Declaring war on Interstate summer heat gain

[FlyFishinRVr]

Originally Posted by 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.

Then I guess "brute forcing" a solution is your only choice. Since you're already doing the Lithium/Solar thing, maybe you can replace the existing rooftop AC with a DC AC unit and run it off the new batteries: http://www.guchen.com/mini-bus-van-a...s-ac-unit.html

90A gets you 34,000 BTU's of cooling goodness, which in a coach the size of the Interstate should be able to blow snow on you in July....even in Houston.

[InterBlog]

For people who have not lived in the deep south, it can be difficult to imagine what we are up against here, and how motivated that can make us to identify workarounds and countermeasures to heat. Even modest gains can lead to big improvements in quality of life.

I mentioned on an unrelated previous thread that the new Honeywell digital thermostat we installed in our Interstate (blog post here) tops out at 99 degrees - it's incapable of displaying triple digits. How do I know this? Because exceeding 99 degrees is a routine event for us. I would like to see someone get to the point of experiencing 107 degrees inside their Interstate, which I have done, and say to themselves, "Well, I'm not really interested in trying to determine how I might minimize the heat being conducted through my roof." I predict that this sentiment simply wouldn't be generated in the face of that actual 107-degree experience.

We are not retired, don't have the freedom to follow the weather, and we've found that, even with traveling to cooler locations, we're still potentially looking at days and days on the road driving through blistering conditions before we ever reach, or return from, any coolness. This happened last summer when we first hit 95 degrees prior to exiting Maine, as we were driving back south from Nova Scotia. The entire Shenandoah Valley was around 100 degrees prior to sunset and I don't think it fell below 80 degrees overnight. These are harsh conditions for the type of boondocking we do.

I also threw this roof question onto Instagram with its 1.2 million uses of the hashtag #vanlife, and with its worldwide abundance and diversity of van DIYers. The only person to respond to me so far is James Wong, the same van builder who applied Bus Kote to his own 2006 T1N Sprinter, which I had read about on Sprinter Forum. It is now 41 weeks since he initially published his roof coating description and I was able to back-tag him and ask him how it's standing up so far, explaining that I was nervous about applying a latex product over automotive sheet metal, nervous about how that product might age over time. So I'm awaiting his feedback on that point.

[InterBlog]

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

I like it, and it speaks to two related issues - minimizing the absorption of incident energy, and also the potential for the solar panels to actually amplify roof heat gain rather than shading the roof, depending on how they were installed.

Thus far, I've measured our solar panels topping out between 135 F and 140 F - same temp I measured for the untreated roof itself. But here's the thing in our case - our solar panels are vaulted above our coach a/c unit, and surrounded by a big air gap at every point. As such, their effective surface area to volume ratio is enormous, to the point where I suspect air cooling is a significant controlling factor on how hot they can become.

In other words, even though they are clearly (and by design) absorbing more incident energy than the roof, they are also cooling more efficiently, to the point where they ended up sustaining about the same temperature.

Now, if someone were to instead plaster solar panels to their roof, I could believe that it might amplify heat gain depending on how it was done. It makes intuitive sense - black objects re-radiating in significant measure through that to which they are in direct mass-to-mass contact.

Something I noticed yesterday after applying my second Bus Kote layer - a stronger interior heat gradient from nose to tail. This is just a qualitative rather than semi-quantitative observation, but the front of our Interstate was about 10 degrees warmer than the tail. With the roof reflectance clearly improved to some degree, the windshield steps up to become much more conspicuous in the fraction of the total heat that is coming in by way of it. Even with the Heatshield interior window reflector in place, this difference was obvious to me. I may have to capitulate and create a cab isolation curtain, which I did not initially want to do. James of The Fit RV did that in part because of the difficulty in maintaining climate control without it. The windshield remains a big problem area even with a commercial covering being used.

Let me close this response with a quote from that website: "When Kimberley developed the tropical roof for their off road camper trailer, the drop in temperature inside the camper trailer tent was a staggering 25%."

