Using Kool Seal on the Inside of the Outside?

[aluminitus]

I'm not sure if this is in the right category, but here goes.

After reading Darkspeed's account of painting the interior of his Airstream's outer skin with ceramic insulation, I had a case of the green-eyed gazunga and wanted to do the same on mine. Then I found a thread about painting the roof with Kool-seal to make the roof bearable to sit on. It occurred to me that maybe I could paint the inside of the outside skin (clear as mud, right?) with Kool-seal and it would have the same effect, namely causing the skin to stay cool and better insulate the Airstream. Has anybody tried this? Do you suppose it would work?

[perryg114]

It would provide some insulation value but it is not going to reject heat like it would on the top. Cool seal reflects visible light back where it came from and the heat along with it. It will have some R-value but it won't reflect heat because it has bad IR reflectivity. It reflects visible light not heat energy or IR. If you want to reflect heat energy you need something like aluminum. You need a radiation barrier which looks like shinny bubble wrap.

What happens is the roof absorbs sunlight and converts it into heat. That heat goes right through the skin. You can do one or both of two things. You can reflect it back to the skin and hopefully get it back out of the trailer or you can insulate and reduce the transmission of heat to the inner skin. You can use a combination of both of these things. Actually polishing the roof is going to be as effective as putting cool seal up there; both surfaces reflect visible light well. The cool seal will mold and mildew and unless you bleach it often it will lose its effectiveness. Cool seal might be good on the inside to seal off leaks. You would need to strip the inside skin of all glue to do this.

I don't know what Darkspeed is using and how tough a coating it is. Ceramics in general tend to crack. I expect the value of his coating is that is does not conduct heat well. I would hope it has some sort of rubberized binder so it does not crack and peel off. Ceramic has been turned into a weasel sales word. Paint by nature is not pure ceramic. It has other stuff in it. Just about all paints have ceramic in them because the pigments are made of metal oxides. Does the fact that paint has ceramic in it mean that it just like a ceramic, no! There are some paints that have ceramic binders but they are brittle.

Perry

[DaveFL]

I would go with the bubble wrap, but one better would be the one HD or Ace has on rolls, both sides have a shiny reflective surface. Something like 3M spray adhesive should hold it in place. This should reduce the condensation that will occur inside your inner walls due to less temp difference.

[marzboy]

If I were you I would go with Prodex. It is a closed cell foam in cased in foil. The problem with air bubble insulation is it pops in high heat and looses its R value. I have read Darkspeeds thread and the guy is an evil genius. But I am not that tec to spray a thick ceramic paint. I think it is easier to tape in Prodex. It doesn't off gas formaldehyde it is Ozone friendly a very green product. Check it out, it is going to be my next big task after I get my shell leak proof!

[aluminitus]

So I am ordering 5 gal of HSC (they no longer make HSC-1500) in the morning, which will probably get painted on instead of sprayed. It won't be pretty, but it's getting covered anyway. Then the wiring, then a layer of reflectex (so hopefully the HSC will block enough heat so the bubble insulation won't pop). No way no how am I going back to that yellow insulation!

[marzboy]

Originally Posted by aluminitus

So I am ordering 5 gal of HSC (they no longer make HSC-1500) in the morning, which will probably get painted on instead of sprayed. It won't be pretty, but it's getting covered anyway. Then the wiring, then a layer of reflectex (so hopefully the HSC will block enough heat so the bubble insulation won't pop). No way no how am I going back to that yellow insulation!

I'm tellin you check out the Prodex it is pretty legit stuff. I have two rolls in my garage and it looks really quality. The reflectex is super flimsy and I doubt it would be very good at insulating anything let alone sound proofing. I got my Prodex 1/2 off on sale! Just sayin....

[perryg114]

Remember that the Prodex and other radiation barriers only work as long at the reflective surfaces stay clean and intact. Water will corrode the coating and dirt and any other contaminants will degrade the reflectance of the material over time. I think that combining Prodex with some sort of foam is best. This is why I use RMAX foam that is R-3.2 for 1/2" and I use two of these in a wall. It has aluminum on both sides. One side if white and the other side is shinney. I would put the aluminum on the first layer facing the outside wall and the aluminum facing the inside wall on the second layer. So you have R-6.4 plus. I think the R value is just the foam thickness and the aluminum is going to get you a little more. You can put Prodex as a 3rd layer if there is enough room.

Perry

[FC7039]

Originally Posted by aluminitus

So I am ordering 5 gal of HSC (they no longer make HSC-1500) in the morning, which will probably get painted on instead of sprayed. It won't be pretty, but it's getting covered anyway. Then the wiring, then a layer of reflectex (so hopefully the HSC will block enough heat so the bubble insulation won't pop). No way no how am I going back to that yellow insulation!

Do you plan on removing the ribs so that the HSC gets under them as a thermal break?

[marzboy]

Originally Posted by perryg114

Remember that the Prodex and other radiation barriers only work as long at the reflective surfaces stay clean and intact. Water will corrode the coating and dirt and any other contaminants will degrade the reflectance of the material over time. I think that combining Prodex with some sort of foam is best. This is why I use RMAX foam that is R-3.2 for 1/2" and I use two of these in a wall. It has aluminum on both sides. One side if white and the other side is shinney. I would put the aluminum on the first layer facing the outside wall and the aluminum facing the inside wall on the second layer. So you have R-6.4 plus. I think the R value is just the foam thickness and the aluminum is going to get you a little more. You can put Prodex as a 3rd layer if there is enough room.

