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Old 03-26-2017, 02:16 PM   #1
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Declaring war on Interstate summer heat gain

I'm hatching a new thread on this topic because most of the previous discussions have been dispersed among multiple threads and the information is not very searchable. I myself am guilty of that because I started this thread to describe a roof-related project in two parts - fixing the Interstate's lap-welded roof seams that were beginning to rust, but then I began running Part 2 of the project (adding a thermal insulation coating to the roof) into the same thread when it's really a different topic. So I'll move that over here.

Most of the rest of the country is happy-clappy right now because they feel summer approaching. Here in Houston, we are in mourning. The spring equinox always brings a certain feeling of despair, because we know that crushing heat is right around the corner. And so it was that we met a personal milestone yesterday - the first day in 2017 when the temperature inside our Interstate climbed above 90 degrees despite some of our shielding measures being in place.

I'm upping my game on heat countermeasures for the Interstate, and now going forward in semi-quantitative rather than anecdotal terms, to better judge which measures are more effective than others, and thus worth undertaking. Yesterday I bought this low-end infrared thermometer at Lowes. We tested it out on some objects of known temperature (including the back of LB_3's throat) and it appeared to read reasonably accurately.

For your "read it and weep" moment of the day, here's what the wet bath exterior window of our Interstate was reading this morning at 9:40 a.m., with air temp 77 degrees, partly cloudy and breezy conditions, wind from the south:



Yup. 131 degrees. And it was only 9:40 a.m.! In the month of March! From this, you can get a feel for what we're up against at our latitude.

Obviously there is no hope of extending the Interstate's interior comfort range with that kind of incident energy impinging upon the entire side of the vehicle, because a great deal of it is going to be transmitted to the interior. Some of you might remember from last summer when I posted about having created this side shroud, which utilizes a reflective outer fabric layer:



After I put the side shroud on the vehicle this morning, I had to give it some time to cool down before I re-measured the exterior temperature. Here are the "before and after" readings for comparison.



You can see what I mean by semi-quantitative. It's not "science project" rigorous in terms of holding variables constant, but enough are held roughly constant to give a feel for the efficacy of the measure in question. I would look at those data above and conclude, OH HELL YES, I'm going to procure and use a side shroud analogous to this.

Speaking of which, someone on another forum had the same idea I had, but fashioned their side shroud out of Tyvek (like house wrap) instead of fabric. Brilliant! Most of the Tyvek that is described as "reflective" seems to be plain white. If I could find a mirrored Tyvek-like product analogous to how they do reflective plywoods in southern attics (radiant barrier), I'd be all over it.

My next big question is, will re-doing the roof in Bus Kote provide gains along the lines of what some Sprinter owners have claimed? The way to approach the answer is to measure the temps of the exterior roof and interior ceiling before and after application, under analogous conditions, so that task is in my immediate future.

In the mean time, if anyone else has any additional heat-bustin' suggestions or solutions, please recap in this thread.

Happy sweating.
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Old 03-26-2017, 02:41 PM   #2
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Entry edited above b/c I had accidentally reversed my sun angles on the first posting.
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Old 03-26-2017, 03:08 PM   #3
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Anything that is a lighter color than what you have now will be marginally cooler, the darker the color the more it absorbs the energy. No matter what, if you just paint it the heat will still build up and pass thru.

The way the reflectix works is that the bubble layer creates an air gap, so to not allow the energy to pass directly through.

What you need to think to do is to create an umbrella for the AI, your own personal shade tree, keeping it out of direct sunlight, with the ability for air to move around it.

Outside of that, I guess you could lay reflectix down on the roof to achieve some reduction.

130° in 77° air is horrible, although the ice storm I'm supposed to get tonight is getting pretty old.
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Old 03-26-2017, 03:40 PM   #4
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I applied a coating called Supertherm to my trailer and it made a huge difference. Sorry I didn't take any measurements. This is a ceramic bead coating. Compared to a piece of white aluminum siding which is hot to the touch a piece of aluminum coated with the Supertherm felt cool to the touch.
With the windows open the inside air temp was no higher than the outside air temp.
Al
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Old 03-26-2017, 03:43 PM   #5
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Wish I had taken some measurements before mods......Lew just covered most of my roof with solar panels.....wonder what the impact may have been. Too late to know now.....
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Old 03-26-2017, 07:48 PM   #6
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I applied a coating called Supertherm to my trailer and it made a huge difference. Sorry I didn't take any measurements. This is a ceramic bead coating. Compared to a piece of white aluminum siding which is hot to the touch a piece of aluminum coated with the Supertherm felt cool to the touch.
With the windows open the inside air temp was no higher than the outside air temp.
Al
We have a ceramic coating called Bus Kote arriving on Monday. InterBlog did the research on that so I can't speak to the specifics.
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Old 03-27-2017, 05:20 AM   #7
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Originally Posted by BigAl View Post
I applied a coating called Supertherm to my trailer and it made a huge difference. Sorry I didn't take any measurements. This is a ceramic bead coating. Compared to a piece of white aluminum siding which is hot to the touch a piece of aluminum coated with the Supertherm felt cool to the touch.
With the windows open the inside air temp was no higher than the outside air temp.
Al
This is very much along the lines of what people have said about Bus Kote in places like Sprinter Forum. They claim it makes a big difference. I was inspired to get the infrared thermometer because I'd love to know what "big" really means.

