Foam” a superior product than the others - So I won’t use them cause I can get my hands on “Spray Foam”

As for the foam, I am also not able to source "great stuff", which annoys me quite a bit. I live in the part of the world where shipping costs from Amazon usually are 2x the price of the product :D I know, its a first-world problem, but still.. I've done quite a bit of research into the "can" types of foam I am able to get hold of, and the best one I've found so far is PUR from Tec7 with a water absorption rate of 1% volume (https://tec7.com/storage/files/7d5b...6b42/purnovatechtecv2020-03-05-09-42-36en.pdf). Most other foam products have a lower rate of closed cells, and well, act more as a sponge I guess.

I would have to research the Tec7 as I am not familiar. If you can find a “spray foam” that will stick, has a good R value, & will not harm you with off gassing then I would use that.



Thanks for the reading material. I think, the PDF you linked me, I've read through it before, and thats the one that got me on the idea of using XPS over alternatives like polyiso. Also, as I can see from the table, XPS still performs fairly well in high temperature, although not as good as polyiso, so I am also considering using XPS in the whole van.

That choice would depend upon intended use - location & weather/climate; for me I want Polyiso in the walls & ceilings.

Mean Temp - doesn’t refer to “nasty” but “average”

How cold do you plan on using your van?
 

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Hi,
I would not use XPS in walls or ceiling because the max service temp is 165F and these areas could see temps in this area on rare occasions. DuPont (or DOW?) have lots of cautions on their website about keeping XPS from getting to hot - like don't leave it outside in the sun with the black lettering facing the sun - its not a fictional problem. As RV points out XPS is great for the floor, which won't see high temps.

On the insulation test I did under quite humid conditions the Polyiso did not pick up any water weight (sample weighed before and after to within a gram). So, XPS is no doubt better on moisture resistance, but Polyiso is probably good enough? People use Thinsulate and Wool, which are very permeable to water vapor, and I've not heard any horror stories from them about moisture problems.

The R value per inch of Poliso does go down with temperature, but it starts quite a bit higher than XPS and the crossover point where the Polyiso R value drops to the same value as XPS is quite low - about -10F outside temp. There are test data on the Building Science site on R value of Polyiso vs temperature. Its important when looking at this data to remember that the temperatures in the plots are the mean temperature of the insulation, so, if the outside temp is 0F and inside temp is 60F, the mean temp is 30F (not 0F). Even at lower -10F temps, the R value of Polyiso does not plummet, it just gets a bit lower than XPS.

Gary
Thanks @GaryBIS 100% agree !!

Sometime I am in some “mean” weather 😜

Tonight we are in the (mostly uninsulated) Cabin & got the Propex & Martin Wall Unit running. Nov 9 & not much snow on the ground. Definately need to get this cabin insulated or I am gonna go broke buying propane 💸💸💸.

At least we have about R24 of mineral wool on the roof (floor & walls - none).
 

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Hi RV,
I think its important when looking at the table that shows polyiso R values at different temps is that the 15F is the mean temp of the insulation. If the inside temp is (say) 60F, and the mean temp 15F, then the outside temp is -30F -- pretty chilly :) But, Foresty Forest did do -40F once, so not totally unreal :)
My reading of the test data on the Building Science site is that XPS and Polyiso have the same R value at about -10F outside with an inside temp of 60F.

Gary
I thought I saw a 🇨🇦 next to your Name Header the other day & I thought “Foresty Forest” must have gone to Banff 😁

Heading to Canada to look for some “real mean temperatures”.

I only use XPS on the floor & I totally agree with you & use polyiso in the walls & ceiling for the same reasons.

I also feel that “the total spray job” is the Cadillac system as “pseudo solves” the vapour barrier issue by makng the metal van skin to the warms side of the spray foam one thick vapour barrier.
 

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Discussion Starter · #37 ·
Thanks all for valuable input and ideas! There are indeed a lot of knowledgeable and experienced users in this forum :)

I used poly-iso for the floor, walls, and ceiling. On the walls and ceiling, it is glued in place and edge-sealed with a non-expanding spray foam (GreatStuff Doors and Windows).

