[antmanv1]

I did some tests of the insulation types commonly used to insulate van conversions. It seems like there are so many claims and opinions on the best type of insulation to use in van conversions, that some actual data might be helpful to people trying to decide (the other factor is that I’m Covid bored and really needed a project to work on).

I used this test box in which the temperature and humidity can be controlled. It has 4 bays that allow insulation samples to be installed and their performance compared side by side.

For this test, left to right, its Polyiso, Thinsulate and Wool plus bay with no insulation.

Mostly I was testing for how the insulations handle moisture and condensation, but also some IR pictures to compare thermal performance and have also started a mold test.

This is quite a bit of data and all the details are here: Insulation Testing – For Van Conversions – Build A Green RV
But, some highlights below...

The first test compares Wool, Thinsulate and Polyiso.

The parameters that are measured and logged during the test are:

• Temperature and relative humidity inside the box
• Temperature and humidity outside the box
• Humidity in the middle of each insulation sample
• Initial and final weights of each insulation sample (to measure moisture accumulation)
• Thermal camera pictures for rough assessment of thermal performance

Generally a test run starts by weighing and then installing each insulation sample in its own bay. Then the inside of box temperature and humidity are set on the controller. The test is then run for a time roughly equal to a night in an RV. Photos and IR pictures are taken once in a while during the test to record condensation levels and see if there are any changes in thermal performance. At the end of this period, the insulation samples are weighed to get water pickup, and then quickly reinstalled. Then the humidifier is turned off while the heater is left on, and ventilation is increased to get a warm and dry environment in the box for drying. The test then continues until all of the insulation samples have dried out, and a final weight of each sample is taken.

Condensation:
The main goal of the test was to see how much condensation forms for the different insulation types both on the cold van wall and in the outer layers of the insulation. To test this, the box was kept at 70F and 70% relative humidity for about 14 hours - kind of a typical camping night. Outside temperature was about 40F.

The front wall of the box is made from Plexiglass so that the condensation can be directly observed.
Here is one set of pictures that shows the extent of condensation near the end of the test.

This is the Plexiglass with no insulation and the Wool insulation:

Plexiglass on right and wool on left.

This is the Thinsulate and Polyiso at the same time:

Thinsulate on right and Polyiso on left.

The Plexiglass of course forms lots of condensation (like a window on the van), the Thinsulate is next with quite a bit on condensation on the Plexiglass and in the outer part of the Thinsulate batt, and the Wool also (by this time) has a significant amount of condensation, the Polyiso does not show any condensation.

The details link up above has closeups and more detail on how long it took each kind of insulation to form condensation.

The Thinsualte and Wool do behave differently - the wool (it appears) absorbs some of the moisture in its fibers and this delays the formation of condensation compared to the Thinsulate. This may or may not be an advantage depending on what you think about the insulating material absorbing moisture -- some would feel this is not a good thing.

Weighing the batts for moisture absorption:
I weighed each of the insulation at start of test (dry), and after a nights worth of humid conditions (max moisture), and then again after a drying period.
The table below shows the results on moisture pick up for each insulation.

Insulation	Starting Weight (grams)	End humid period (grams)	Humid period gain (grams)	End drying period (grams)	Gain over test (grams)
Wool	768	804	36	782	14
Thinsulate	640	651	11	641	1
Polyiso	270	270	0	270	0

Hopefully the table does not get mangled by the forum software, but each insulation performs differently.

Polyiso does not absorb any moisture throughout the whole test.

Thinsulate absorbs 11 grams of water in the batt, and manages to dry all but 1 gram out during the drying period.

Wool absorbs 36 grams of water in the batt, and manages to dry 22 grams out during the drying period, but still retains 14 grams at the end of the drying period. This raises the possbility that there will be less capacity to absorb moisture the next night.



Humidity Level in Batts:
I put a humidity logger half way into the thickness of each of the insulation - the next three pictures show humidity levels in the middle of each insulation batt for the test...

Wool:

Thinsulate:

Polyiso:

They do behave differently.
The Thinsulate rapidly rises to a high level and then stays there for the duration.
The Wool rises more gradually, but eventually gets to about the same high level.