[InterBlog]

I've learned that the performance of my little hand-held infrared thermometer gizmo starts breaking down as it strongly overheats (it's dark gray and black). It's a bit like my iPhone - I've taken it on outdoor job assignments only to have it shut itself down from overheating just because the Texas sun was shining on it for a few minutes. When the thermometer starts to overheat, I have to bring it back into the air conditioning for about 10 minutes to allow to cool sufficiently. Then go out and quickly take measurements so that they will have a measure of relative consistency, at least.

Anyway, today's conditions are harsher than when I took my first measurements. We had a front come through producing much drier air and the sun intensity and UV index are off the charts today, vs. partly cloudy when I made my original measurements.

Pre-coat: 146 F roof, 110 F internal ceiling temp
Post-coat: 112 F roof, 97 F internal ceiling temp

Same time of day, same sun angle, same ambient air temp, same general wind conditions, same parking spot. The only real environmental differences are no clouds whatsoever, less haze, and stronger sun today vs. originally.

[InterBlog]

Do any of you folks have middle-school-aged children or grandchildren who are serious Science Fair competitors? Because the more I noodle on this roof issue, the more my mind sees a home-run winning project, probably best suited to grades 5, 6, or 7 because, by the time they get into grade 8, the judges are really looking for evidence of impending transition to a high-school level of sophistication.

I know what of I speak. My daughter was a four-time Science Fair medalist in our NASA Johnson Space Center-rich district of 38,000 kids (i.e., the competition was intense), and in her last year of participation, was also a regional trophy winner (the region draws competitors from a pool of about 1 million school children). I was her coach on each project.

Anyway, I finished up my roof job yesterday and have this blog post below to show for it.

I caution readers that, although the initial results seem promising, we do not yet have any idea of how this type of application will either wash or wear, and those two considerations weigh heavily on the conclusion of whether it’s ultimately worth doing. Undoubtedly, I’ll have more to say about those things as we go forward and gain lessons learned.

ADDING A REFLECTIVE ROOF COATING TO AN AIRSTREAM INTERSTATE

[Wayne&Sam]

As an aside, nearly 50 years ago I owned a Land Rover Series 2A which was a Safari model. That meant it was designed for hot conditions- it didn't even have a heater in it.

The roof had an additional layer of aluminum on spacers that gave a couple of inches of air space between it and the real roof. So the top layer would heat up and lots of air flowed between it and the real roof. It kept the vehicle noticeably cooler.

[InterBlog]

^^Based on the sum total of what I know at this moment, that's probably the approach for which I would advocate if my husband and I were to design and build our own rig.

However I'd make such a cover easily removable and I'd probably put a layer of some elastomeric akin to Bus Kote on the original roof to boot.

The reason is because, as Class B DIYers, we are always on that danged roof for one project or another, always tinkering with something. We wouldn't be able to sit or stand on an aluminum cover like we do on an OEM roof.

I'm victorious like, YES!! because I can finally sit my bare thighs (short gym shorts) on that danged roof while doing other projects unrelated to the roof coating itself, without having those thighs sear like a pair of steaks on a grill. There's real danger in working on an Interstate roof - I like to keep as much of my corpse in contact with it as possible to minimize the chances of an accident. Bare feet and bare legs work in this regard - there's immediacy of sensation if slipping seems imminent. So if we had an aluminum reflector, I'd need to be able to remove it routinely for this reason.

[73shark]

Have you considered using 3M Crystalline film on all of the glass including W/S? It blocks up to 97% of the incident IR. It is expensive.

Considering using on my Transit if the price doesn't get silly.

[LB_3]

Originally Posted by 73shark

Have you considered using 3M Crystalline film on all of the glass including W/S? It blocks up to 97% of the incident IR. It is expensive.

Considering using on my Transit if the price doesn't get silly.

I'm thinking about it. May try it on my car first but being 12 years old, I'm not sure how much longer I will have it, particularly if Tesla doesn't screw up the Model 3.