In the doors and channels, I used a polyester batting product called Tyvek Thermawrap. It may not be available in your area, but it shows there are alternatives to Thinsulate. You want a material, like polyester, that is hydrophobic and will not compress or migrate over time from the vibration of driving. This is especially important when insulating inside doors that get slammed all the time. A spray contact-cement will help hold it in place.

@GaryBIS and others have also questioned the benefit of insulating small channels (roof ribs, etc). It is probably insignificant compared to the thermal bridging of the surrounding metal. It is probably better to focus on insulating the outside of those channels. However, thermal bridging is still evident on the bigger channels that I insulated inside. In cold weather, I see condensation on those exposed metal surfaces.
Thanks, I'll look more into what options I have in this regard. I've also seen the health concerns regarding different types of mineral wool, at least if not properly incapsulated. After all, I'd like to make a healthy living environment :)

I might also have to test my approach during the winter, and add a layer if it is not sufficient. For example, I'm planning on 25mm (1") Armaflex on the bulkhead and headspace section, so I guess I'll have to test this in practise to see if its sufficient (this is to save precious space, and also oddly shaped parts where its hard to fit solid insulation panels).

Regarding the ribs, all good and valid points. I'll make sure to cover all metal faces, after all, this is where most air is most likely to condensate first. My initial idea however, was that stuffing ribs with some sort of "soft insulation material" is a very quick and easy fix, if it adds any benefit that is.

Thank you for the detailed and insightful reply. May I ask why it is that you don't recommend any of the mineral wool of fabric types of material? Is it due to the fact that it will be "sandwiched" in between two vapor barriers, effectively?
Many reasons - But primarily due to the air transfer (think moist air & look at @GaryBIS tests). Hydrophobic or not dew can collect when air reaches the dew point. Also even Nasty Asbestos is safe when incapsulated 😳 - Whatever you believe in regards to friable “fiber shedding materials” fiberglass & mineral wool are at best uncomfortable to breath & @ worst cause health issues.


For example, unlike to roof ribs (which are quite small), the side ribs in the walls are quite big, and would leave a huge heat bridge if untreated. I will run conduit and cables through, but some are big enough to consider other types of "filler" material than spray foam I guess. Or at least, I am considering it. I consider “Spray Foam” a superior product than the others - So I won’t use them cause I can get my hands on “Spray Foam”

As for the foam, I am also not able to source "great stuff", which annoys me quite a bit. I live in the part of the world where shipping costs from Amazon usually are 2x the price of the product :D I know, its a first-world problem, but still.. I've done quite a bit of research into the "can" types of foam I am able to get hold of, and the best one I've found so far is PUR from Tec7 with a water absorption rate of 1% volume (https://tec7.com/storage/files/7d5b...6b42/purnovatechtecv2020-03-05-09-42-36en.pdf). Most other foam products have a lower rate of closed cells, and well, act more as a sponge I guess.

I would have to research the Tec7 as I am not familiar. If you can find a “spray foam” that will stick, has a good R value, & will not harm you with off gassing then I would use that.



Thanks for the reading material. I think, the PDF you linked me, I've read through it before, and thats the one that got me on the idea of using XPS over alternatives like polyiso. Also, as I can see from the table, XPS still performs fairly well in high temperature, although not as good as polyiso, so I am also considering using XPS in the whole van.

That choice would depend upon intended use - location & weather/climate; for me I want Polyiso in the walls & ceilings.

Mean Temp - doesn’t refer to “nasty” but “average”

How cold do you plan on using your van?
I might be reading too much into this though, who knows. Anyways, all of these polyethylene based products (adhesives and / or sealant products) like Great Stuff, as far as I can see are highly toxic (at least until cured). Now, having said that, I believe products made for indoors use obviously should be OK to use and not pose a health risk, even long term. But now, since I've been reading up on the safety data sheets on all these products (I'm probably the only one bothered to actually open these boring manuals :D), I've decided to go the route of some more environmental friendly and Isocyanate-free products. The downside of course is that they cost 3 times as much, but I'm willing to pay, at least for ease of mind. I'm probably being paranoid, this is the "no skills" part of me doing research of stuff I know little to nothing about, but I can live with being called paranoid just fine ;)

As for the insulation panels I've ordered aluminium face PIR panels from a Finnish company FinnFoam that make them for their saunas. If they can use it in their highly moist saunas, I surely can use it in my van :D

As for your other question. I will use the van for weekend trips to the mountains for skiing, and my more "long-term" plan is to quit my job and go around Europe for a year or two living in the van. So I wanted to prepare it, at least to a degree, to handle both hot and cold weather. When I say cold, it's not extremely cold, maybe -10degC give or take.

