Roof Coating

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Roof Coating

January 31, 2014, 08:23:44 am

Well the snow at home then in the south kept me in Nac an extra week. While taking a picture of something on the roof we noticed big cracks and blisters. They were. Not up there last year but were there now. Brought it over to Xtreme who patched it up and we set an appointment for a couple months out. But the snow came and James was nice enough to fit us in. So, roof repaired and coated too. The coating has a summer insulation factor of R22. Putting stuff together today and leaving this afternoon. I will let you guys know this summer how the coating went. I hope it cuts down some heat. I thought about winter camping but usually go south and even in Nac we go snow and ice.

Re: Roof Coating

Reply #1 – January 31, 2014, 10:20:53 am

John, was the cracking and blister on the OEM roof or was it from a prior roof coating that might have failed? Safe travels home!

Re: Roof Coating

Reply #2 – January 31, 2014, 10:59:52 am

Quote from: John S – January 31, 2014, 08:23:44 am

The coating has a summer insulation factor of R22.

Sorry John, Steve did an engineering analysis on that roof coating. It's an "Effective" R-value, based on the reflectivity and color (white) compared to a non-white, non-reflective. It is not a true R-value. The true R-value at the typical application thickness is very small, about R 0.13

Below is the net of the analysis Steve did:

The most important thing that I found was they are being a bit misleading regarding the R19 "equivalence" claim. From the literature the THERMAL PROPERTIES of the material are: k(eqv) = 0.23 (Btu·in)/(hr·ft²·°F)

From this k(eqv) value we can calculate the true R value of the product as follows. Take the reciprocal of the k(eqv) value because the thermal resistance (R) is the reciprocal of thermal conductance (k). The equation is simply 1.0 / 0.23 --- this gives a value of 4.348. To this you multiply by the thickness of material being used, in this case 0.030 inches, to get an R insulation value of 0.130 thermal resistance, or R0.13.

R0.13 is a long way off from R19, which is where the equivalence claim comes in.

The test they did is essentially taking a piece of untreated metal, and one with the coating applied to one side, and place them both under a heat lamp. After some period of time, measure the temperature on the untreated backs of the samples, the treated sample will be much cooler than the untreated. The temperature delta of the two can be expressed as an R equivalence value, by asking, how much insulation would be required to reduce the heat gain through the un-coated sample to have the heat reduction of the coated sample. The answer is an assumption as to what the R-value is.

It's really no different than having two coaches in the sun, one white and one black, the white one will be cooler, but it has nothing to do with R value of the white paint, its simply more reflective than black. As an example here at Camp Foretravel there are three coaches facing the sun. I went and measured the temperature with an IR gun ... the white coach was 110, a light silver (mine) was 135, and the dark coach was a blistering 165. But the Rvalues of the walls and the paint are the same.

So I would not claim an Rvalue for the coating, it simply has a high reflectance value. I have no idea how much more reflective it is over a new white gel, or a oxidized gel coat, or a good white acrylic paint but I suspect it's minimal.

The question may be in how it holds up over time vs other reflective paints / coatings, its resistance to mold (stays white longer??), or its impact resistance? (hail) or even scratch resistance?. Would it hold up to being walked upon? My gut tells me any good cool white roof reflective coating (ppg) will be just as good.

If the coating really had an R-value of 22 at a 0.030" thickness, all the buildings in Texas would likely be coated with that stuff

.

Michelle

Re: Roof Coating

Reply #3 – January 31, 2014, 11:19:48 am

Michelle, that last sentence is the real story, and reality check-so to speak.
John H

Re: Roof Coating

Reply #4 – January 31, 2014, 11:37:58 am

Interesting application of R-value. Their R22 is not likely to help you much at night.

There is a word that aptly describes reflectivity: albedo. But it's mostly used by astronomers and - especially lately - meteorologists. Maybe it's time to put that word into the lexicon for buildings and vehicles. It's not just more descriptive but it has a well-developed measurement scale.

Craig

Re: Roof Coating

Reply #5 – January 31, 2014, 11:55:02 am

Yes I realize that it is not a true insulation but the reflective properties are important. I looked at both and decided on this one and we will see. It uses microspheres to help. Who knows if it is any better or not. I thought I would try it and see this summer if it makes a difference. The way we can test it is to get two coaches who have a painted roof and one with this coating and test the roof on the inside I would think. It was the OEM roof. Nothing had been done other than washing it from time to time. IT happened in a years time too. It was pretty ugly. We had 6 sections that had blisters and a bunch of pinholes that Rance used a Dremel tool to open up and patch. It looked like a boat that you sanded down to open the blisters. The coating is thicker than paint too so that is another reason I went with it. It will force any further outgasing downward and not up and blister the paint.

