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Old 09-20-2021, 05:30 PM   #1
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Thinsulate 3m?

I am building another bus out in montana. On my original bus I used 1.5" foam board insulation. The customer is convinced that we should be using 3M thinsulate. She has talked to several high end van builders in the area and they all swear by it. I've noticed in the bus community this insulation is usually frowned upon. With the metal roof it does seem like this type of reflective insulation would be effective. Is there a reason I shouldn't use it on the roof.

I also looked into spray foam but all the experts in the area are booked for two months. I could do it myself but many of the kits are on backorder. The one I did find is Versi-Foam 600 board feet. Anyone have experience with this?

I'd appreciate any feedback! I'm assuming thinsulate in the winter isn't great due to to conduction and convection heat loss?

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Old 09-20-2021, 06:09 PM   #2
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Originally Posted by mitchk View Post
I am building another bus out in montana. On my original bus I used 1.5" foam board insulation. The customer is convinced that we should be using 3M thinsulate. She has talked to several high end van builders in the area and they all swear by it. I've noticed in the bus community this insulation is usually frowned upon. With the metal roof it does seem like this type of reflective insulation would be effective. Is there a reason I shouldn't use it on the roof.

I also looked into spray foam but all the experts in the area are booked for two months. I could do it myself but many of the kits are on backorder. The one I did find is Versi-Foam 600 board feet. Anyone have experience with this?

I'd appreciate any feedback! I'm assuming thinsulate in the winter isn't great due to to conduction and convection heat loss?
What are you trying to accomplish with the insulation? If it's thermal insulation, 3M Thinsulate is useless for this. It's an acoustic insulator product.

https://www.3m.com/3M/en_US/p/d/b40068152/

If it's acoustic insulation your customer wants, it seems like a waste of money to acoustcally insulate the ceiling, when virtually all the noise comes from below.
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Old 09-20-2021, 06:35 PM   #3
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I'm not sure exactly what product you're referring to but I assume you mean this stuff or something similar. This has an R-value of around 3.5 per inch, similar to fiberglass or rock wool and significantly less than XPS foam board (R-5 per inch although this drops over time) or polyiso foam board (R-6.5 per inch although this drops off precipitously at temperatures below 75F so really shouldn't be used in cold-weather climates).

The product I linked doesn't seem to have a reflective layer, but for cold weather reflective layers are absolutely useless anyway. The amount of heat transferred via radiation (as opposed to conduction and convection) is a function of the absolute temperature taken to the fourth power, so it increases rapidly with increases in temperature but also decreases rapidly with decreases in temperatures. At the temps humans normally inhabit (say, 100F and lower) the amount of heat transferred by radiation as a percentage of the heat transferred via all methods combined (including conduction and convection) is effectively zero, so a reflective layer (which can only affect heat transfer via radiation) has no value. It is only with the high temperatures achieved by a vehicle out in direct sunlight (say, 140F and up) that a reflective layer becomes somewhat valuable, and obviously this will only be in hot-weather climates where you're trying to keep heat out of the vehicle rather than keep heat in the vehicle. Moreover, a reflective layer only works if it is adjacent to an air gap of at least 1" (and the air gap has to be vented to the outside), which is never the case with insulation packed tight into an internal cavity.

A lot of people use spray foam, but its insulation value is not significantly greater than that of foam board, and it costs roughly twice as much per board-foot. It is perhaps easier to install (especially in the curved roof), except that shaving off the excess looks like an especially un-fun and toxic task (never done it myself). Its main advantage over board is that if installed correctly it will completely fill the space with no gaps, which will definitively prevent condensation and leaking issues.
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Old 09-20-2021, 09:02 PM   #4
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Some of the professional van builders I watched on you tube preferred the thinsulate thermal insulation (no foil) to spay foam as the spray would sometimes deform the body panels in the van.

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Old 09-20-2021, 09:29 PM   #5
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This kinda reminds me of people saying WD-40 is a lubricant. It's not, but since they sell that way, a lot, the manufacturer doesn't correct people and just pockets the money. I get that. But... it's water displacement formula to prevent corrosion. You can tell when it dries it forms a thin film that can be washed off with a pressure washer or strong hose. The film also attracts dust very effectively, which means that if you think you're going to grease your car locks with it, you'll be calling the locksmith much sooner than later.

Same with 3M Thinsulate. The manufacturer advertises as what it is, acoustic insulation. But if someone wants to use it for toilet paper, who are they to argue?
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Old 09-20-2021, 11:44 PM   #6
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This kinda reminds me of people saying WD-40 is a lubricant. It's not, but since they sell that way, a lot, the manufacturer doesn't correct people and just pockets the money. I get that. But... it's water displacement formula to prevent corrosion. You can tell when it dries it forms a thin film that can be washed off with a pressure washer or strong hose. The film also attracts dust very effectively, which means that if you think you're going to grease your car locks with it, you'll be calling the locksmith much sooner than later.

