Declaring war on Interstate summer heat gain

[InterBlog]

Originally Posted by Mcrider

Why not try 3M™ Automotive Window Film Crystalline Series
....

I said WAR on summer heat gain. War entails strategic advances on multiple fronts. Maybe not all at the same time, because I'm just one warrior (presently with a sore back courtesy of yesterday's battle). But at this point, I have ruled nothing out. I haven't ruled window treatments in or out. I've not done any research yet.

[InterBlog]

Originally Posted by Troutboy

DuPont Tyvek Reflective Membrane..... google it, its breathable as well, and should fold thin. ...

I will check and see if this is available here. When I googled it, the first half dozen sites that pulled up were in the UK.

Radiant barriers are de rigueur in Texas attics, have been for more than a decade now. I've always wondered why nobody has developed an analogous product for walls. Figured it was because of the mode of operation - the attic barriers reflect heat back up into the roof sheathing, and I think they might need air space below them (the open attic) to properly perform this function. No such air space in walls.

[InterBlog]

Originally Posted by FlyFishinRVr

How about something a little crazy like coating the roof with thermoelectric paint and make use of all that waste heat? In theory the paint would absorb a bunch of the heat and a quick back-of-the-napkin calculation says you'd get back as much as 600W of electricity (depending on the output power density of the paint used and how much of the roof you cover). The only fly in the chardonnay is availability and cost of the paint, which might be a bit high given the technology is still relatively new, but who knows, maybe you could be a test case for one of the manufacturers.

Anywho, thought I'd toss that out there....

We are trying to make our Interstate last another 10 years. We figure that, in 10 years, the tech will have advanced significantly on multiple fronts, and then it will be time to either buy or build its successor. Maybe something like that will be an attainable reality in another 10 years - who knows.

[Wayne&Sam]

Maybe it helps reflect some heat on a roof, but don't try this.

[InterBlog]

Originally Posted by Wayne&Sam

Maybe it helps reflect some heat on a roof, but don't try this.

Now you can see why I bought an infrared thermometer for this occasion. I, too, have been skeptical of these claims - which are not all consistent, by the way. This summary below appears on NASA's own website. It says "the coatings reduce temperature". Well, that's rather nonspecific. By how much? By an amount that makes the product worth the time and money? Or is it just greenwashing?

https://ntrs.nasa.gov/archive/nasa/c...0030099691.pdf

I couldn't find any confirmation either way, that yes it is worth it, or no, it's hype. There are anecdotal reports from RV, trailer, and van owners who claim that products the same as, or similar to, what I'm using make a very noticeable improvement. But could that be a placebo effect?

I will say that our first front-line battle against heat rejection came about two years ago after we discovered no insulation above the headliner of the cab. On the underside of that portion of the roof, we placed a layer of Dynamat and overtopped that with a layer of radiant barrier (because there is an air gap in that location, much like a stick-and-brick attic). I didn't own an infrared thermometer at that time we did that job, so I have no actual before-and-after numbers. But I'd swear that it made a significant difference. I put my hand on the headliner today and it feels cool to the touch, and I now know that the nose cap directly above it is running upwards of 140 F.

[LB_3]

As the article mentioned, no surface coating just a few mills thick (regardless of marketing hype or exotic additives) will provide a significant R value. Almost all the value is in the reflectance and this paint at first look is really really white. Will it stay that way with pollen and dust on it? Hopefully better than the flat gray roof paint. What I can't tell looking at it is what its reflectance is in the infrared spectrum.

Hopefully the relative ease of application, as compared to removing the solar/AC and prepping, masking, and spraying a white automotive paint, provides some meaningful heat reduction and justifies the effort going into InterBlog's experiment.

[Troutboy]

I think you are right about that tyvek reflex, but if you really wanted it, i was able to find a few stores online that you could order it, for about $200 USA for a roll that would likely work on the windows in your AI.

[InterBlog]

Originally Posted by Troutboy

I think you are right about that tyvek reflex, but if you really wanted it, i was able to find a few stores online that you could order it, for about $200 USA for a roll that would likely work on the windows in your AI.

