The outside of my coach is painted a dark blue. The skins are a magnet for heat. Being that they are riveted to the structural spars of the coach, that same heat is being transmitted conductively to the spars. The spars, now at 150+ degrees are conducting that same heat to the aluminum ceiling panels where it is being distributed throughout the coach, bringing the inside temperature past 115 degrees.
No wonder people install 3 rooftop air conditioners.
I see some sort of thin tape that MCI applied, I guess, to help curb the process, but that tape is hard and crusty and no longer works.
If the space shuttle can travel through heat over 1000 degrees, I should be able to make my coach into a thermos bottle.
Anybody have any ideas?
I want to be cool again man! 8)
Thanks!
After stripping the interior of my bus, I screwed 1x2 fir strips horizontally to the wall uprights. Then had 2.25" of spray foam installed. But since you can't do that, repainting white will make a big difference. Good Luck, TomC
That separation tape is not for heat it is for dissimilar metals so they don't touch each other and cause corrosion. Like steel against aluminum etc.
Never thought about the electrolysis issue. Hmmmmmm.
I guess MCI didn't give it much thought; having a 5 ton compressor in the back, pretty much took care of the heat problem here in Phoenix.
I like the wood furring strip idea... thanks!
http://www.deansteelbuildings.com/products/panels/sr-sri-by-color/ (http://www.deansteelbuildings.com/products/panels/sr-sri-by-color/)
This chart should be the primary determinant of exterior color, at least if you live anywhere the sun ever shines!
I'll be painting my bus's sides Almond. It has almost as good solar reflectivity as white, and it's a stock Rustoleum color so no worries about getting touch-up in the future. Unfortunately the dark blues are not too good for SRI, as you've found out. When I repainted the roof I used the ceramic insulation pixie-dust in the white paint - I think it made it slightly cooler / less hot, and every little bit helps. My eight big solar panels up there do however make a BIG difference to interior temperature.
In an ideal world you'd insulate everything, but sometimes it's just not possible or feasible.
John
The Dean Chart is interesting in that the Almond color has a higher SRI than Polar White and Oyster White, which does not seem logical. I have to wonder if a mistake was made in compiling the chart.
A while ago I painted swatches of different colors onto a sheet of aluminum to see which would be hottest in the sun. With a cheapo IR thermometer (not very accurate at best) and my hand, it seemed that pure gloss white and almond had the same temperature, School Bus Yellow and light grey were slightly hotter, gloss black was hotter still, and surprisingly the bare unpainted aluminum was the hottest. Was this a scientific test - heck no, but it confirmed why light colors make sense in hot climates.
And that's why I'll be painting my bus Almond! Is it the nicest color - no, not really, but it should help keep interior temperatures reasonable. White shows the dirt too much, otherwise I would use it for the bodysides. The roof color is more important than the sides - that's where most sunlight hits, so it has to be white.
John
I once bought a powder made out of tiny foam beads that supposedly decreased that thermal transfer when added to paint. I ended up adding it to the roof coating the last time I did it. I really do not know if it made any difference. Anyway, I believe there are thermal paints that might help.
Looked like silver was the best at the top. Mine is silver with white top.
Funny thing about metal and paint my bus is setting in the shade both the black and white paint are identical in temperatures the ambient temperature is 104F so is the metal
I have shot temps of as high as 184 degrees on the side of my bus on a flat black panel blocking out one of my windows.....the gloss black piece right next to it was a bit cooler.
According to that chart, which has three different whites, snow white is the most reflective. I am not sure I could tell the difference between snow white and polar white though unless there is a dwarf around to help. Dark green seems to be the least, and black is not included. I once read that dark green absorbed more heat than black but do not really know if that is true.
I did mine like Tom C but used 3 @ 3/4 " strips at the top centre and 2 @ the start of the roof at the walls of ply for both added spray foam and to stop the heat transfer + a lighter colour would help
dave
Not sure where they got their chart numbers. There was a link on here at one time to the NACA study. Most reflective is a shade of blue. The almond is a pale shade, actually used by Ford as Wimbledon White..rdw
The new State trooper patrol cars in Az are now painted shades of blue and they say because of the heat here the blue is supposed to be better than the old white for heat fwiw it is a pretty shade of blue
I suspect the glossyness of the paint is a major factor as well. I just don't get it why some folk want matte black cars here - they must be like an oven inside. I'm curious what difference there is between oxidized unpolished aluminum, highly-polished aluminum or SS, and silver-colored paint for heat reflectivity.
The Tuareg tribesmen of the Sahara traditionally wear blue robes - I read that they are cooler in the sun than other colors. So maybe this whole color/reflectivity/coolness thing is more complicated than I thought!
John
I deal with that by not living in or near the deserts. Sam Kinison had something to say about deserts. Isn't there an RV roof paint that has ground up pearls or something in it to help insulate?