The Polyiso gradually rises to a lower max level. But, not sure the Polyiso readings are that valid in that the way the humidity level is measured probably allowed a bit of air to leak into where the sensor was.


Thermal Performance IR pictures:
I wanted to get a rough idea if the condensation that forms in the fiber insulations reduced R value, so took IR pictures when the insulations were dry and then again after a nights worth of condensation.

This is the dry IR picture:

and, this is the picture after 14 hours of condensation:

Not a whole lot of difference, so I'd say the condensation in the fiber insulations does not degrade R value too much (surprising to me).


Conclusions:
First, I would encourage everyone to read over the test details and see what they mean to you in your situation.

Beyond that, here are a few things that seem pretty obvious…

• Judging by thermal pictures, all of the insulation types tested do insulate! And, it appears that for the level of condensation in this test, the insulating properties (R values) are not strongly effected by the condensation (which surprised me).
• Both of the fiber insulations (wool and Thinsulate) do allow water vapor to penetrate and condense both in the outer layers of insulation and on the van wall. The Polyiso with sealing around the edges did not let water vapor penetrate and does not condense water on either its outer or inner face.
• The wool appears to have less visible condensation than the Thinsulate – probably due to some of the water being absorbed into the wool itself. Havelock calls this moisture management, but others would say that having insulation absorb water into its fibers is just not a good thing. Take your choice

I'd be very interested in what peoples thoughts are on this??

Again, much more detail here: Insulation Testing – For Van Conversions – Build A Green RV
Also have a mold test going, which is explained at the link.

Gary

very well done! I haven't read your bio, but you must be an engineer. if not you are one anyway. ppl get paid big bucks for the type of work you did here. I'm impressed coming from a manufacturing. thanks for sharing your with us. that's a real service you provided. btw- I'm in need of this very upgrade now, so it's helpful with my research to have this data.

here's my "bare canvas" ;-)

 

[antmanv1]

I did some tests of the insulation types commonly used to insulate van conversions. It seems like there are so many claims and opinions on the best type of insulation to use in van conversions, that some actual data might be helpful to people trying to decide (the other factor is that I’m Covid bored and really needed a project to work on).

I used this test box in which the temperature and humidity can be controlled. It has 4 bays that allow insulation samples to be installed and their performance compared side by side.

For this test, left to right, its Polyiso, Thinsulate and Wool plus bay with no insulation.

Mostly I was testing for how the insulations handle moisture and condensation, but also some IR pictures to compare thermal performance and have also started a mold test.

This is quite a bit of data and all the details are here: Insulation Testing – For Van Conversions – Build A Green RV
But, some highlights below...

The first test compares Wool, Thinsulate and Polyiso.

The parameters that are measured and logged during the test are:

• Temperature and relative humidity inside the box
• Temperature and humidity outside the box
• Humidity in the middle of each insulation sample
• Initial and final weights of each insulation sample (to measure moisture accumulation)
• Thermal camera pictures for rough assessment of thermal performance

Generally a test run starts by weighing and then installing each insulation sample in its own bay. Then the inside of box temperature and humidity are set on the controller. The test is then run for a time roughly equal to a night in an RV. Photos and IR pictures are taken once in a while during the test to record condensation levels and see if there are any changes in thermal performance. At the end of this period, the insulation samples are weighed to get water pickup, and then quickly reinstalled. Then the humidifier is turned off while the heater is left on, and ventilation is increased to get a warm and dry environment in the box for drying. The test then continues until all of the insulation samples have dried out, and a final weight of each sample is taken.

Condensation:
The main goal of the test was to see how much condensation forms for the different insulation types both on the cold van wall and in the outer layers of the insulation. To test this, the box was kept at 70F and 70% relative humidity for about 14 hours - kind of a typical camping night. Outside temperature was about 40F.

The front wall of the box is made from Plexiglass so that the condensation can be directly observed.
Here is one set of pictures that shows the extent of condensation near the end of the test.

This is the Plexiglass with no insulation and the Wool insulation:

Plexiglass on right and wool on left.