Perry

Wouldn't that be a bit squeaky? I plan on cutting up strips of foam (RMax) to create air pockets.
Sorry aluminitus if I hijacked your thread

[perryg114]

Is all the old adhesive off the inside walls? If not nothing will stick.

Perry

[aluminitus]

Marzboy- I will definitely have to check Prodex out. Does it claim to work as sound proofing?

FC7039 - They way I understand it, heat would go through the (exterior) skin, into the ribs and then into the interior skin. If I just paint the exterior skin and all of the ribs, the heat will be stopped from transferring to the interior skin. That way, I won't have to remove the ribs to paint behind them.

Guess what arrived today!

[FC7039]

I have been running test. A youtube video to follow (if I can figure it out).

So far I have only used a 10 X 10 X 1 1/2 box made of two skins and the outside edges of 1 X 2 (wood as to not be a good thermal conductor) to represent the the monocoque of the trailer. You will see all in the video. Next round I will rivet in a "rib" to test how this conduction affects heat transfer from outer to inner skin.

I used a shop light as a heat source. The light bulb could heat the outer skin to 200 degrees.

I used a control (empty box) and a test.

These are the preliminary findings.

Insulation - control temp - test temp
1. one layer bubble foil with foam offsets - 108 - 94
2. commercial radiant barrier, think foil - 102 - 98
3. fiberglass - 104 - 96
4. HSC - 104 - 116

I ran the test for two hours and there was little difference from hour 1 to 2.

I suspect the difference in the control between test may be the ambient temperature or the first as test the bulbs were new. So use differences in each test.

Thoughts.
Test 4. The outside skin does not radiate heat that well. With HSC, it radiats the heat better than without. This might do better with some other insulation to block the radiant heat from outer to inner.

Test 1,3, with the bubble foil I sealed it with foil tape it did a little better than fiberglass, not taped but fully filling the space.

I am thinking that it is better to not put insulation against the outer skin to prevent conduction but to have it set away with foam blocks and fill the rest of the space with insulation. These test will follow along with test with a rib.

The HSC's value may be as a thermal break, but it does not work against the outer skin. I suspect against the inner skin it will allow any radiat heat better than aluminum.

I plan to repeat the test with ribs and to also test hsc with insulation and use multiple layers of bubble foil.

If there is any test you want me to try, please let me know.

[aluminitus]

FC7039 - I am definitely going to have to see a video of this! Are you saying that HSC would work better painted on the (non-showing side of the) interior skin? How would HSC painted on the inside of the exterior skin (and ribs) work with Prodex (or some other bubble insulation), maybe separated by foam blocks? Also, did HSC actually make the temperature rise between the control and test?

[FC7039]

Originally Posted by aluminitus

FC7039 - I am definitely going to have to see a video of this! Are you saying that HSC would work better painted on the (non-showing side of the) interior skin? How would HSC painted on the inside of the exterior skin (and ribs) work with Prodex (or some other bubble insulation), maybe separated by foam blocks? Also, did HSC actually make the temperature rise between the control and test?

Working on the video now (sorry for my poor youtube skills).

My take is, that clean aluminum does not radiat heat very well. It does conduct heat just fine. Painted, it radiates much better than if bare.

Hope to have the youtube up tonight.

Gene

[FC7039]

My first attempt (ever) at a youtube upload. The videois streched. The test pieces are square.

Airstream Insulation Test 1

[FC7039]

Originally Posted by aluminitus

FC7039 - I am definitely going to have to see a video of this! Are you saying that HSC would work better painted on the (non-showing side of the) interior skin? How would HSC painted on the inside of the exterior skin (and ribs) work with Prodex (or some other bubble insulation), maybe separated by foam blocks? Also, did HSC actually make the temperature rise between the control and test?

My ramblings were confusing.

Heat from the outer skin can transfer to the inner skin via conduction, convection and radiate. Aluminum does not emit radiant heat well. With a layer of HSC, this negates the aluminum and the white paint radiates the heat.


It is my understanding that while not radiating heat well, aluminum also does not accept radiant heat well. So painting either of the inner sides of the two skins defeats aluminum’s properties.

I think the best hope for HSC will be as a thermal break painted between the ribs and skins. Further test are needed.

The control is bare aluminum. It does not radiate or accept radiant heat well. Most heat transfers via convection/conduction. The HSC allowed more radiant heat to transfer, hence the elevated temp in that test. I was not expecting this but after I thought about it, it makes sense.

[marzboy]

Originally Posted by aluminitus

Marzboy- I will definitely have to check Prodex out. Does it claim to work as sound proofing?

FC7039 - They way I understand it, heat would go through the (exterior) skin, into the ribs and then into the interior skin. If I just paint the exterior skin and all of the ribs, the heat will be stopped from transferring to the interior skin. That way, I won't have to remove the ribs to paint behind them.

Guess what arrived today!

I believe it does help with sound dampening

[aluminitus]

Ugh. So I bought myself a very expensive bucket of white paste
Do you think it could be useful at all? Or should I ship it back?

[marzboy]

Originally Posted by aluminitus

Ugh. So I bought myself a very expensive bucket of white paste
Do you think it could be useful at all? Or should I ship it back?

You might as well use it. I dont think it would hurt. Besides, wont it help with waterproofing? Believe me when it comes to the many projects try not to over think things. There are many phases to these projects. It can make you a little crazy if you let it.

[aluminitus]

If I use it, won't it actually make the trailer hotter than having no insulation at all? A million thanks to FC7039 for performing the test, even though the conclusions made me grumpy