It's not helping our present situation that greater Houston had its warmest winter in recorded history. So did Texas as a whole, and so did Louisiana. There is speculation that we might see more early summer storm activity because the Gulf of Mexico is starting off the season super-charged with heat. Who knows - we might end up using our Interstate for our first hurricane evacuation this year. In which case, I sure want a thermal coating to be on the roof.
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Old 03-27-2017, 05:36 AM   #8
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...
Outside of that, I guess you could lay reflectix down on the roof to achieve some reduction...
I should have mentioned that part of this challenge involves space and weight considerations. I created the side shroud, which is held in place with neodymium dot magnets, because it's about 15 feet long but it folds down to the size of a large ham sandwich - easy to store in the small space of an Interstate. Its two layers of fabric are of an extremely light gauge. Tyvek would also fold to a small size.

I love Reflectix and use it for interior stealth window coverings and also for a measure of insulation from the inside out, but even storing items on the scale of window sizes became a creative challenge (blog post here). The issue with Reflectix is its bulk. It neither folds nor compresses.

Some Sprinter users have increased their insulation by adding bed liner compounds to their roofs. The problem with those is the weight - they can add a couple of hundred pounds, which in our case is totally out of the question because of the Interstate's GVWR and also there are center of gravity (CG) issues.

The Bus Kote and its bonding layer applications have a shipping weight of 34 pounds, but a lot of that is the water/alcohol/other miscible liquid base. Once applied and dried, the products will weigh substantially less than 34 pounds.
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Old 03-27-2017, 07:21 AM   #9
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Wish I had taken some measurements before mods......Lew just covered most of my roof with solar panels.....wonder what the impact may have been. Too late to know now.....
The more you roof is covered with the solar panels, the more it is like being parked under a shade tree, now the issue is side heating, if you have and deploy both awnings you'll have done pretty much all you can to cut down the direct exposure.

Interblog - sorry didn't realize the space side of the challenge, it does work well but it is a space hog. It does seem that for this sort of application, those types of paint should work.
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Old 03-27-2017, 07:35 AM   #10
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The coatings company looked at the emailed pic of my roof and said, "You need to make sure you reach under those panels and apply the coating right up to the side of the coach a/c [which is below the panels]." The reason is the variability of sun angle. Because our solar panels are vaulted, they only provide partial shading in most scenarios.

Now, if an owner has installed panels flush with their roof, that's potentially a different story.
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Old 03-27-2017, 11:09 AM   #11
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There are so many variables on this question. It's noon here now and with the parking orientation of our Interstate, the shadows it casts confirm that the sun is overhead, with neither side receiving more direct radiation than the other. It's been mostly cloudy all morning, so it's hard to get any worst-case data on shell heating. But the biggest current variable is not the sun but rather the wind, sustained out of the west at 3 mph with gusts to 10 mph. The leeward side of the Interstate reads 110 F, by virtue of the clouds (82 F air temp - shell temp would be higher on a blue-bowl day). But the windward side reads just 92 F. Most of that 18 degree difference is probably due to the air-cooled effect, although some could be residual load from earlier in the day when the sun angle was different.
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Old 03-27-2017, 05:39 PM   #12
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As a fellow Texan and Interstate owner, I will be following this thread with great interest. Last summer driving to northern New Mexico with both A/Cs going full blast the interior temp stayed stubbornly above 90.
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Old 03-27-2017, 06:44 PM   #13
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Move to a cooler climate?��
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Old 03-27-2017, 07:00 PM   #14
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Move to a cooler climate?��
Never! This is God's country. If it weren't so hot, humid, flat, and ugly, everyone would want to live here. Seriously, October through early May can be pretty nice. Many places don't have 7 or 8 months to camp comfortably. The low taxes, low cost of living, and dynamic economy are s nice perk as well.
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