This is the Thinsulate and Polyiso at the same time:

Thinsulate on right and Polyiso on left.

The Plexiglass of course forms lots of condensation (like a window on the van), the Thinsulate is next with quite a bit on condensation on the Plexiglass and in the outer part of the Thinsulate batt, and the Wool also (by this time) has a significant amount of condensation, the Polyiso does not show any condensation.

The details link up above has closeups and more detail on how long it took each kind of insulation to form condensation.

The Thinsualte and Wool do behave differently - the wool (it appears) absorbs some of the moisture in its fibers and this delays the formation of condensation compared to the Thinsulate. This may or may not be an advantage depending on what you think about the insulating material absorbing moisture -- some would feel this is not a good thing.

Weighing the batts for moisture absorption:
I weighed each of the insulation at start of test (dry), and after a nights worth of humid conditions (max moisture), and then again after a drying period.
The table below shows the results on moisture pick up for each insulation.

Insulation	Starting Weight (grams)	End humid period (grams)	Humid period gain (grams)	End drying period (grams)	Gain over test (grams)
Wool	768	804	36	782	14
Thinsulate	640	651	11	641	1
Polyiso	270	270	0	270	0

Hopefully the table does not get mangled by the forum software, but each insulation performs differently.

Polyiso does not absorb any moisture throughout the whole test.

Thinsulate absorbs 11 grams of water in the batt, and manages to dry all but 1 gram out during the drying period.

Wool absorbs 36 grams of water in the batt, and manages to dry 22 grams out during the drying period, but still retains 14 grams at the end of the drying period. This raises the possbility that there will be less capacity to absorb moisture the next night.



Humidity Level in Batts:
I put a humidity logger half way into the thickness of each of the insulation - the next three pictures show humidity levels in the middle of each insulation batt for the test...

Wool:

Thinsulate:

Polyiso:

They do behave differently.
The Thinsulate rapidly rises to a high level and then stays there for the duration.
The Wool rises more gradually, but eventually gets to about the same high level.

The Polyiso gradually rises to a lower max level. But, not sure the Polyiso readings are that valid in that the way the humidity level is measured probably allowed a bit of air to leak into where the sensor was.


Thermal Performance IR pictures:
I wanted to get a rough idea if the condensation that forms in the fiber insulations reduced R value, so took IR pictures when the insulations were dry and then again after a nights worth of condensation.

This is the dry IR picture:

and, this is the picture after 14 hours of condensation:

Not a whole lot of difference, so I'd say the condensation in the fiber insulations does not degrade R value too much (surprising to me).


Conclusions:
First, I would encourage everyone to read over the test details and see what they mean to you in your situation.

Beyond that, here are a few things that seem pretty obvious…

• Judging by thermal pictures, all of the insulation types tested do insulate! And, it appears that for the level of condensation in this test, the insulating properties (R values) are not strongly effected by the condensation (which surprised me).
• Both of the fiber insulations (wool and Thinsulate) do allow water vapor to penetrate and condense both in the outer layers of insulation and on the van wall. The Polyiso with sealing around the edges did not let water vapor penetrate and does not condense water on either its outer or inner face.
• The wool appears to have less visible condensation than the Thinsulate – probably due to some of the water being absorbed into the wool itself. Havelock calls this moisture management, but others would say that having insulation absorb water into its fibers is just not a good thing. Take your choice

I'd be very interested in what peoples thoughts are on this??

Again, much more detail here: Insulation Testing – For Van Conversions – Build A Green RV
Also have a mold test going, which is explained at the link.

Gary

my conclusion based on the data is that polyiso is a preferable product for a van application. The insulation cgaracteristics are superior and the condensation test was impressive. I would choose the polyiso, personally. thanks for the great test!

 

[G-42]

my conclusion based on the data is that polyiso is a preferable product for a van application. The insulation cgaracteristics are superior and the condensation test was impressive. I would choose the polyiso, personally. thanks for the great test!

Plus it's cheap and easy to work with...

 

[h1k3rb]

And it's light as a feather. I'd think wool, especially when damp would add a lot of unnecessary weight.

