Chrome wrap your roof!

[oldtamiyaphile]

Originally Posted by ShinyMew

I wonder how much of a difference it makes compared to white paint.

I have a white car with a black roof, I plan on testing the extremes later on, but I expect decent gains even from white, as chrome is still much more reflective.

Also, without an air gap below the newfound reflective barrier, won't conductive heat win in the end?

There's no conduction without heat (or a heat differential to be specific). By reflecting more heat, there's less heat energy for conduction too. If I park in the open and the sun is that low, then the sides will still be open for conduction.

You can find a few tests online of white vs dark cars parked in the sun, the white car always stays cooler, chrome is like white+. It stays so cool that the roof remains wet in the evening after a morning shower on a warm day.

Vinyl is also apparently a PITA to remove, especially from surfaces hammered by UV. I wonder if Plasti Dip with Silver Metalizer would work well or be easier to remove?

Plasti-Dip is expensive by comparison (in AU at $20+ per can), require masking off, and not as reflective.

The wrap is said to have a life of 3-5 years, but you can imagine that a matt black wrap (that tends to be all the rage) absorbs much more heat/ UV and therefore won't last anywhere near as long as chrome.

I removed the 'Jumbuck' lettering on my dark coloured ute after seven years, the lettering was all cracked and flakey. A bit of heat with the heat gun and it came off no problem at all. Barely even needed the wax/ grease remover (which frankly works amazing for removing sticker residue).

[ar5boosted]

Originally Posted by cRiPpLe_rOoStEr

Not sure if that's the same type of film, but I have already seen one that is used to turn the rear window into a mobile billboard from the outside, while still retaining most of the visibility from the inside. There were times when it seemed that nearly every taxi in my country had it...

That's the product. I think it's made by 3M

[cRiPpLe_rOoStEr]

Originally Posted by ar5boosted

That's the product. I think it's made by 3M

I don't remember its manufacturer, but it's been less common back here nowadays. Anyway, it didn't really seem to provide the same degree of heat blocking as regular tint does, even though both this product and regular tint can be used simultaneously, and it eventually being of a lighter color than the tint it might increase the reflection and effectively decrease the heat conduction to the inside of the vehicle.

[oldtamiyaphile]

I've been experimenting with 'shadow chrome' as a less obvious alternative to full chrome. On a car it looks like a medium metallic grey. Shadow chrome on the left:



A TJ hardtop is basically an A/C torture test. Matt black is the worst possible colour for reflectivity and emissivity, plus there's no headliner, so there's no insulation. On a hot drive, the underside of the roof gets way too hot to touch- well into the 70*C range.

Mounted on the Jeep- there's enough curve in this roof to already require post shrinking:



All but invisible from normal viewing angles:



Lessons learned:

Wrap doesn't stick too well to the textured surface. Post shrinking helps, but I've had to add electrical tape to the edges to prevent them peeling. That's OK as in an off roader I expect dirt will creep in over time, and the electrical tape makes an easily replaced first line of defense.

Shadow chrome has similar performance to my van's green paint, which is about +7*C vs white. That's not bad, but next time around I'll go with full chrome given how little you can see of it. The performance of full chrome is amazing.

[samwichse]

Or maybe if you're feeling fancy...

[mattrod]

Originally Posted by oldtamiyaphile

I've been experimenting with 'shadow chrome' as a less obvious alternative to full chrome. On a car it looks like a medium metallic grey. Shadow chrome on the left:



A TJ hardtop is basically an A/C torture test. Matt black is the worst possible colour for reflectivity and emissivity, plus there's no headliner, so there's no insulation. On a hot drive, the underside of the roof gets way too hot to touch- well into the 70*C range.

Mounted on the Jeep- there's enough curve in this roof to already require post shrinking:



All but invisible from normal viewing angles:



Lessons learned:

Wrap doesn't stick too well to the textured surface. Post shrinking helps, but I've had to add electrical tape to the edges to prevent them peeling. That's OK as in an off roader I expect dirt will creep in over time, and the electrical tape makes an easily replaced first line of defense.

Shadow chrome has similar performance to my van's green paint, which is about +7*C vs white. That's not bad, but next time around I'll go with full chrome given how little you can see of it. The performance of full chrome is amazing.

Great idea. I will try it on my JK's hardtop.

[Piwoslaw]

When I saw this I immediately thought that instead of reflecting all of that light, you could use it. Gascort deleted his alternator and supplemented by covering his wagon's roof with PV:
Solar roof

Originally Posted by oldtamiyaphile

Can't legally do it on the rear window though so I think the gains are fairly small, and only when the sun is at a low angle.

And this is where a Kammback comes in - as a shade for the rear window. If done right it also improves aero.

Regarding which coating reflects heats better, there is a thread about it, only for house roofs:
white metal roof vs traditional silver metal

Originally Posted by JockoT

I wish! Here in Scotland I get my best mileage in the summer

You mean all 2 days of it?

[oldtamiyaphile]

Originally Posted by Piwoslaw

When I saw this I immediately thought that instead of reflecting all of that light, you could use it. Gascort deleted his alternator and supplemented by covering his wagon's roof with PV:
Solar roof

If anything that's a cautionary tale. IRC Gascort actually went backwards and his consumption went up after installing panels/ alt delete.

Flexible panels only have a life span of ~5 years (my first one died at four years). Which means the payback is... never. Glass panels are bulky, heavy, fragile and will probably ruin your aero.

Solar panels turn 20% of the light that hits them to electricity, much of the rest is turned to heat. Not really an eco mod any more than painting your white car's roof black would be. The temp gain is a solid 30+*C, vs white.

In a cold climate the panels might not give you much of a boost, and in a hot climate, you'll always want to park in the shade. The energy from your solar panels won't be enough to offset the A/C use from being parked in the sun.

Anyway, the chrome wrap was step #1 in my http://ecomodder.com/forum/showthrea...els-35415.html

I have relatively specific needs, but my overall opinion agrees with the EM consensus that panels belong on your house, not your car. My gain from 340W panels/ alt disable is ~0.2l/100km or 3%.

[JSH]

Originally Posted by oldtamiyaphile

Comes in any colour you can imagine -solids, metallics, brushed, holographic, luminescent etc. White will be much less effective, but I understand chrome might not suit every situation.

If I'm remembering my Heat Transfer class correctly white is actually cooler than chrome. Something about the E-value. Then there is the childhood lesson of touching chrome seat belt buckles!

Our Campervan is brown and painting the roof is on the list of future mods.

[oldtamiyaphile]

Chrome is much more reflective than white, that's why you can see yourself it it.

The performance of white sits about half way between chrome and light colours (red, light blue, light green).

There's a reason why radiant heat insulation is always chrome (or gold), and why they use mirrors to reflect light onto molten salt reactors and not white panels.

The seat buckle feels hot because metal transfers heat faster than the plastic surround even though both are at the same temperature. Same principle hot coal walkers use - high temps- inefficient heat transfer.

My chrome roof now stays wet after a morning shower for the whole day, I've never seen that before.