Roof paint for a car? (Repel heat / keep interior cooler)

[hayden55]

Originally Posted by California98Civic

I have very high quality (and expensive) ceramic and metallic heat rejecting tint on my car. I can feel very significant and Marge difference if I roll the window down versus rolling it up from the Sun on my skin. That's not science of course, but it confirms some of what testers have shown.

a while ago on the Prius I found the numbers for the oem windshield heat rejection tint and added the numbers of my 3m Crystalline to it.
Windshield: OEM + 70% 3m Crystalline = 56% VLT, 79% TSER.
Drivers Window: OEM + 40% 3m Crystalline = 25% VLT, 78% TSER.
Big difference in HVAC needed, you can feel the difference on a sunny day if you roll down the rear window in the sun and pass your hand back and forth. I can usually roll around town with very minimal HVAC use most of the time none up to about 30 minutes.
Running around town on short 10-15 minute trips with the AC set on 71 Auto with the vents screaming vs not using the hvac is the difference between 39 mpg and 55+ mpg for those short trips.

[hayden55]

https://ecomodder.com/forum/showthre...d-34665-6.html

post #57

[Jez77]

Originally Posted by hayden55

I've always read the exact opposite.

"The researchers developed a thermal model that predicted the air conditioning capacity (rate of heat removal) required to cool each vehicle to a comfortable final temperature of 25°C (77°F) within 30 minutes. (This is an industry standard for vehicle air conditioner performance.) Based on the experimental measurements, the analysis predicted that the capacity required to cool the cabin air in the silver car is 13% less than that required in the black car."

"Using a white or silver paint (solar reflectance = 0.60) instead of a black paint would raise fuel economy by 0.44 mpg (2.0 percent). It would also decrease carbon dioxide emissions by 1.9%, and reduce other automotive emissions by about 1%."

https://eta.lbl.gov/news/article/110...duce-emissions

I know the Prius has a 4500w HVAC so that would equate to about 292.5 watts saved for that 30 minutes then level off. That's pretty significant given its smaller hybrid battery and how much using the hvac kills the battery around town when the engine is off at stop signs or coasting.

I remember reading a more detailed report in 2016 on window tints, and vehicle colors but I couldn't find that one.

I second the IR gun in a parking lot. You could easily measure roof surface temp and cabin temp with them. I'm gonna do that one day when I'm roaming around campus with my IR gun.

I'd say when you get some measurements buy a can of white plastidip and have at it.

That's probably correct.
The article I read the cars where parked with windows up for the test. Although all cars reached the same temp the dark cars got there quicker so logically the ac would need to work harder in dark cars to combat the temp rise.

[Jez77]

Originally Posted by Shaneajanderson

I guess I have a hard time believing that. I have a white pickup and we just sold our black van. I could get in the pickup in the summer sun, roll the windows down and it was fine immediately. The van however was always dramatically hotter inside, though I never took temperature readings, it's very obvious from just what I've seen with my own cars it makes a difference.

In the article I read they were testing identical cars.
My black work van is particularly bad as there is no headlining in the back part of the van so you get a lot of radiant heat straight off the steel into the cabin. It's not a nice place to be on a 40deg Ozzy summer.
Yet I use to own a black fastback that was much cooler.

[aardvarcus]

I painted my Suburban's roof white. The factory paint was completely baked off and it was starting to surface rust. I wanted to keep it from getting worse, so I did quick surface prep, primed, and painted. It has helped it some, but it would have been just as effective to put some insulation between the headliner and the roof. In fact, when I finally get around to repainting the entire vehicle I may do just that and return the roof to the body color.

[oldtamiyaphile]

https://ecomodder.com/forum/showthre...oof-35655.html

Most colours I've found sit in the 50*C range in the sun. Black sits in the 70+ range. My (not very shiney) grey trailer was the hottest colour I ever tested at 90+ and hotter than my black Jeep parked along side.

White is the coolest other than chrome- a chrome roof will stay wet all day after a morning shower and is at least 5*C cooler than white.

Only buy quality, genuine branded wrap. eBay wrap will crack and peel after a couple of years.

Tint's been tested too:

https://ecomodder.com/forum/showthre...ted-35441.html

8*C cooler on interior surfaces.

[Shaneajanderson]

Originally Posted by oldtamiyaphile

https://ecomodder.com/forum/showthre...oof-35655.html

Most colours I've found sit in the 50*C range in the sun. Black sits in the 70+ range. My (not very shiney) grey trailer was the hottest colour I ever tested at 90+ and hotter than my black Jeep parked along side.

White is the coolest other than chrome- a chrome roof will stay wet all day after a morning shower and is at least 5*C cooler than white.

Only buy quality, genuine branded wrap. eBay wrap will crack and peel after a couple of years.

Tint's been tested too:

https://ecomodder.com/forum/showthre...ted-35441.html

8*C cooler on interior surfaces.

Those differences are quite substantial

[Jez77]

A good article done by RACQ in OZ on temps in cars.
Shows only a 3 deg difference between black and white and not much difference in rate of temp rise either which surprised me.

https://www.racq.com.au/~/media/pdf/...rvey_2009.ashx

[freebeard]

Originally Posted by hayden55

I'd say when you get some measurements buy a can of white plastidip and have at it.

Seconded.
pro: removable (if you put it on thick enough)
con: cost 1.5x regular paint.

Trees are Forest Green for a reason. On a red car I'd go with https://en.wikipedia.org/wiki/Mountbatten_pink, the manliest pink. That's (#997A8D) in hexidecimal RGB.


http://1.bp.blogspot.com/-t7np81atTN...pg%2Blarge.jpg

[oldtamiyaphile]

Originally Posted by Jez77

A good article done by RACQ in OZ on temps in cars.
Shows only a 3 deg difference between black and white and not much difference in rate of temp rise either which surprised me.

https://www.racq.com.au/~/media/pdf/...rvey_2009.ashx

That's because most of the heat comes in through the windows of a typical car.