 

[el Jefe]

Plus it's cheap and easy to work with...

I will add that 1", 3/4" and 1/2" are all good sizes to use. 2" is definitely tough to use as it does not conform well to the subtle curves in the sheet metal carcass.

You can use 3M-90 or brushable contact cement to adhere and layer as needed.

Great Stuff Crack & Window to finish it out.

 

[Dennis CampMaker]

I will add that 1", 3/4" and 1/2" are all good sizes to use. 2" is definitely tough to use as it does not conform well to the subtle curves in the sheet metal carcass.

You can use 3M-90 or brushable contact cement to adhere and layer as needed.

Great Stuff Crack & Window to finish it out.

I used great stuff to glue the polysio to the wall and then great stuff to fill the edges. I think it "glues" to the wall better than other options. I have read about many other "glues" that fail to hold the foam securely.

 

[jagarcia89]

Interesting stuff. Thank you.

On my last build I used polyiso but intentionally left space behind it for an air gap and condensation using great stuff. I’m wondering if that was the wrong way to go?

As for transit forums with thinsulate, I often wonder how much of build trends has to do with well known builds/builders. Faroutride is a very popular and helpful couple/site/build. So I wonder if when people do their transit research and inevitably stumble across them and their well done write up on thinsulate in a transit, they end up going that way.


Sent from my iPhone using Tapatalk

 

[el Jefe]

Interesting stuff. Thank you.

On my last build I used polyiso but intentionally left space behind it for an air gap and condensation using great stuff. I’m wondering if that was the wrong way to go?

As for transit forums with thinsulate, I often wonder how much of build trends has to do with well known builds/builders. Faroutride is a very popular and helpful couple/site/build. So I wonder if when people do their transit research and inevitably stumble across them and their well done write up on thinsulate in a transit, they end up going that way.


Sent from my iPhone using Tapatalk

I don't think there was anything wrong with what you did. Whatever makes the insulation stick to the carcass should work. Using 90 or contact cement in the center of the panel leaving a vertical path for any condensation should be good.

There is good science behind keeping your interior heat from passing to a cold carcass and creating condensation against a cold surface. Leaving a gravity path, just in case, is just a good idea.

This is not rocket science folks.

 

[gehughes]

This really is quite incredible and none of the other engineers are giving you enough credit. Amazing that you went through this trouble and it is so much appreciated. There’s only one conclusion that can be drawn for me as someone who hasn’t yet insulated...polyiso it is. Done. But I do wonder why everyone seems to use 1” polyiso instead of 2” when between the ribs of the van there’s plenty of room for almost 3”. Why would you only use 1” of insulation?

 

[jagarcia89]

This really is quite incredible and none of the other engineers are giving you enough credit. Amazing that you went through this trouble and it is so much appreciated. There’s only one conclusion that can be drawn for me as someone who hasn’t yet insulated...polyiso it is. Done. But I do wonder why everyone seems to use 1” polyiso instead of 2” when between the ribs of the van there’s plenty of room for almost 3”. Why would you only use 1” of insulation?

I did 3/4 last time. I was in Florida it’s what was in stock and no one would even special order thicker sheets at the time without charging 3x the material cost in shipping.


Sent from my iPhone using Tapatalk

 

[GaryBIS]

Hi,
To me, the nice thing about Polyiso from a moisture control point of view is that its not permeable to water vapor, so if its sealed well to the van sheet metal, then you won't get condensation on the cold van sheet metal because the water vapor just can't get there. And, the inside surface of the Polyiso is normally going to be above the dew point, so you won't get condensation on the inside of the Polyiso either. Its a totally dry system.

This technique of adding nonpermeable insulation as the outside layer of insulation has become pretty common in house insulation. Something like Polyiso or XPS is used as the outer layer typically on the outside of the sheathing. This outer insulation thickness varies with climate, but is chosen such that the dew point temperature occurs within the Polyiso -- the idea being that you will never get any actual condensation in the wall because the Polyiso is not permeable to water vapor, so the water vapor just can't get get to a cold enough part of the insulation stackup to condense.