Same with 3M Thinsulate. The manufacturer advertises as what it is, acoustic insulation. But if someone wants to use it for toilet paper, who are they to argue?
I'm not super-familiar with Thinsulate except for its use in cold-weather clothing as detailed in this other link from 3M. This product is perfectly adequate for thermal insulation as well as acoustic insulation, just not as good for thermal as the polyurethane foams.
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Old 09-21-2021, 12:22 AM   #7
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Thinsulate absolutely is thermal insulation and mostly used for that rather than just acoustic.

and industrial versions are widely used as such for van conversions.

Much easier to work with than most foams, less PPE required.

But relatively expensive R-value, and remember a tightly sealed vapour barrier is just as important

Can be a challenge to source in small quantities.

Cheap RV living had a member does it as a sideline.
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Old 09-21-2021, 12:24 AM   #8
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some links, sorry not live

Screenshot_20210921-012409.jpg
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Old 09-21-2021, 12:27 AM   #9
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I'm not super-familiar with Thinsulate except for its use in cold-weather clothing as detailed in this other link from 3M. This product is perfectly adequate for thermal insulation as well as acoustic insulation, just not as good for thermal as the polyurethane foams.
Thinsulate is a trademark, not a single product. It is just like the word "Ford", which is also a trademark, and the company makes a ton of different products under the trademark. Thinsulate SM600L acoustic insulation is composed of 35% polyester staple fibres, and 65% polypropylene fibres, and is not woven. Thinsulate thermal cloth comes in different formulations, but internally they are made from fibers composed of polyethylene terephthalate or a mixture of polyethylene terephthalate/polypropylene. These fibers are woven and made into various products -- seven different major categories of products that I could find.

The SM600L product does have thermal insulation properties, but as you stated, the R-factor is less than spray foam and polyiso foam board, and pretty much the same as pink board. SM600L uncompresses to 1-3/4" to 2" thick over weeks and comes in rolls. That means that you can't install more than one layer to improve the insulation if you want to be able to install panelling over it. That R value is all you will get, unless you want to see your panels bulge out as it expands over time.

It is also expensive. One site I just checked has it at $15 per linear foot if you buy 10 linear feet or more. A 170 wheel base Sprinter will need about 60-65 linear feet + the other supplies. Do the math and multiply for your size skoolie.

If someone thinks they will want to use the same Thinsulate you can find in gloves and clothing, good luck with that too. Thermal insulation factors for that product run from 1.6 to 2.9, and it sells for about $10 per 60"-wide yard.

So far I am planning to use spray foam on my bus, after carefully cleaning and treating/sealing the metal as best as possible. You have to do good prep, and the trimming and cleanup is messy, but applying the product is easy.
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Old 09-21-2021, 08:59 AM   #10
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I know vanlifers use this all the time. I haven't found any recommendations from the manufacturer suggesting this as a wall or ceiling insulation. Maybe I just didn't find the documentation and I'm totally wrong. The heavily used trademark name could corrupting my searches.

Is your customer is confusing wearable clothing with construction materials? Maybe just refer her to the manufactures product documentation.
https://www.3m.com/3M/en_US/thinsulate-us/

3M Thinsulate, is a down feather alternative, used between the layers of winter clothes. Jackets, gloves, boots.

Where did you find a manufacturer's recommendation, stating that 3M Thinsulate, is approved for use in a fire rated structure? Was an R rating listed? Burn time? Fire barrier requirements? Do you know the name or part # of a specific building material? I'll study it.

There are many fire and health risks created by insulating materials. Some (misused products) can contribute to the spread of a fire, while others produce smoke and toxic gases. The amount of insulation in the walls and ceiling/roof of a room can affect the rate of growth of a fire or whether-or-not the occupants have enough oxygen to escape.
https://www.amfam.com/resources/arti...tion-materials

The customer is rarely an all knowing, master-craftsman. Licensed, bonded, & insured building contractors are inspected by a third party government employee for the safety of the occupants. None of the aformentioned is required in a vehicle. When I (or my help) make mistakes, I'm grateful for the inspectors' QA checks.
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Old 09-21-2021, 10:22 AM   #11
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Sorry for the confusion all, the product is thinsulate SM600L. It sounds like it has an R-value of 3.5 while the XPS foam board I would use has 5.0. The only real benefit to the thinsulate would be the ease of installation.

I was under the impression that when using foam board insulation the general consensus was to use XPS as Polyiso board isn't near as effective in hotter or colder climates? I live in cold winter/ warm summer areas.
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Old 09-21-2021, 10:34 AM   #12
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Sorry for the confusion all, the product is thinsulate SM600L. It sounds like it has an R-value of 3.5 while the XPS foam board I would use has 5.0. The only real benefit to the thinsulate would be the ease of installation.
Foam board is pretty easy to install also, except maybe in the curved ceiling.

Quote:
Originally Posted by mitchk View Post
I was under the impression that when using foam board insulation the general consensus was to use XPS as Polyiso board isn't near as effective in hotter or colder climates? I live in cold winter/ warm summer areas.
Polyiso is more effective than XPS in warm weather (> 75F), R-6.5 vs. R-5. But its R-value drops off in cold temperatures, down to R-2 at 15F. Since the insulation is normally heated to ~70F on the inside, the net R-value when it's 15F outside would be about R-4, which is the rating builders generally give polyiso when it's used in cold-weather cilmates. But if the temperature continues to drop below 15F the net R-value of polyiso will continue to drop as well.