Re: Roof Coating

Reply #6 – January 31, 2014, 12:16:08 pm

Quote from: John S – January 31, 2014, 11:55:02 am

It uses microspheres to help. Who knows if it is any better or not.

Not in any significant way. WRT reflectivity we would suspect it to be about the same as any of the other white roof coatings/paints.

Just to give you an idea, here is Steve's analysis if the coating was the same material as what's known to be an uber-insulator, space shuttle tile:

I did some more digging around and found the k(eqv) value for a shuttle tile, it's 0.028 BTU/ft-hr-F (at 70 degrees). This is a factor of 10 better than the k(eqv) value for the spray on coating. However even using the R value of a space shuttle tile we would only get an R1 for .030" of material, the thickness of the applied coating.

Those tiles are also a special version of fused silica ceramic and are up to 5 inches thick. For more readily-available ceramics, like the microspheres in the spray coating, while good, look to provide negligible R values at just .030" thickness.

Re: Roof Coating

Reply #7 – January 31, 2014, 01:15:48 pm

The roof coating Xtreme put on our roof was less than 0.001", 10 mils, typical of most paint type coatings so even less R value. I know that Foretravel has been using a High Build coating like Rhino but even that was less than 0.030", 30 mils, as I recall and did not include any insulating particles.

Re: Roof Coating

Reply #8 – January 31, 2014, 02:22:38 pm

You could always duct tape some pink insulation down on the roof! Now that would be a sight!

Re: Roof Coating

Reply #9 – January 31, 2014, 08:11:52 pm

This coating looks like frosting on a cake rather than paint.

Re: Roof Coating

Reply #10 – January 31, 2014, 08:18:26 pm

Here is a picture. The summer will be a good test. The reason I chose this coating is that it is heavier and will help prevent future out gassing.

Re: Roof Coating

Reply #11 – January 31, 2014, 09:38:12 pm

Kent, I believe you are correct or very very close to it.
I was surprised......and yes, should have asked or done some research, but Xtreme did a One Coat paint job on my roof/with some 'shark' grit added for the non-skid effect. My brain from old days of painting would have 'required' a dust coat/layup #1 and #2 coats. However, the roof is not about looks, just performance..

I do trust these guys from Top down... at Xtreme.. good guys, good work ethic so I've got to feel, after questioning them that THEY are not going to risk 'anything' on just doing a One Coat paint job..unless they are absolutely correct.

Time will tell, but I will say, they know more than me, so I went for it. Hope all is well on your end...ron

Re: Roof Coating

Reply #12 – January 31, 2014, 10:03:20 pm

I am the second coach they used this coating on. It is much thicker than paint and Ron is right about time will tell. I talked to them about the options but with blistering they wanted a thicker coating than just paint. It should solve my issue after they fixed the spots permanently.

Re: Roof Coating

Reply #13 – January 31, 2014, 10:09:01 pm

Just as a point of perspective, we used to install 8 mils WFT of epoxy or urethane for an industrial floor that has forklift traffic on it. These floors would last at least 5 years with 24 hour use. Top quality urethane or epoxy coating is very durable and 3 mils on a coach roof should last 20 years and more. It will not bridge any substrate cracks. The thicker coatings, 30 mils or more, will provide some crack bridging but should not be necessary on our roofs unless there are structural or bonding problems. I hope this helps understand high grade coatings like those used on our coaches.

Re: Roof Coating

Reply #14 – January 31, 2014, 10:11:15 pm

I believe they put down a primer coat first. It took a full day to apply and dry. I was told the heavier coating will hopefully cause any further out gassing to go downward too.

Re: Roof Coating

Reply #15 – February 01, 2014, 10:37:15 am

Your right about that R-22 rating . If it were so , I'd paint the top of my head with it.

Brad Metzger

Re: Roof Coating

Reply #16 – February 01, 2014, 12:33:16 pm

It should be a permanent fix. The extra thickness and the reflective properties working together.