The potential downsides of insulations that do allow penetration of water vapor to the van skin is that you will get condensation under some circumstances, and there is at least some risk of rust or mold. It seems to me that the risk of rust is probably low -- especially with the PM's galvanized body panels. In the farm field across from us is a lovely old McCormick-Deering1930's combine with galvanized body panels -- after 50+ years of sitting out in summer rains and winter snows these galvanized panels are still hanging in there.
The mold risk is unknown to me -- there are certainly reports of mold in RVs, but I've not heard reports of our kind of conversion vans growing mold. The mold test I'm in the middle of may shed some light on this. But, even if the risk associated with condensation on the van skin and in the outer layers of insulation is low, I'm just wondering why take the risk? Routinely having liquid water inside the wall is not something you would tolerate in a well designed home.

All that said, I can see why people like Thinsulate -- its probably the quickest and easiest of the bunch to install and even though it does let water vapor through it, it does not absorb the condensation water into the fibers.

And, I can also see why people like Wool. Its just lovely stuff to work with -- you can bury your face into it and it just feels like a soft sweater. Its a natural product and those concerned about chemical sensitivities might find it more acceptable. It would be nice to know how much fact there is to the idea that its healthier than Polyiso. That is, as appealing it is that sheeps wool is natural product, is there really anything in Polyiso that can be a health problem any more than sheeps wool?

Just my 2 cents at this point -- certainly open to hearing other opinions.

Gary

 

[RDinNHandAZ]

The house I built in NH in 2010 has 2’ of XPS outside of R13 fiberglass with an interior vapor barrier. In designing it I spoke to an insulation specialist and engineer about the moisture/condensation issue. They maintained that the XPS does allow limited vapor to move through avoiding the dreaded double vapor barrier that traps moisture in walls. It also moves the dew point inside the foam further avoiding condensate on the exterior sheathing surface.
These things are very important in our vans where avoiding the two vapor barriers is problimatic due to the exterior metal surface. I advocate for Polyisocyanurate even though it has vapor barriers on its aluminized surfaces. Lowering the condensate load and moving the dew point into the foam has to help in the accumulation of liquid water. XPS would be a good choice except it degrades beginning about 160º F and the van sitting in the sun can get a surface temperature in excess of that. DAMHIK.
Thinsulate, fiberglass, wool and other fibered insulation may be very effective insulation even when wet but they do hold moisture on their fibers. All are hydrophobic making them better than other fibers like denim which absorb and hold moisture in their fibers, but they rely on there being low moisture inside the van and enough time for re-evaporation of condensate into the interior air. All van dwellings need lots of ventilation which works against efficient heating. The other downside of fibered insulation is it needs to be encapsulated so the insulating air in it gets trapped and held still. Only then will it reach its rated R value. Home fiberglass works well if inserted into a wall or ceiling cavity that is sealed on all 6 sides and edges. It took builders almost 50 years to optimize its use. Many homes are capped with a layer of it between the joists or trusses, leaving one surface open which reduces it to a fraction of its rating. Your house may be insulated like this. This sort of insulating is problematic in a van where enclosing the fibered insulation is hard to do well enough to air seal it. Air can move through the fibers and the insulattion will have less than optimium effectivness. Sealing it may lead to additional vapor barrier layers with the potential to trap condensate against the van’s skin. Having sealed it evaporation will be slow at best and may lead to continual moisture in the fibers. Using a product on the interior like Tyveck or Typar may help as it can cut off the movement of air and liquid but will allow vapor to escape back into the ventilated van.
My many years of home renovation have revealed every conceivable form of water damage and the resulting rot and mold and degraded insulation. Our vans are not likely to rot out but mold and rust are a real possibility.

 

[phil]

...But I do wonder why everyone seems to use 1” polyiso instead of 2” when between the ribs of the van there’s plenty of room for almost 3”. Why would you only use 1” of insulation?

Depends on what climate you camp in. 1/2"-1" polyiso and a parking heater will work for most people, I'm not going to surrender space for a small gain in R value. I bet I could get away with 1/2" with my heater.

I don't have any experience with hot and humid, that's the tough one.

