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Old 08-01-2021, 07:02 PM   #1
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The Insanity and Vanity of Black Rooftop A/C covers...

A few years ago, some fool in RV sales management came up with the idea that putting jet black plastic covers on RV rooftop air conditioners would look really cool. It would boost sales. And, it did. It appealed to our basic vanity, that something must not just be functional, but sporty and stylish, too.

That guy ought to be flogged for the environmental damage from the extra wasted energy he personally caused. Moreover, he must have been asleep all through high school science class. He certainly never took applied physics.

If he had, he'd have known about the "black body theory". A black body is an idealized physical body that absorbs ALL incident electromagnetic radiation, regardless of frequency or angle of incidence. The name "black body" is given because it absorbs all colors of light. Especially heat.

In contrast, a white body is one with a "rough surface that reflects all incident rays completely and uniformly in all directions." [ Source Wikipedia]

In English, that black plastic surround on your Dometic or Coleman rooftop AC or heat pump is a "black body" and is actually absorbing heat, drawing it in.

Under that black plastic shroud, at one end, theres a condensing coil that has a fan blowing across it, whose sole job is to cool down hot refrigerant gases. Beneath the cover, below the roof line, separated only by thin sheet metal box, is the evaporator or cooling coil, which draws warm air out of the space using cooled refrigerant. A cycle that repeats over and over. Basic thermal transfer.

Wanna make this process harder and horribly inefficient? Change the plastic shrouds from bright polar white to jet flat black. Nothing sucks in more heat than that color (or lack of a color as Sheldon might argue.) It is a terrible concept. How it got past the engineering department baffles me.

But, black shrouds caught on faster than a new Nike design, and no one complained. Except me. I took HVAC engineering and physics. And, I hate black as a color, even if it's not.

Still, I'm surprised that younger climate change activists (and even ex-engineers) arent holding rallies all over Indiana. It's incredible to me that no one's noticed this, tested the temperature differentials betwen the two colors of shrouds, calculated the exact amount of wasted KILOWATTS ( yes, kilowatts) in a day, month, or year. (A great science project for anyone with middle schoolers on board!)

As for me, we bought a '19 Coachman Class A, and I despise its black AC shroud. And, the black fan shrouds, for that matter, which sport the same problem.

I went to buy a new white one, but the price is now north of $180. Ouch!

My solution will be far cheaper. I plan to remove that Grim Reaper shroud off my rooftop. Clean it thoroughly, rinse it, then paint it with a gloss ultra white Krylon paint. Then reinstall. There will be instant energy efficiency created.

Ive even found a good paint, perfect for the task: Krylon's FUSION series paint. It sticks to plastic, has lasting fade resistance and superior adhesion.

While I haven't yet calculated the ROI from this simple energy efficiency mod, I know it will be significant. Just ask any dog who avoids walking on black asphalt in the summertime. Maybe I can start (restart) a new (old) trend.


https://www.lowes.com/pd/Krylon-FUSI...-oz/1000460279
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Old 08-01-2021, 07:19 PM   #2
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Agreed and it's really crazy that they charge more for high capacity models when likely a similar efficiency could be achieved by white shrouds.
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Old 08-01-2021, 07:39 PM   #3
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Never gave this any thought. But then we park under trees and in the shade.

Does that count?
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Old 08-01-2021, 09:22 PM   #4
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My roof AC cover is white. I'm now thankful for that!
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Old 08-01-2021, 10:52 PM   #5
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I replaced my roof top heat pumps on a prior coach. When I placed the order at my service place, they gave me a 'quirky' look when I ordered white covers. and asked if I "really wanted white".

Long enough ago that I don't recall if there was any price difference.

It seemed like the right thing to do then.

Current coach has lots of black paint, including the heat pump covers.

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Old 08-01-2021, 10:54 PM   #6
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I am not disputing that black takes on more heat.

I would be entered in actual data that show how different the two colors are.
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Old 08-01-2021, 11:19 PM   #7
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I have felt the same way since I first saw those black covers. I am not an engineer but I spent 20 years as a millwright repairing, maintaining and installing billions of dollars of steel production equipment. Anything that needed to be kept cooler, a relative term in steel processing, was always painted white or silver for good reasons. Having owned 2 black vehicles in Phoenix, AZ I can attest to the heat gain when compared to my current white truck. I will be interested to see if any comments disagree with the OP's premise.
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Old 08-01-2021, 11:20 PM   #8
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If you really want to make your brain hurt.... Think about how the air conditioner under that cover HAS NOT CHANGED AT ALL in about 40 years or more. Still the exact same tech and poor efficiency overall.
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Old 08-01-2021, 11:54 PM   #9
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The same issue applies to all of the black paint on coaches. Living in the southwest, black is the last color you want your coach painted!
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Old 08-02-2021, 12:42 AM   #10
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It used to be that anyone with an IQ above the moron level understood that but then we have to take into account the dumbing down of society....

I ride a motorcycle. My leather jacket is white. This is in direct opposition to every other leather jacket worn on every Harley ever made on the entire planet. If you really want to experience heat, try riding a motorcycle with an engine between your legs while wearing black leather gear in the heat of the summer.....

You know what else is really interesting? All you ever hear about when you get a motorcycle is how dangerous they are because no-one can see you. So the first thing every single motorcyclist in the world does is buy a black bike and buy a black leather jacket....

But..I digress. I love the idea you have with respect to your AC covers. We just got a 2020 Coachmen and as soon as I saw the AC covers I said to myself, how stupid is it to have a heat rejection device and paint it flat black?

Henry Ford used to sell Model T's in any color you wanted as long as it was black. It seems...for some reason..that if it was black the car dried faster and they could make more of them faster. I wonder why that is?
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Old 08-02-2021, 06:07 AM   #11
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I can tell you for a fact that black vent covers and other plastic parts last longer in sunlight than white ones. White ones get brittle and crack much sooner.
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Old 08-02-2021, 06:32 AM   #12
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I think the theory is good, but you would need to provide some side by side data to convince me - since so much of the heat is coming from the system itself vs solar gain from the black cover.

The systems have changed some over the years. We are on our 3rd or 4th generation of gas. We commonly have heat pumps instead of just ACs. The newer ones have 2 motors so use better matches demand. The basement ACs were probably the best, since they were standard small home units, but I don't think anyone is doing those anymore.

The DC compressors and variable speed motor will eventually make it to the RV AC market. Probably as soon as all the RV parks start charging really high usage rates, so the RV owners start demanding the upgrades. However, with only 2 manufacturers it may be a real challenge to get them to spend the money.

Sounds like a great opportunity for a market disruption with a new player, or an existing home AC manufacturer to enter the market.
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Old 08-02-2021, 06:55 AM   #13
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Quote:
Originally Posted by Teamfoxy View Post
I can tell you for a fact that black vent covers and other plastic parts last longer in sunlight than white ones. White ones get brittle and crack much sooner.


Interesting! I also remember that early rubber tires looked very whiteish color, but the addition of carbon black made them last much longer.
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Old 08-02-2021, 06:56 AM   #14
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I've made a living cleaning boats for 30 year. Just last week we cleaned a brand new $100,000+ open bow with black carpeting. Try walking on that with bare feet when the sun is out.

And don't get me started on curved windshields that are virtually impossible to clean from the inside.

Design engineers should be required to maintain or attempt to maintain their creations.
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