Re: Roof Coating

Reply #17 – February 01, 2014, 04:12:02 pm

Quote from: John S – January 31, 2014, 08:18:26 pm

Here is a picture. The summer will be a good test. The reason I chose this coating is that it is heavier and will help prevent future out gassing.

That coating looks very thick, John. It will be good to find out its performance over time. James just used the single stage roof coating on "Forrest" which is basically a painted on substrate with some anti skid feature to prevent fiberglass oxidation.

Re: Roof Coating

Reply #18 – February 01, 2014, 04:16:57 pm

Quote from: John S – January 31, 2014, 08:23:44 am

Well the snow at home then in the south kept me in Nac an extra week. While taking a picture of something on the roof we noticed big cracks and blisters. They were. Not up there last year but were there now. Brought it over to Xtreme who patched it up and we set an appointment for a couple months out. But the snow came and James was nice enough to fit us in. So, roof repaired and coated too. The coating has a summer insulation factor of R22. Putting stuff together today and leaving this afternoon. I will let you guys know this summer how the coating went. I hope it cuts down some heat. I thought about winter camping but usually go south and even in Nac we go snow and ice.

How did Xtreme patch the cracks? I have a couple of small cracks that need patching, and I am getting all sorts of opinions about how it should be done, ranging from self leveling calking ... to grind and fill with Bondo & glass fibers then gel coat ... to grind deeper and fill/patch with glass fiber mat and resin, then fill with Bondo and glass fibers, and finally paint. The biggest crack runs right across the center of the coach like a pencil line about 18 inches long and no deeper than the gel coat.

Re: Roof Coating

Reply #19 – February 01, 2014, 06:12:47 pm

It is determined by the crack. I had a bunch of listers that the gridded out to open and reglassed it. Some they dare melted out and put epoxy in then the heavy roof coating. James indicated it was not R22 really but worked like it in the summer. It is much thicker than paint or the coating FT uses as well. I liken it to frosting on the roof.

Re: Roof Coating

Reply #20 – February 01, 2014, 09:06:50 pm

John, Hope you are well and traveling safely.

MY coach was 'just' ahead of yours at Xtreme... to get the roof paint(Paint! One coat of Paint and some grit) and I'm befuddled now, learning there were options of roof coatings at Xtreme Paint and Graphics and would like to know why and what the differences are in the products they have in their arsenal and when was this info available?

I chose to redo my roof, basically to reduce chalking streaks on the sides of my coach and just bring it back to 'clean/safe' standards, but.... BUT if their is a thicker/and maybe better... coating that offered "SOMETHING" else, I'm surprised I and others were not offered this info.

I did the 'non-skid' part for safety, but at 175 lbs. I hopefully walking carefully will not do damage up there to the thin skin used up there.. however... Nothing too strong ever broke is an old saying, so with a roof coating, I'd add, nothing to good will fail..

Ok, I've spent my $ but would like to know more and hope to continue this thread.. Kent's ideas are inline with mine.

Did I just 'miss' this on this forum?

thanks for any reply... ron sheridan

Re: Roof Coating

Reply #21 – February 01, 2014, 11:05:03 pm

Personally I would have the max guard 29 either applied or reapplied. Something I am missing?

Bob

Re: Roof Coating

Reply #22 – February 02, 2014, 11:38:48 am

Ron, if you did not have cracks the paint is just as good. I asked why didn't you do The coach ahead of me. He did not need it. It costs a bit more too.

Re: Roof Coating

Reply #23 – February 02, 2014, 11:59:04 am

I have to do some surgery on the roof of 240 when the weather warms up as the Maual Sat dish that was on(now half removed) had been leaking and nothing done about it so the inside ceiling cloth has some nice rust stains around that area. The leaking had been happening for a while I guess as the fibreglass/gel layer is seperated for about a 2'x2' area so I will be cutting that all out and repairing what needs to be done. I will then used F matting and resin etc to repair area, sand, then coat with white Elastomeric Paint. I may sand the whole roof and paint it all, depends on what I see when doing it. $100 will repiar all roof as I have the matt and fibreglass resin and hardener and a litre of gel.
The inside ceiling I am fixing by making a panel of 1/4" sanded ply and glueing on the material that is coming to match original. It will go from cabinets one side to other and cover that stained section. I am also removing the Wineguard antenna as well like on our other coach.Should look fine.
John H

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