[InterBlog]

(1) Anything we put on our windows would need to be almost clear, not tinted (I'm visually challenged). It looks like they do offer that product in a near-clear version.

(2) It's pricey but not obscene, if what I'm seeing on the internet is correct. I'd be willing to try it if I could be convinced it wouldn't degrade like most of the films I've seen.

LB_3 has a tint on his daily driver and it's gross. He bought the car used so he's not responsible for picking the tint, but it demonstrates absolutely everything that's bad about window films. Bad color, bad visual distortion, and it doesn't seem to stop a bit of heat. It just makes the windows look like someone threw up on them.

LB_3's car is a decade old with crappy window film already on it. My car is only six years old, but courtesy of Houston's freeways and the endless kicking up of rocks, I have four different splits in my existing windshield such that it's not worth investing in it. Neither is a good contender for experimentation. We'll have to noodle on this one.

[73shark]

Sounds like whoever did his car didn't know what they were doing. The only thing that happens to properly installed tint film as it ages is a very slight fading. Of course that assumes they used a good film to begin with. Cheap film turns purple as it ages and a bad install looks blotchy w/ a lot of trapped air.

You can get the 3M Crystalline as clear as 90% which should be almost imperceptible.

[Pahaska]

Is the 3M Crystalline installed inside or outside? I can't tell from the website. It is pretty hard to get at all of the interior glass in my IA. Much of it is covered with closeouts and much is blocked by the interior panels.

[InterBlog]

I had the same question given that I hadn't researched it thoroughly. Most films are applied on the interior surfaces, so I was assuming inside, but the websites didn't say.

[73shark]

Inside

[InterBlog]

We've identified a trusted local installer for window film, but I decided I won't proceed until I can see an example of that particular 3M product, the Crystalline CR 90, installed on a vehicle. I want to evaluate the quality of it in advance, if we are going to pay for such a relatively expensive job.

Next question becomes, how to find such an example?

In Houston, the answer is often tamales, our universal currency. When I get sufficient time available to me, I'll ask the installer and/or I'll throw that question onto our local Facebook Moms group (something like 12,000 group members). Let me see your CR 90 application and I will bring you some tamales for your trouble.

[InterBlog]

Interesting anonymous anecdote to fall out of my social media inquiries:

One of our large public transportation entities reportedly started using 3M Crystalline CR90 about 5 months ago. They did this despite the cost after they independently studied it and found that it performed as advertised. There are strict limitations on window films that can be placed on commercial vehicles that are deployed in the public service as transportation vehicles. Yet these drivers face the same issue that we do as Class B owners - they are routinely driving through a deep-south inferno in big vehicle cabs that let in an excessive amount of heat.

Apparently the drivers are quite favorable toward the product. As the responder noted to me, "[Nobody] has complained about [the product], and [these drivers] complain about *everything*."

[Boxster1971]

I recently had both driver and passenger front windows tinted with a product that competes with 3M. It was Formula One Pinnacle 40% Gray. It is a very close match to the color of the other rear tinting on my Interstate, just a bit lighter to stay legal in Maryland.

On my recent trip to California the side window tinting made a big different in driver and passenger comfort while driving in the bright sun. The true test will come this summer on my next road trip.

[InterBlog]

New Class B market entrant. You know that this statement is going to drive me bonkers until I manage to find out what they are applying, and how they are applying it.

[Mattirs]

Tin foil and duct tape

[TayaraTravel]

Originally Posted by InterBlog

We've identified a trusted local installer for window film, but I decided I won't proceed until I can see an example of that particular 3M product, the Crystalline CR 90, installed on a vehicle. I want to evaluate the quality of it in advance, if we are going to pay for such a relatively expensive job.

Next question becomes, how to find such an example? ...

We will be the guinea pig. We've decided to install 3M 70 on windshield ($548) and 3M40 on driver + passenger side windows ($598). Our installer is Midtown Motor Trends. Price is high, but the labor alone is substantial: 2 people most of one day. The windshield is too big for a single application, so we are getting s "sun visor" upper band. Probably getting it done late next week.