Well, it looks like lighter colors reflect the sun better, but not everyone wants a white bus. I wish there was some scientific testing of the various colors in glossy automotive enamel (urethane) that would positively identify a ranking of the usual colors. The Dean chart might have only been for roofing colors. The opinion that some blues do better is interesting, I just wish Candy Apple Red did better. I want it all, cool temps, flashy color, and low cost, so I think I'll paint the roof white, and the rest in red with a white undercoat.
In July 2013 I measured the temps on the side of my bus and I believe it was around 170F. The swatch I tested was a dark green color.
Zip Dee window awnings helped significantly on our 4104.
I have solar screens on all my windows, in addition to the awnings. The solar screens do make a huge difference in dropping inside temps, but the window awnings are the most effective by far. Get the sun off of the windows all together is the best way.
We have the roll down MCD off white vinyl with Black Solar mesh on the other roller. It does cut down on heat a bunch.
I spent about an hour putting together a post and attached a couple of pics. Got a message that the pics were too large and it erased the entire post.
all that work lost!
Boo
C'mon... this is the 21st Century Forum Master/Web Master. Lets get with it! >:(
Well... I have found the Holy Grail of heat tapes. It is called CeraTex® Ceramic Fiber Tape. I am applying this to all of my spars and metal cross-overs; it has an adhesive backing which is really handy! Afterwards, I am securing furring strips on top of the tape screwed to the spars and filling in the additional 3/4 of an inch with insulation between the wooden furring strips.
The spar... EXTREMELY HOT!
The Ceramic Tape... Warm.
The wooden furring strip... just noticeable.
The difference is dramatic.
The walls had 1 3/4 of insulation. Now with the addition of the 3/4 wooden furring strips and additional insulation within the furring strips and the paneling, the walls are just a little over 3" thick.
CeraTex® Ceramic Fiber Tape (with adhesive backing) - 1/8 x 4" x 100' roll - $100
Great Stuff!
Mineral Seal Corporation
1832 S Research Loop, Tucson, AZ 85710
(520) 885-8228
http://minseal.com/ (http://minseal.com/)
Talk to Sheryl
Email me for pics.
Thanks all for your input!
Mike
Very interesting. Their ceramic fiber blanket material might be useful for lining engine or generator compartments to reduce heat and act as a flame retardant. There are several products that do that, but the problem is usually minimum order cost. It looks like they might be more flexible in selling smaller orders.
We are painting our bus very near to black. Wish us luck
Sent from my iPhone using Tapatalk
Quote from: Scott Bennett on August 07, 2016, 07:27:15 PM
We are painting our bus very near to black. Wish us luck
Sent from my iPhone using Tapatalk
Even the roof? Well, at least you are well insulated.
Scott is this your's? ;D
Looks like the roof is white, even though everything else is black. 8)
This was the thermal camera video I shot in my bus last year when I was working on improving my insulation. It's spray foamed met the spars still show up and the metal screws are extremely visible. There is reflectex and plywood over them and then covered with fabric. I love my flir camera.
https://youtu.be/XXZYoU4aIbE
I thought everything was going hunky dory and then I put an aluminum ceiling panel back up; and it gets very warm. The heat is not coming through the ceiling, it is coming through the yet to be taped spars... migrating through the bus and heating up the aluminum panel. The aluminum panel is screwed to wooden furring strips and there is 2 3/4 of insulation above the panel. I think I'm going too lose the aluminum panel and replace it with 1/8" Masonite which will be covered with thin carpeting anyway. This heat thing seems to act like capillary action. The heat goes where it is not.
This Thermal Management thing is a real bug a boo with these metal buses. Any Thermal Management Engineers out there?
Scott... what would you charge to FLIR me?
Thanks!
Mike
N9EWS
"Those who say something can't be done - should stop bothering those who are doing it!
White roof, aluminum sides, one dark brown band , one air conditioner, no problem...
I bought that flir for $129 I think?? It might have been $99 I don't remember exactly, it was on sale. It clips on my iPhone. Amazing technology at a cheap price. Flir one is the model I have. It's for an iPhone 5 But I modified it to fit a iPhone 6 the one for the iPhone six cost $299 at the time. The iPhone 6 model did have double the resolution but I am fine with the cheap one I got. They make them for several smart phone brands. I've got some cool video other my 71 series running. On my 671 inline the hottest thing on the visible side of my engine is the coolant line coming off the oil cooler. I can see plugged tubes in a radiator too with it.
Stop by any Empire Cat dealer in the Phoenix area they will FLIR for you all their techs have the S60 Cat phone with the FLIR feature.I have the S60 Cat phone that I have been playing with the last 2 weeks it's a neat gadget and Cat guaranteed me I cannot destroy or drown it lol we will see