Thanks @GaryBIS 100% agree !!

Sometime I am in some “mean” weather 😜

Tonight we are in the (mostly uninsulated) Cabin & got the Propex & Martin Wall Unit running. Nov 9 & not much snow on the ground. Definately need to get this cabin insulated or I am gonna go broke buying propane 💸💸💸.

At least we have about R24 of mineral wool on the roof (floor & walls - none).
Maybe my math is completely wrong, but how do you get those extreme numbers? I mean, the PIR panels I'm looking at I'm looking at is rated to 0.022 W/mK. A thickness of 50mm should be around R=2,27? (0,05/0,022). My math is probably ****.. or maybe mineral wool is the way to go after all ;)
 

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Insulation took me a long time and I didn't do anywhere near the level of some people. I figure save a bit of headache and live a few degrees colder or burn a tiny bit more propane.
I bought a full set of window covers, black on one side, foil on the other. I turn them around as needed and find they REALLY help a TON holding heat in or out.
I used denim insulation in some cavities - I hear denim can mold, but I just don't see much water getting in there. Then again I'm on the west coast and southwest, and never experienced fabric molding. Those big lower C pillar cavities are open under cabinets and I can pull the insulation out easy if there's ever a problem.
The rest of the thermal bridges don't have such a huge air gap. I got a few rolls of 1/2x4 expansion joint foam and glued it over all the roof ribs and pillars as a thermal break and possibly a bit of insulation.

I didn't do the best nor the worst insulation job, but it stays warm for hours after it's cold out and we don't even use the heat much unless it's gonna be low 40s or colder. Just a bit in the evening and morning. For reference I grew up in the desert and hate cold.

The propex barely has to work to keep the van toasty all night in the 30s and 40s. Haven't tried 20s yet since finishing insulation. It did run a lot when we camped in the 20s and the windows and thermal bridges weren't covered yet, but so far I feel like the windows are the big one. More heat loss than a few exposed metal ribs. And the metal is mostly covered by other stuff even when not insulated.

Oh and also, in structural engineering we specify stainless or galvanized fasteners at all PT lumber.
Stainless fasteners should not be used to fasten to non-stainless metal, as it will cause the other metal to corrode when exposed to moisture.
 

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my more "long-term" plan is to quit my job and go around Europe for a year or two living in the van.
We have rented RVs in Europe many times. While planning this build, be aware of the differences you will face in terms of shorepower (220V) and propane (tank fittings differ by country). Also, the PM's Chrysler engine and tranny are not common over there, so parts and service may be hard to find. The European Fiat Ducato (and its clones) don't have Chrysler engines and trannys.
 

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Discussion Starter · #40 ·
Oh and also, in structural engineering we specify stainless or galvanized fasteners at all PT lumber.
Stainless fasteners should not be used to fasten to non-stainless metal, as it will cause the other metal to corrode when exposed to moisture.
Interesting. what types of fasteners are you suggesting I should use for PT wood then? I might just get regular wood for the rest of the van to avoid such headaches. Did not think of that.


We have rented RVs in Europe many times. While planning this build, be aware of the differences you will face in terms of shorepower (220V) and propane (tank fittings differ by country). Also, the PM's Chrysler engine and tranny are not common over there, so parts and service may be hard to find. The European Fiat Ducato (and its clones) don't have Chrysler engines and trannys.
As I'm already living in Europe (although not a part of the EU), the 230V is not going to be a problem. 110 would be the headache for me ;) I've also got the Ducato (hence the extra high roof, as apparently are not available in PMs), so I guess I'm set there too, although I have no idea about the engine. Its a 170hp diesel, thats all I know :)

As for the propane fitting, yes, I've heard that can be a pain too. I've not got that point in my planning yet, leaving that for later :)
 
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