XPS, like pretty much every other type of insulation except polyiso, will have an R-value that increases somewhat at lower temperatures.
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Old 09-21-2021, 10:50 AM   #13
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I follow a golden rule that I think will serve me well on my skoolie. The best insulator is air. That's why you are told since you are a child that if you go outside when it's cold you should wear layers of clothing. So I look for insulating material that applies this rule, plus has properties like hydrophobia to not absorb moisture and turn into a mass of mold, fire resistance (SM600L does have this, it is self-extinguishing), etc.

For example, I've seen a few videos and websites of millennials touting sheep's wool insulation as the product to use (with the accompanying ukelele music and video of a screaming goat, no, I have no idea why). Sure, the fibers leave lots of space for air, but what they don't tell you or (worse yet) don't know is that it has an R-factor of around 3.5 and it will absorb up to 33% of its volume in moisture. Oof.
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Old 09-21-2021, 12:45 PM   #14
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From controlled experiments in the construction of custom fridge/freezer boxen

when such very cold temps are involved

the ideal R-value per inch is achieved by a thin layer of XPS (or EPS) on the cold side, say 10-20% of the total wall thickness

and PolyIso for the remainder, in this case on the inside.
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Old 09-21-2021, 12:49 PM   #15
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Using air cavities as insulation is not practical in extreme conditions for mobile applications, when total wall thickness needs to be minimized.

And yes, any "organic" materials will end up hosting critters and absorbing moisture.

Rock wool is **maybe** one exception, but is hard to work with.
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Old 09-21-2021, 01:29 PM   #16
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From controlled experiments in the construction of custom fridge/freezer boxen

when such very cold temps are involved

the ideal R-value per inch is achieved by a thin layer of XPS (or EPS) on the cold side, say 10-20% of the total wall thickness

and PolyIso for the remainder, in this case on the inside.
Eureka! There's the answer! Cover the outside of the bus with thin pink foam board insulation!
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Old 09-21-2021, 01:31 PM   #17
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Using air cavities as insulation is not practical in extreme conditions for mobile applications, when total wall thickness needs to be minimized.

And yes, any "organic" materials will end up hosting critters and absorbing moisture.

Rock wool is **maybe** one exception, but is hard to work with.
I was taking in terms of using materials that contain a large percentage of air in small cavities.
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Old 09-25-2021, 06:05 PM   #18
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Stalking this post

I am stalling for time before jumping down this rabbit hole. But know if I am ever to use my bus for anything other than a drivable storage shed, my wife will insist on air conditiioning. On an island of average 85 to 95 degrees and 95 percent humidity, heavy insulation is a must to trap the dew point. Compounding my issues are supply difficulties as sadly home depot is the prime scource. (Two other hvac suppliers too). I just wanted to chime in here as this is the next dillema to iron out. ( seems a roof raise is inevitable once factoring celing and floor insulation. For radiant issues i plan to use elastomeric coating on roof at first and I have a pile of unistrut i intend to use to make a patio/solar mount/ flatish roof to shade the curved bread loaf roof of the blue bird. I appreciate reading imput of those further along this road.
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Old 09-25-2021, 06:08 PM   #19
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I am stalling for time before jumping down this rabbit hole. But know if I am ever to use my bus for anything other than a drivable storage shed, my wife will insist on air conditiioning. On an island of average 85 to 95 degrees and 95 percent humidity, heavy insulation is a must to trap the dew point. Compounding my issues are supply difficulties as sadly home depot is the prime scource. (Two other hvac suppliers too). I just wanted to chime in here as this is the next dillema to iron out. ( seems a roof raise is inevitable once factoring celing and floor insulation. For radiant issues i plan to use elastomeric coating on roof at first and I have a pile of unistrut i intend to use to make a patio/solar mount/ flatish roof to shade the curved bread loaf roof of the blue bird. I appreciate reading imput of those further along this road.
A good dehumidifier might also be called for. It will do wonders to make the interior space much more livable. Here is one inexpensive option.

https://www.amazon.com/dp/B0014TMXVA...v_ov_lig_dp_it
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Old 09-25-2021, 06:25 PM   #20
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In each of our apartments we can get up to 2 gallons a day of condensate from our split units, and with 8" of concrete (no appreciable r value?) Walls sweat it more than five degrees of temp difference. I worry if ac turned down for comfort, exterior sweating is my concern. Steel body or cars dont last here being bad enough but not trapping dew point is sentencing the bus to early death. Hope to learn of different products so i can acheive my goal with less than 5" of insulation or 4k (I hope either is realistic) i have a little kubota genset to put in a doghouse on front bumperette where one of two engine druven ac pumps will run off genset (also share coolant and radiator of main engine) and a mini split to run off of shore power. (Also of note in my avitar photo picturing my bus in front of my building, beyond and behind is another building, a cross street and the west facing shore.) Corrosion is the price of paradise
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