The Insanity and Vanity of Black Rooftop A/C covers...

[wolfe10]

Originally Posted by Dutch Star Don

Just a suggestion.....once you remove the OEM cover and screws, the screws tend to break the cover and the cover will eventually fly off. Whenever I removed an A/C cover, I added rubber backed washers to the screws to increase the surface area of the screw. Many also add a couple of additional screws with rubber washers to ensure that the cover stays on as it gets brittle over time.

Yup, been using SS fender washers with piece of innertube under them for decades to spread the load and reduce cracking of the A/C covers.

[Alpine36]

Originally Posted by BobJones

There's an easier way and it's more fun. Go to the big Island (Hawaii) and walk on a black sand beach barefoot. Then go to a white sand beach and walk barefoot. Your feet will explain it to you

I like that idea. Then we'll sit under two shade canopies in the full sun with a slight breeze for a cold one. Yours is white, mine is black. I'd bet you another cold one you couldn't tell the difference. But yeah, those black sand beaches are brutal on the feet.

[RM Art]

Originally Posted by Mudstream

Another question. What changed in the environment? Temperature? Cloud cover? Humidity? There are still too many unanswered questions.

Studied answer:

Annual increase of overall global heat range is the reason for climate, environment, humidity and other natural-items' occurring alteration levels.

Civilization's created initiator of [and predominant continuation reason for] this planetary heat increase is the amount of carbon dioxide released into atmosphere over the past 100 + years. CO2 in atmosphere is approaching 2X PPM over and above what Earth's natural conditions had run on for some 12,000 years of continual relatively comfortable seasonal climate conditions.

Airborne CO2 is a solar heat collector. Due to its initiation and during its continuation of global warming other global warming assistance items come into play. They are termed "feed-ons"... in that, they feed on the global warmth to consistently create even more warmth increasing dimensions.

Feed-Ons include but are not limited to:

1. Glacier reductions that substitute their solar heat reflective white surface for exposed dark land masses that absorb solar heat.

2. Sea Ice reductions that substitute their solar heat reflective white surface for exposed dark water masses that absorb solar heat.

3. Increased global humidity that absorbs solar heat.

4. Permafrost melting that releases many thousands of years trapped [i.e. sequestered] CO2 and other solar heat absorbing gases.

Of course there are other human doings that also contribute to global warming via increased CO2 in atmosphere. Burning Amazon forests and huge increase on meat product animal farms are two additional causes.

End Result: All humanity is entering into Global WAR [i.e. We Are Resilient]. Wherein, before too many ecosystem calamities occur we must remove enough CO2 out of atmosphere to stop this increase in global warming. Can we do it - YES. Will we be successful in doing it - that is yet to be seen.

[FL420]

Originally Posted by bluemoontwd

The best of both worlds. Try just painting the top that gets the most sun white leaving the sides black. They still look good and reflect the heat.

And that's why school bus colors are yellow on all sides for good visibility in poor meteorological conditions and white on top for cooler cabin interiors in hot sunny conditions.
https://www.accuweather.com/en/weath...l-buses/989698
These days many if not most small activity buses are painted white all over.
[emoji40][emoji382]

[TandW]

Originally Posted by RM Art

Studied answer:

Annual increase of overall global heat range is the reason for climate, environment, humidity and other natural-items' occurring alteration levels.

Civilization's created initiator of [and predominant continuation reason for] this planetary heat increase is the amount of carbon dioxide released into atmosphere over the past 100 + years. CO2 in atmosphere is approaching 2X PPM over and above what Earth's natural conditions had run on for some 12,000 years of continual relatively comfortable seasonal climate conditions.

Airborne CO2 is a solar heat collector. Due to its initiation and during its continuation of global warming other global warming assistance items come into play. They are termed "feed-ons"... in that, they feed on the global warmth to consistently create even more warmth increasing dimensions.

Feed-Ons include but are not limited to:

1. Glacier reductions that substitute their solar heat reflective white surface for exposed dark land masses that absorb solar heat.

2. Sea Ice reductions that substitute their solar heat reflective white surface for exposed dark water masses that absorb solar heat.

3. Increased global humidity that absorbs solar heat.

4. Permafrost melting that releases many thousands of years trapped [i.e. sequestered] CO2 and other solar heat absorbing gases.

Of course there are other human doings that also contribute to global warming via increased CO2 in atmosphere. Burning Amazon forests and huge increase on meat product animal farms are two additional causes.

End Result: All humanity is entering into Global WAR [i.e. We Are Resilient]. Wherein, before too many ecosystem calamities occur we must remove enough CO2 out of atmosphere to stop this increase in global warming. Can we do it - YES. Will we be successful in doing it - that is yet to be seen.

What?!

[Adaycj]

Originally Posted by Mudstream

OP: You should have just painted the covers white and not touched anything else and posted the results from that. The original dissertation did not mention insulating and taping the evaporator housing. What else did you change?

Sorry but I'm still not buying it.

I'd be excited to see more results from a source with a little more tilt towards science and less towards drama. It's hard to get a real apples to apples comparison without setting up a full blown experiment. Simply choosing performance metrics that aren't largely based on the weather days apart and measurement bias would help.

I'm not buying it either, but I do find it interesting that so many think the science here is so obvious here that no testing should be done. I know better, but I'm just me.

[hikerjohn66]

Originally Posted by WalkTheWalk

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

Very interesting argument and you could be correct although, it would be helpful to see a heat transfer study on it to confirm that it's a significant factor. If there is a lot of air moving around under the cover, radiation from the inside (mostly top) surface onto the working components may not be a big factor. But since it would take and expert study, I doubt it will happen.

Perhaps you will be able to get a good feel for how much your paint change will make if you can compare how much less time the ACs have to run per unit of time to maintain the same inside temperature during the the same period of of day and with the identical weather conditions.

You'd probably also want to have the ACs in the full sun exposure instead of under the shade of a tree where the sun does not directly strike the covers.

It would be nice if you were to report to us how your results come out.

[CRV2]

Regarding studies, while I have never seen a study for the color of an RV A/C shroud, I have seen related studies regarding home central air conditioners and whether having the outside condenser in the shade vs in the full sunlight would make the A/C more (or less) efficient and the results were...... no difference. Which gets back to my earlier comment in this thread that the A/C's efficiency is related to the ambient air temp and not the color of the shroud, as with a large airflow (like the A/C condenser has) any air in the a/c unit while not running (hotter air if the shroud is black vs white) is quickly exhausted within seconds.

Not that I suggest anyone read this, I skimmed over it:

FSEC-PF-302-96

From the end of the study paper in the discussion section:
"our measurements did not allow us to conclusively determine that AC condenser shading, when limited to the immediate area surrounding the condenser unit, provides statistically consistent reductions to cooling energy use."

and in that same section: "The probable explanation for the lower than expected performance in the experiments is that outdoor AC units draw in a volume of air that greatly exceeds that of the nearby shaded air volume." ~CA

[TandW]

I'd like to hear an "Engineer's" dissertation on Mother Nature's want to endow a few of us with quite a bit of extra melanin.
PS. I have a rooftop heat-pump shrouded in black. So cool!!!