 

[supermoocow]

This really is quite incredible and none of the other engineers are giving you enough credit. Amazing that you went through this trouble and it is so much appreciated. There’s only one conclusion that can be drawn for me as someone who hasn’t yet insulated...polyiso it is. Done. But I do wonder why everyone seems to use 1” polyiso instead of 2” when between the ribs of the van there’s plenty of room for almost 3”. Why would you only use 1” of insulation?

We used 2" in the lower portions of the van, since otherwise it would just be dead air space. There was room for another 1/2" in most places, but it didn't seem worth the cost/effort for so little extra benefit. It may provide little benefit in most places, but I could see it being helpful behind the kitchen cabinets, since with the doors closed not much heat gets in and I don't want the water pipes to freeze.

 

[el Jefe]

This really is quite incredible and none of the other engineers are giving you enough credit. Amazing that you went through this trouble and it is so much appreciated. There’s only one conclusion that can be drawn for me as someone who hasn’t yet insulated...polyiso it is. Done. But I do wonder why everyone seems to use 1” polyiso instead of 2” when between the ribs of the van there’s plenty of room for almost 3”. Why would you only use 1” of insulation?

I layered the polyiso. Think 2 layers of 1" plus in some areas, a third layer of 1/2 or 3/4" as it was easier to follow the curvature of the van skin.

And kudos to Gary for his efforts. Keep it up!

 

[RV8R]

The house I built in NH in 2010 has 2’ of XPS outside of R13 fiberglass with an interior vapor barrier. In designing it I spoke to an insulation specialist and engineer about the moisture/condensation issue. They maintained that the XPS does allow limited vapor to move through avoiding the dreaded double vapor barrier that traps moisture in walls. It also moves the dew point inside the foam further avoiding condensate on the exterior sheathing surface.
These things are very important in our vans where avoiding the two vapor barriers is problimatic due to the exterior metal surface. I advocate for Polyisocyanurate even though it has vapor barriers on its aluminized surfaces. Lowering the condensate load and moving the dew point into the foam has to help in the accumulation of liquid water. XPS would be a good choice except it degrades beginning about 160º F and the van sitting in the sun can get a surface temperature in excess of that. DAMHIK.
Thinsulate, fiberglass, wool and other fibered insulation may be very effective insulation even when wet but they do hold moisture on their fibers. All are hydrophobic making them better than other fibers like denim which absorb and hold moisture in their fibers, but they rely on there being low moisture inside the van and enough time for re-evaporation of condensate into the interior air. All van dwellings need lots of ventilation which works against efficient heating. The other downside of fibered insulation is it needs to be encapsulated so the insulating air in it gets trapped and held still. Only then will it reach its rated R value. Home fiberglass works well if inserted into a wall or ceiling cavity that is sealed on all 6 sides and edges. It took builders almost 50 years to optimize its use. Many homes are capped with a layer of it between the joists or trusses, leaving one surface open which reduces it to a fraction of its rating. Your house may be insulated like this. This sort of insulating is problematic in a van where enclosing the fibered insulation is hard to do well enough to air seal it. Air can move through the fibers and the insulattion will have less than optimium effectivness. Sealing it may lead to additional vapor barrier layers with the potential to trap condensate against the van’s skin. Having sealed it evaporation will be slow at best and may lead to continual moisture in the fibers. Using a product on the interior like Tyveck or Typar may help as it can cut off the movement of air and liquid but will allow vapor to escape back into the ventilated van.
My many years of home renovation have revealed every conceivable form of water damage and the resulting rot and mold and degraded insulation. Our vans are not likely to rot out but mold and rust are a real possibility.

Thanks RD for this post & detailing your findings with home renovations & the types of water damage you have discovered over the years. Our 2 perspective Countries build a little different & may have slightly different needs, however assumingely the Building Science follows the same physics albeit the Building Codes will vary from place to place. For “buildings” in Canada the “elimination” of interior air/vapour transfer into the wall/ceiling is performed by an polyethylene sheet just behind the drywall which is required by code to be totally sealed. Everything past that towards the exterior is to have the ability of air water vapour transfer.

