Chrome wrap your roof!

[freebeard]

You can stand the shoeboxes on end for the test. What kind of thermometers? I still need to replace my infrared remote thermometer; one would work fine for this.

[seifrob]

Standard oven thermometer should do, just make sure the tip/needle is inside and scale/display is outside the box so you do not need to open it. I have two thermometers with thermistor on 1 m long cord and I plan to use them, when I have spare timine.

The reason behind white roofs is safety regulation, I guess. I asked local police about chrome roof and the answer was i would get pulled over for blinding other drivers.

To CrippleRooster: actually, as far as I know, better than Land Rover white roof was their tropical roof. Essentially white metal roof about one inch above normal roof. It reflects sun radiation and the one-inch air gap prevents heat to be conducted to the car. Images can be found on Google, one example from ipocars.com:




If you have spare white coroplast sheet, attach it to the roof rails and call it good enough.

[ratgreen]

This is great.

On the flip side, get a matt black wrap for winter, to get the heat in and stop wasting warm up times and engine heat into the cabin.

[gumby79]

It took 2 things to make the A/C up to task in Las Vegas summers on my grandparents '61 GMC short wide1/2t 1 White roof 2 small back window.

Chrome vinyl should be much better then chromed metal. The base material in the vinyl is insulative. Where is Chrome metal and mylar both lose out when they're in physical contact with the cold side.

Yeti used copper lining on the outside of the inner wall on there cups. BLOTER REDUX: YETI HOW IT WORKSAvE did it tear down on one and explain the copper lining insted of typical chrome.

[oldtamiyaphile]

Originally Posted by JSH

When you do your experiments just remember that infrared thermometers are not accurate on reflective surfaces. From Omega:

"In general, the higher the emissivity of an object, the easier it is to obtain an accurate temperature measurement using infrared. Objects with very low emissivities (below 0.2) can be difficult applications. Some polished, shiny metallic surfaces, such as aluminum, are so reflective in the infrared that accurate temperature measurements are not always possible."

Remember, we are not launching space craft or building medical equipment.

A polished metal pot with boiling water in it shows 99.9*C. I call that close enough.

The only time it's a problem is if you aim at a mirror and there's a heat source in the reflection. IR from the heat source is reflected into your lens, so the temp reading will only be hotter.

Here's a photo of two mirrors, left inside at the same temperature:



One has a matte vinyl backing to the camera. Extreme opposites of the emissivity range. There's at most a 1*C variation between the two. Any heat source reflecting off the mirror would be immediately obvious.

[oldtamiyaphile]

Originally Posted by JSH

As do school bus manufacturers

That's like saying manufactures prefer not to use full boat tails, as though a pure single function is the only goal.

The bus is white because chrome would add thousands to the cost of each bus for virtually no benefit.

Originally Posted by freebeard

NASA and SpaceX seem to prefer white.

Nope. I've never seen a satelite painted white. They often spend a lot of money on real gold for the lowest possible emissivity (0.05).



Rockets are white for cost, simplicity and/or simple practicality reasons. A cheap chrome wrap probably won't stand up to mach 30.

The whole emissivity argument is probably a non starter anyway since there's no real chrome in chrome wrap. The top layer at least is plastic which has the same emmisivity as car clear coat.

[oldtamiyaphile]

Originally Posted by seifrob

The only valid test should be performed so: take two identic cars, one with chrome roof, one with white. Put them on the parking lot, put a milkjug full of water in each car, immerse thermometers in milkjugs, measure temperatures every 10 minutes or so. Compare curves.
Ecomodder plausible test: take two identic shoeboxes or banana boxes, chrome top and white top. Take half litre bottle instead of a jug, use the same procedure.

When you park a black car in the sun, vs a white car, you only see a few *C difference.

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

They recorded only a 3*C delta between near black and white. Since white and chrome a much closer in performance, the delta would be within your margin or error.

The paint surface temperature between white and black can be around 40*C, where as white vs chrome is under 10*C.

Here's chrome on a white panel that I cut out of my old van:



Frankly, you don't need any test, you can easily feel the difference by hand. How much it affects interior temperature is another thing. I did my install on a van without any headliner (which would then get very hot solar panels on top), a black Jeep without headliner and an almost black car with headliner. Basically all worst case scenarios.

If you've got a silver car and a decent headliner, you'll probably see no measurable benefit. For example I insulated my doors, and the IR shows no difference.

You might notice a conspicuous absence of window tint testing (two cars side by side) on line. I can only conclude that such results are underwhelming - even if surface testing is impressive:

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

But this is ecomodder, where every bit adds up.

[oldtamiyaphile]

Originally Posted by seifrob

The reason behind white roofs is safety regulation, I guess. I asked local police about chrome roof and the answer was i would get pulled over for blinding other drivers.

It's about fashion & technology. In the 50s-60s (when white roofs were common pre A/C days) chrome wrap hadn't been invented. Actual chromium plated roofs would have been expensive.

Today wrap only lasts a few years, that's OK if you can DIY it, not so much for an OEM. Today's fashion happens to be for black painted roofs.

Ask your local police to show you the law that forbids chrome roofs. As them if it's the same one that bans large chrome moldings or polished tanker trucks.

Shadow chrome is also an option. It performs about half way between chrome and white - looks almost exactly like metallic grey paint.

[California98Civic]

Originally Posted by oldtamiyaphile

... Shadow chrome is also an option. It performs about half way between chrome and white - looks almost exactly like metallic grey paint.

I read the test article in the post above that you linked. Thanks. Seems tint and paint can each reduce internal peak temps by a few percent. I guess that is something, but I think those tests miss the fact that when a car is in motion the wind is cooling the car surface. White, black, pink, purple... at 60 mph does it really matter anymore? Tint on the other hand prevents heat from entering the car at any speed.

But I need a clarification: are you saying Shadow Chrome is heat rejecting/reflective? If so, what brands?

[cRiPpLe_rOoStEr]

Originally Posted by seifrob

actually, as far as I know, better than Land Rover white roof was their tropical roof. Essentially white metal roof about one inch above normal roof. It reflects sun radiation and the one-inch air gap prevents heat to be conducted to the car.

I've already seen a handful of those, but they're not so common here.