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Old 11-02-2021, 12:15 PM   #1
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Thermal bridging???

So I get the basic idea if thermal bridging. With all the info I'm reading, I'm wondering if it makes sense to put a barrier between the furring strips and the metal?

I was thinking a Dynamat, Noico kind of layer.

Not sure if this is a bad idea or just ridiculous overkill?

Any thoughts?

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Old 11-02-2021, 01:04 PM   #2
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I don't know that dynamat has much if any R-value, but I like the idea of a small barrier between the metal and the furring. I was pondering the use a thin layer of Cork insulation or floor underlayment. I think some people use rubber or butyl strips (is dynamat butyl?) but I'm not sure what if any R-value that would give (at the very least its better than metal).
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Old 11-02-2021, 01:11 PM   #3
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I used sill seal over the ribs when I reinstalled my metal ceiling after sprayfoaming.
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Old 11-02-2021, 01:43 PM   #4
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It'd be a good idea if reinstalling the metal ceiling.

Metal outer skin - metal frame - metal inner skin I would think would be pretty thermally conductive. Disrupting that with a butyl or softwood strip would disrupt a lot of that heat transfer. Fasteners used would still bridge heat, but not at that high of a rate. A 4x8 sheet of luan cut down into strips and used as furring would work better then a steel-steel contact, and it wouldn't be prohibitively expensive either.

If the inner skin is ship lap, or another wood product, the furring strips might not be so beneficial, depending on the thickness of the material being used.
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Old 11-02-2021, 03:55 PM   #5
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Look into the 1/8th thick ceramic insulation talked about in this video.

https://youtu.be/hw1UpnSjLV0
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Old 11-02-2021, 04:14 PM   #6
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Look into the 1/8th thick ceramic insulation talked about in this video.

https://youtu.be/hw1UpnSjLV0

I didnt (can't currently) watch the video, but I did click through to the product website. They don't seem to give any technical data about it, an R-value or anything else, beyond vague and dubious claims in blog posts from customers ("space age", 1/8" insulation equivalent to 5-6" of foam, saved them over 28,000BTU/hr in heating, and maintained a warmer temp).


Do you know anywhere to find more reputable/technical info on what this form of insulation is and isn't?
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Old 11-02-2021, 04:57 PM   #7
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The couple in the video are just finishing up their third bus conversion and they live in them full time summer and winter as they travel around the US and Canada. Their second bus was spray foamed maybe 2.5 inches thick and they when they heard about that product, they remodeled their bus and added it as they put things back together and said it made a huge difference for them. Just throwing it out there just in case it might help someone, do your own research for sure.
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Old 11-03-2021, 10:08 AM   #8
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I'd like to see the tech specs as well.

Ceramics are great insulators, but they're typically brittle, which is why I didn't mention them for furring strips. Solve the brittle problem, like the ehp rollboard seems to do, and the issue goes away.
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Old 11-03-2021, 12:34 PM   #9
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I was just in the fire exit stairwell of a building yesterday and noticed the heads of the screws were discolored, like they rusted--but only on the exterior wall, not the other walls adjacent to conditioned living space.

My guess: lack of conditioned air in the stairwell and no air circulation causes localized condensation due to thermal bridging from the outside. The inside air temp follows the outside air temp but lags by some hours; when the outside air temp drops, the inside air temp follows but not before dropping some condensation on those screwheads.

My conclusion: don't underestimate the value of circulating the air inside the bus, especially behind cabinets and under mattresses.
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Old 11-03-2021, 01:23 PM   #10
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Insulation is an area with a lot of snake oil solutions and a lot of just general ignnorance/naivety (the popularity of reflectix in van builds being an example of this), and a lot of products that might work well in some certain context but not as a general insulator.


With that in mind, any insulator that doesn't provide technical details, or that sounds too good to be true, I generally assume is too good to be true, regardless of youtube/customer reviews, and that sort of thing. Placebo is real, and there are many people that rave about reflectix insulation in their van or skoolie, and many people on youtube/instragram/etc professing the miracles of nearly any product under the sun.


I'm not saying the couple in the video is wrong or that the product is not legit (it might be) but I think skepticism is a reasonable baseline assumption for a technical product without easily accessible technical details (most importantly R-Value), that is claimed to far exceed other more reputable products on the market. In some cases its true, in most cases its not.