There must be an explanation for that. Why would such a product be for sale in the UK where there's nowhere near the same need for radiant barriers, relative to a place like the deep south of the U.S., where we live and die by radiant barriers? (awkward sentence)

$200 vs. the $20 I paid to make my own... I'd have to be really convinced that it would be an improvement.

[InterBlog]

On "relative ease of application", count on about 8 hours of strenuous work spread across four sessions carefully timed. One 4-hour session for prep and primer, and each subsequent application takes about 1 hour... and I can see that I'll need a minimum of 3 coats of the Bus Kote... I put the first coat on late yesterday afternoon and then we drove it back to the storage unit so that the dew would not set on it.

But if I were y'all, I'd wait to see how my project performs before I try the same application. As I noted to LB_3 yesterday, not every uncharted Interstate DIY project turns out to be a home run - we know this all too well. I don't have a feel for this one yet.

On the issue of reflectance, I have no feel for that either. I do seem to be creating the highest-albedo surface in the known universe ("white" doesn't come close to describing it). Now, how might that compare to, say, the roof of a white FEDEX Sprinter with standard automotive paint? No idea. I have visions of ambushing our neighborhood FEDEX driver, yelling, "Wait! Wait!" and slapping a ladder up against the side of his truck so that I can shoot a temp reading on HIS roof to see how it compares to ours measured at the same time.

[RandyNH]

Right there is a good reason for being a FedEx driver and not a UPS driver.

[InterBlog]

Originally Posted by RandyNH

Right there is a good reason for being a FedEx driver and not a UPS driver.

In greater Houston, UPS drivers almost always drive with their cab doors open. Even on the freeway. FEDEX typically does not.

[pteck]

Just a thought. Have you looked into solar screen material? It's incredibly effective for homes and I wonder if may be a better looking option?

[InterBlog]

That's one of the reasons why I hatched this thread - to see if other people come forward with alternative ideas.

Unless I'm missing something major, this is largely uncharted territory.

It just boggles my mind that people use Class Bs of all types, many different platforms, plus DIY converted vans and trademan customizations, delivery vehicles, etc. .... lots and lots of these vehicles being used (I can't come up with a defensible estimate, but given that we have 254 million total motor vehicles on the road in America, I'd bet the cargo / conversion / trades / delivery / Class B van subset exceeds 10 million), and nobody has addressed this heat gain issue in a way that clearly trumps other options.

In other words, you'd think that someone woulda worked it out by this time. Every van used for every purpose is going to be difficult to cool by virtue of interior volume. A 146 degree F van roof on an 85 degree day in March in Houston - that's about on par with what much of the rest of the country experiences in mid-summer. Why hasn't anyone done anything about it and come up with a clear solution? I don't know. There's certainly a market for it.

Rant concluded. For now.

[InterBlog]

The project continues. This is what it looks like with primer plus a single coat of Bus Kote (it still needs two more coats). The weather has not been cooperating these past few days and thus it has slowed me down.



These conditions are not directly matching my initial photo where I had 146 degrees F, so the variables aren't yet held as constant as possible. Time of day is about the same, sun angle is actually a bit higher in this 108 F pic, but air temp is about 75 instead of 85. However, the other day when I took the 146 F pic, there was a stiff breeze blowing across this roof, providing some degree of air cooling (however small). In this 108 F pic there is nothing - the air is basically standing still at this location right now.

I will get a pic that more closely approximates the initial 146 F pic environmental conditions, but ^^ there's that much for now.

OMG, it is whiter than white. When I view it, I feel like those guys in Raiders of the Lost Ark where their faces melt off. Seriously. It's literally painful to look at it.

[73shark]

Wouldn't a more meaningful data point be the inside surface temperature as a measure of how effective any exterior coating is?

[InterBlog]

Probably, but that was just an interim report. Qualitatively, the interior ceiling felt much cooler, which it would naturally have to, because the interior ceiling previously was at 110 F and if the exterior of the same spot is subsequently at 108 F, it's hard to imagine what could possibly make the interior as hot as it had been during the initial measurement. When I get done with the full job, then I'll start making more careful measurements.

[KSA63]

Originally Posted by InterBlog

That's one of the reasons why I hatched this thread - to see if other people come forward with alternative ideas.



Unless I'm missing something major, this is largely uncharted territory.