The majority of the damage water has cause to the many building I have repaired has been water that has “ingress” into the wall/roof system from the exterior “rain”. Where condensation or increased moisture content of the wood framing materials is a concern in buildings, it is “easily” eliminated by the “poly” air/vapour barrier behind the drywall (at least in Canada). That leaves exterior water ingress as the majority culprit of rotting and moulding issues in buildings here.

So our vans as you know are very different & pose a real different problem for us to solve. When I decided to DIY build a van in late 2018 I researched what other DIYers were doing & wanted to find a preferred method or “best practices” 😳 OMG, there are many opinions out there and very few backed up with building science that I am aware of. I was very surprised of what I found, however some of it was good. I did not find any website that in my mind had a solution to the “Van Skin”. One of the websites that stuck out for me “@ the time” was @GaryBIS (although I was not interested in building a green van as mine was white).

Lucky for me I have a background in “Building Science” for buildings not vans. I was quickly able to eliminate things like denim. I searched & searched the internet for “the silver bullet”. None be found, I concluded on 2 basic systems;

1) Total Spray Insulation Job
2) Board Insulation (Polyiso walls & ceiling / XPS high load on floor)

I am still not convinced one is better than another here. My “feelings” are a “total spray insulation job” is best with the exception of possible van skin leaks allowing water ingress & the “freeze thaw” cycle causing issues. The total spray job “if properly installed” (with xps on the floor) almost eliminated the “interior condensation issue”.

Having chosen method #2 above, I then turned my attention to reducing as much mould food introduced into the ceiling/walls/floor as practical (I have plywood backing for my roof fan (IIRC 16” square with a 14” square cutout) & a small plywood blacking in my wall for shore power) - other than that “no wood” & I ensured the van surfaces were clean prior to insulating (dirt & debris can also be mould food).

My ceiling, wall, & floor surfaces are all plywoods treated/sealed with mould killing paint. Plywoods in themselves are considered air/vapour barriers albeit the joints & fastner holes make them non-continuous.

That was the best system I could dream up (yes I have gravity drainage pathways 🤞that I hope work if I get liquid water behind my structures).

The other side to this is “Van Use” & being diligent in moisture reduction. We all use our vans differently. Our Mileage May Vary, however I am going to do what is practical for how we use our van. One thing. Could do better at is remembering to open my roof vent when the van is being stored (this depends upon conditions & counter productive if rain water can get in).

@GaryBIS I can not thank you enough for your experiments & posting your results. The “wet” R values of the wool & Thinsulate were surprisingly high to me & good to know.

My perspectives however remains the same as before these tests & it does not come from the “reasons” to use wool or Thinsulate rather it comes from the reasons not to use XPS, Polyiso, or Spray Insulation. I consider the later to be superior products for the job. I would like to hear the opinions of other DIYers.

So For All Forum Members; Is there any reasons to “not use” XPS, Polyiso, Spray Insulation?

 

[supermoocow]

If we ever built another van, we would consider thinsulate for ease of insulation. Installing the polyiso and spray foam was pretty tedious and time consuming.

 

[GaryBIS]

Hi RV,
Got a good laugh out of "One of the websites that stuck out for me “@ the time” was @GaryBIS (although I was not interested in building a green van as mine was white). "

I'll have to talk to my daughter (who came up with the name) about this!

Gary

 

[RDinNHandAZ]

RV8R,
We use the same systems to build I bet, based on the “International Building Code” which requires a vapor barrier inside the insulation in the walls. Outside that we also build to let vapor escape to the outside. That is why I researched the permeability of the EXP.
We also agree on insulating a van but you would be surprised how many still use denim or multiple vapor barriers in theirs.
Gary,
If your research is not headed then the stuff growing in the badly insulated walls may be GREEN.

 

[RV8R]

If we ever built another van, we would consider thinsulate for ease of insulation. Installing the polyiso and spray foam was pretty tedious and time consuming.

Thanks @supermoocow that is the type of “reason(s)” I am interested in hearing.

I have never worked with Thinsulate, so I am not familiar with how “easy” it is to install.

Ease of labour is a good reason to use one product over another.