However, it is possible that for the limited application of between the metal ribs and furring strips it might have some value, I don't know.


This is the website for anyone interested (looks like it was last updated in the late 90's)
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Old 11-03-2021, 02:42 PM   #11
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Originally Posted by dzl_ View Post
Insulation is an area with a lot of snake oil solutions and a lot of just general ignnorance/naivety (the popularity of reflectix in van builds being an example of this), and a lot of products that might work well in some certain context but not as a general insulator.


With that in mind, any insulator that doesn't provide technical details, or that sounds too good to be true, I generally assume is too good to be true, regardless of youtube/customer reviews, and that sort of thing. Placebo is real, and there are many people that rave about reflectix insulation in their van or skoolie, and many people on youtube/instragram/etc professing the miracles of nearly any product under the sun.


I'm not saying the couple in the video is wrong or that the product is not legit (it might be) but I think skepticism is a reasonable baseline assumption for a technical product without easily accessible technical details (most importantly R-Value), that is claimed to far exceed other more reputable products on the market. In some cases its true, in most cases its not.


However, it is possible that for the limited application of between the metal ribs and furring strips it might have some value, I don't know.


This is the website for anyone interested (looks like it was last updated in the late 90's)
I checked this stuff out. Agreed. No specifications, however generically it appears to be ceramic insulation blanket (silica-based instead of glass-based). It has wicked high temp ratings and is used in industrial applications mostly.

One product had some R-value information (more or less). A 1/8" mat has an R value of about 1.9 (pretty good, eh?), and at a half an inch, an R of about 7.6, at least at 400 degrees centigrade.

The big however, however, is that if these space-age blanket materials contain silica, even if they are considered non-toxic or inert, are not the kind of thing I'd want to breathe in under any circumstances.

A quick search on Amazon shows a vast selection of similar products advertising sound deadening and insulation barrier properties that are NOT made from this material.

I also question whether the improvements in interior temperature are all from the R value. This stuff is conformal, and that makes it as much of an infiltration barrier as an insulator. Meaning perhaps you'd get similar improvements to interior air temperature with an air infiltration barrier like Tyvek.

This one gets a no vote in my book.
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Old 11-03-2021, 03:14 PM   #12
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I checked this stuff out. Agreed. No specifications, however generically it appears to be ceramic insulation blanket (silica-based instead of glass-based). It has wicked high temp ratings and is used in industrial applications mostly.

One product had some R-value information (more or less). A 1/8" mat has an R value of about 1.9 (pretty good, eh?), and at a half an inch, an R of about 7.6, at least at 400 degrees centigrade.

The big however, however, is that if these space-age blanket materials contain silica, even if they are considered non-toxic or inert, are not the kind of thing I'd want to breathe in under any circumstances.

A quick search on Amazon shows a vast selection of similar products advertising sound deadening and insulation barrier properties that are NOT made from this material.

I also question whether the improvements in interior temperature are all from the R value. This stuff is conformal, and that makes it as much of an infiltration barrier as an insulator. Meaning perhaps you'd get similar improvements to interior air temperature with an air infiltration barrier like Tyvek.

This one gets a no vote in my book.

Thanks for the info and sharing your research/context, do you recall where you found the R-value info, I would be keen to look at it (and try to see how temperature affects it--I suspect this type of insulation is much more effective at high temp--but that is just speculation on my part based on the fact it is almost always used/marketed towards extreme temp applications, and seemingly not considered in other applications save for this one company that markets towards skoolies without any performance data). 7.6 per half inch would be great if accurate for the temperature range humans experience.
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Old 11-03-2021, 04:32 PM   #13
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Thanks for the info and sharing your research/context, do you recall where you found the R-value info, I would be keen to look at it (and try to see how temperature affects it--I suspect this type of insulation is much more effective at high temp--but that is just speculation on my part based on the fact it is almost always used/marketed towards extreme temp applications, and seemingly not considered in other applications save for this one company that markets towards skoolies without any performance data). 7.6 per half inch would be great if accurate for the temperature range humans experience.
I searched for 'silica in ceramic insulation material', which brought up a number of sites. Here's the one I took data from:

https://ceramicfiber.com/silica-blanket/

R value (or U value, or K per square meter or whatever) appears to be an inverse but linear relationship to temperature in the range they gave, 400-1000 degrees C but I doubt if that relationship holds up for human temps, say -20 to +20 C. My guess is a half inch of this stuff is good for an R value of about one. It may be space age material, but the laws of physics will still apply.
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Old 11-03-2021, 05:56 PM   #14
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I searched for 'silica in ceramic insulation material', which brought up a number of sites. Here's the one I took data from:

https://ceramicfiber.com/silica-blanket/

R value (or U value, or K per square meter or whatever) appears to be an inverse but linear relationship to temperature in the range they gave, 400-1000 degrees C but I doubt if that relationship holds up for human temps, say -20 to +20 C. My guess is a half inch of this stuff is good for an R value of about one. It may be space age material, but the laws of physics will still apply.

Okay, so I'm not sure if I did it right, but converting the W/mK to R-Value based on what I think the formula is (1 / W/mK) * thickness in meters) came out to an R-value of 0.048 for 1/8th inch, at 400*C (750*F) and as you noted this figure drops semi-consistently as temperature decreases, so at human temp levels I expect the value would be even lower. If this is in fact the case, any insulative benefits of 1/8" space age material would be negligible even in comparison to the furring strips themselves (pine is a bit over R1 per inch IIRC), so the 1/8" space age stuff would at best be 5% of the furring strips. (unless I totally bungled the math which is entirely possible).


On a (light hearted) side note, the term "space age" is getting fairly long in the tooth, considering that most people alive today were born well after the beginning of the 'space age' and most technology before or during the peak of the 'space age' would be considered archaic by today's standards.
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Old 11-03-2021, 07:05 PM   #15
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Okay, so I'm not sure if I did it right, but converting the W/mK to R-Value based on what I think the formula is (1 / W/mK) * thickness in meters) came out to an R-value of 0.048 for 1/8th inch, at 400*C (750*F) and as you noted this figure drops semi-consistently as temperature decreases, so at human temp levels I expect the value would be even lower. If this is in fact the case, any insulative benefits of 1/8" would be neglible even in comparison to the furring strips themselves (pine is a bit over R1 per inch IIRC), so the 1/8" space age stuff would at best be 5% of the furring strips. (unless I totally bungled the math which is entirely possible).
Yeah, kind of myth busted I would say. Just as effective, and cheaper, to glue moving blankets to the walls.

:-')
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Old 11-03-2021, 10:31 PM   #16
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Yeah, kind of myth busted I would say. Just as effective, and cheaper, to glue moving blankets to the walls.

:-')

If I ever do build a space-skoolie where I will need to re-enter earth's atmosphere at tens of thousands of meters per second and handle the thousands of degrees of heat generated, I will definitely revisit this, it might be a good choice.


On a more serious note, one place this type of insulation might have some value is in the context of woodstoves.
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Old 11-04-2021, 06:17 AM   #17
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If I ever do build a space-skoolie where I will need to re-enter earth's atmosphere at tens of thousands of meters per second and handle the thousands of degrees of heat generated, I will definitely revisit this, it might be a good choice.
Nah, Henry's Tropi-Cool is all you'd need - it's got ceramic beads in it!
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Old 11-04-2021, 03:11 PM   #18
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Nah, Henry's Tropi-Cool is all you'd need - it's got ceramic beads in it!
Where did you see Tropi-Cool has beads? It's 100% silicone.
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Old 11-04-2021, 07:16 PM   #19
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If I ever do build a space-skoolie where I will need to re-enter earth's atmosphere at tens of thousands of meters per second and handle the thousands of degrees of heat generated, I will definitely revisit this, it might be a good choice.


On a more serious note, one place this type of insulation might have some value is in the context of woodstoves.
Excellent point.

I keep shaking my head at those stove surrounds that don't have an air gap between the metal (or stone) shield and the surrounding combustibles; or no spark pan in front of the stove door.
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Old 11-04-2021, 09:35 PM   #20
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Excellent point.

I keep shaking my head at those stove surrounds that don't have an air gap between the metal (or stone) shield and the surrounding combustibles; or no spark pan in front of the stove door.

Yes looking at some builds, it becomes abundantly clear why insurance companies are reluctant to insure buses with woodstoves (or roof decks for that matter). Some people do it right, and put in the research and due diligence, but in so many cases you see a woodstove just plopped in there, barely secured (or in some cases not secured), with tiny airgaps and flammables around.
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