It just boggles my mind that people use Class Bs of all types, many different platforms, plus DIY converted vans and trademan customizations, delivery vehicles, etc. .... lots and lots of these vehicles being used (I can't come up with a defensible estimate, but given that we have 254 million total motor vehicles on the road in America, I'd bet the cargo / conversion / trades / delivery / Class B van subset exceeds 10 million), and nobody has addressed this heat gain issue in a way that clearly trumps other options.



In other words, you'd think that someone woulda worked it out by this time. Every van used for every purpose is going to be difficult to cool by virtue of interior volume. A 146 degree F van roof on an 85 degree day in March in Houston - that's about on par with what much of the rest of the country experiences in mid-summer. Why hasn't anyone done anything about it and come up with a clear solution? I don't know. There's certainly a market for it.



Rant concluded. For now.

There is a company in Australia called Kimberley that makes caravans for the Australian market. If they could be purchased and serviced easily in NA I think that I may have gone that direction. Anyways, they have made some serious reductions in heat buildup with their tropical roof system. Have a look here...

http://info.kimberleykruiser.com/wor...tropical-roof/

Kevin

[UKDUDE]

Originally Posted by KSA63

There is a company in Australia called Kimberley that makes caravans for the Australian market. If they could be purchased and serviced easily in NA I think that I may have gone that direction. Anyways, they have made some serious reductions in heat buildup with their tropical roof system. Have a look here...

http://info.kimberleykruiser.com/wor...tropical-roof/

Kevin

That tropical roof reminds me of many years ago (in the 60's and 70's) when I was living in Africa where my father worked at that time: all the Land Rovers were equipped with a factory tropical roof; it was essentially a metal sheet suspended about 3/4" over the standard roof and designed to keep the heat off the main roof and permit a flow of air between them.
I suspect it wasn't that effective since it was no longer an option after the 80's.

[FlyFishinRVr]

Originally Posted by InterBlog

That's one of the reasons why I hatched this thread - to see if other people come forward with alternative ideas.

Unless I'm missing something major, this is largely uncharted territory.

It just boggles my mind that people use Class Bs of all types, many different platforms, plus DIY converted vans and trademan customizations, delivery vehicles, etc. .... lots and lots of these vehicles being used (I can't come up with a defensible estimate, but given that we have 254 million total motor vehicles on the road in America, I'd bet the cargo / conversion / trades / delivery / Class B van subset exceeds 10 million), and nobody has addressed this heat gain issue in a way that clearly trumps other options.

In other words, you'd think that someone woulda worked it out by this time. Every van used for every purpose is going to be difficult to cool by virtue of interior volume. A 146 degree F van roof on an 85 degree day in March in Houston - that's about on par with what much of the rest of the country experiences in mid-summer. Why hasn't anyone done anything about it and come up with a clear solution? I don't know. There's certainly a market for it.

Rant concluded. For now.

I don't know, it seems to me AS is doing a pretty decent job of insulating these rigs. They're using 3 1/2" batt in the walls and ceiling which, given the small space, seems pretty reasonable. Even a coach like the Leisure Travel vans only have a R 9 rated ceiling, and they're made in Canada for an arguably harsher environment (primarily cold though, not heat). I'm just not sure what more AS can do given the trade-offs involved (weight, storage space, living space, etc)......

As for the delivery vehicles, tradesmen, etc., most have nothing in the ceiling, but they don't live in their vans. They are either always moving (delivery) or drive to a job site and work outdoors. As a result I just don't think it's a problem for them. They're also up in the cab, so while they're driving they can make use of the dash AC.

For the DIY'ers, I've seen some builds put reflective insulation in the ceiling or spray in some expanding foam here and there, but neither of those solutions are going to be as good as what we already have. Also, most of the DIY full-timers I read about travel north in the summer to get out of the heat and head back south in the winter.

Maybe you just need to work WITH mother nature rather than fight her......

[LB_3]

Not being retired it's hard for us to follow the weather.

But the reason industry isn't doing a better job is because the technology doesn't exist. If it did there wouldn't be so many snake oil salesman marketing magic paints. The best insulating technology today is aerogel but it's no better than styrofoam after a few years when the vacuum leaks out of the Mylar bags.